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Han Y, Kamau PM, Lai R, Luo L. Bioactive Peptides and Proteins from Centipede Venoms. Molecules 2022; 27:molecules27144423. [PMID: 35889297 PMCID: PMC9325314 DOI: 10.3390/molecules27144423] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 07/05/2022] [Accepted: 07/07/2022] [Indexed: 12/02/2022] Open
Abstract
Venoms are a complex cocktail of biologically active molecules, including peptides, proteins, polyamide, and enzymes widely produced by venomous organisms. Through long-term evolution, venomous animals have evolved highly specific and diversified peptides and proteins targeting key physiological elements, including the nervous, blood, and muscular systems. Centipedes are typical venomous arthropods that rely on their toxins primarily for predation and defense. Although centipede bites are frequently reported, the composition and effect of centipede venoms are far from known. With the development of molecular biology and structural biology, the research on centipede venoms, especially peptides and proteins, has been deepened. Therefore, we summarize partial progress on the exploration of the bioactive peptides and proteins in centipede venoms and their potential value in pharmacological research and new drug development.
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Affiliation(s)
- Yalan Han
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Sino-African Joint Research Center, and Engineering Laboratory of Peptides, Kunming Institute of Zoology, Kunming 650107, China; (Y.H.); (P.M.K.)
| | - Peter Muiruri Kamau
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Sino-African Joint Research Center, and Engineering Laboratory of Peptides, Kunming Institute of Zoology, Kunming 650107, China; (Y.H.); (P.M.K.)
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ren Lai
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Sino-African Joint Research Center, and Engineering Laboratory of Peptides, Kunming Institute of Zoology, Kunming 650107, China; (Y.H.); (P.M.K.)
- University of Chinese Academy of Sciences, Beijing 100049, China
- Center for Evolution and Conservation Biology, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
- Correspondence: (R.L.); (L.L.)
| | - Lei Luo
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Sino-African Joint Research Center, and Engineering Laboratory of Peptides, Kunming Institute of Zoology, Kunming 650107, China; (Y.H.); (P.M.K.)
- Correspondence: (R.L.); (L.L.)
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Frankowski K, Miyazaki K, Brenneis G. A microCT-based atlas of the central nervous system and midgut in sea spiders (Pycnogonida) sheds first light on evolutionary trends at the family level. Front Zool 2022; 19:14. [PMID: 35361245 PMCID: PMC8973786 DOI: 10.1186/s12983-022-00459-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 03/18/2022] [Indexed: 11/18/2022] Open
Abstract
Background Pycnogonida (sea spiders) is the sister group of all other extant chelicerates (spiders, scorpions and relatives) and thus represents an important taxon to inform early chelicerate evolution. Notably, phylogenetic analyses have challenged traditional hypotheses on the relationships of the major pycnogonid lineages (families), indicating external morphological traits previously used to deduce inter-familial affinities to be highly homoplastic. This erodes some of the support for phylogenetic information content in external morphology and calls for the study of additional data classes to test and underpin in-group relationships advocated in molecular analyses. In this regard, pycnogonid internal anatomy remains largely unexplored and taxon coverage in the studies available is limited. Results Based on micro-computed X-ray tomography and 3D reconstruction, we created a comprehensive atlas of in-situ representations of the central nervous system and midgut layout in all pycnogonid families. Beyond that, immunolabeling for tubulin and synapsin was used to reveal selected details of ganglionic architecture. The ventral nerve cord consistently features an array of separate ganglia, but some lineages exhibit extended composite ganglia, due to neuromere fusion. Further, inter-ganglionic distances and ganglion positions relative to segment borders vary, with an anterior shift in several families. Intersegmental nerves target longitudinal muscles and are lacking if the latter are reduced. Across families, the midgut displays linear leg diverticula. In Pycnogonidae, however, complex multi-branching diverticula occur, which may be evolutionarily correlated with a reduction of the heart. Conclusions Several gross neuroanatomical features are linked to external morphology, including intersegmental nerve reduction in concert with trunk segment fusion, or antero-posterior ganglion shifts in partial correlation to trunk elongation/compaction. Mapping on a recent phylogenomic phylogeny shows disjunct distributions of these traits. Other characters show no such dependency and help to underpin closer affinities in sub-branches of the pycnogonid tree, as exemplified by the tripartite subesophageal ganglion of Pycnogonidae and Rhynchothoracidae. Building on this gross anatomical atlas, future studies should now aim to leverage the full potential of neuroanatomy for phylogenetic interrogation by deciphering pycnogonid nervous system architecture in more detail, given that pioneering work on neuron subsets revealed complex character sets with unequivocal homologies across some families. Supplementary Information The online version contains supplementary material available at 10.1186/s12983-022-00459-8.
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Affiliation(s)
- Karina Frankowski
- Zoologisches Institut und Museum, AG Cytologie und Evolutionsbiologie, Universität Greifswald, Soldmannstraße 23, 17489, Greifswald, Germany
| | - Katsumi Miyazaki
- Department of Environmental Science, Faculty of Science, Niigata University, 8050 Ikarashi 2-no-cho, Niigata, 950-2181, Japan
| | - Georg Brenneis
- Zoologisches Institut und Museum, AG Cytologie und Evolutionsbiologie, Universität Greifswald, Soldmannstraße 23, 17489, Greifswald, Germany.
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Brenneis G. The visual pathway in sea spiders (Pycnogonida) displays a simple serial layout with similarities to the median eye pathway in horseshoe crabs. BMC Biol 2022; 20:27. [PMID: 35086529 PMCID: PMC8796508 DOI: 10.1186/s12915-021-01212-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 12/14/2021] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Phylogenomic studies over the past two decades have consolidated the major branches of the arthropod tree of life. However, especially within the Chelicerata (spiders, scorpions, and kin), interrelationships of the constituent taxa remain controversial. While sea spiders (Pycnogonida) are firmly established as sister group of all other extant representatives (Euchelicerata), euchelicerate phylogeny itself is still contested. One key issue concerns the marine horseshoe crabs (Xiphosura), which recent studies recover either as sister group of terrestrial Arachnida or nested within the latter, with significant impact on postulated terrestrialization scenarios and long-standing paradigms of ancestral chelicerate traits. In potential support of a nested placement, previous neuroanatomical studies highlighted similarities in the visual pathway of xiphosurans and some arachnopulmonates (scorpions, whip scorpions, whip spiders). However, contradictory descriptions of the pycnogonid visual system hamper outgroup comparison and thus character polarization. RESULTS To advance the understanding of the pycnogonid brain and its sense organs with the aim of elucidating chelicerate visual system evolution, a wide range of families were studied using a combination of micro-computed X-ray tomography, histology, dye tracing, and immunolabeling of tubulin, the neuropil marker synapsin, and several neuroactive substances (including histamine, serotonin, tyrosine hydroxylase, and orcokinin). Contrary to previous descriptions, the visual system displays a serial layout with only one first-order visual neuropil connected to a bilayered arcuate body by catecholaminergic interneurons. Fluorescent dye tracing reveals a previously reported second visual neuropil as the target of axons from the lateral sense organ instead of the eyes. CONCLUSIONS Ground pattern reconstruction reveals remarkable neuroanatomical stasis in the pycnogonid visual system since the Ordovician or even earlier. Its conserved layout exhibits similarities to the median eye pathway in euchelicerates, especially in xiphosurans, with which pycnogonids share two median eye pairs that differentiate consecutively during development and target one visual neuropil upstream of the arcuate body. Given multiple losses of median and/or lateral eyes in chelicerates, and the tightly linked reduction of visual processing centers, interconnections between median and lateral visual neuropils in xiphosurans and arachnopulmonates are critically discussed, representing a plausible ancestral condition of taxa that have retained both eye types.
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Affiliation(s)
- Georg Brenneis
- Universität Greifswald, Zoologisches Institut und Museum, AG Cytologie und Evolutionsbiologie, Soldmannstraße 23, 17489, Greifswald, Germany.
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Strausfeld NJ, Wolff GH, Sayre ME. Mushroom body evolution demonstrates homology and divergence across Pancrustacea. eLife 2020; 9:e52411. [PMID: 32124731 PMCID: PMC7054004 DOI: 10.7554/elife.52411] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 02/03/2020] [Indexed: 02/06/2023] Open
Abstract
Descriptions of crustacean brains have focused mainly on three highly derived lineages of malacostracans: the reptantian infraorders represented by spiny lobsters, lobsters, and crayfish. Those descriptions advocate the view that dome- or cap-like neuropils, referred to as 'hemiellipsoid bodies,' are the ground pattern organization of centers that are comparable to insect mushroom bodies in processing olfactory information. Here we challenge the doctrine that hemiellipsoid bodies are a derived trait of crustaceans, whereas mushroom bodies are a derived trait of hexapods. We demonstrate that mushroom bodies typify lineages that arose before Reptantia and exist in Reptantia thereby indicating that the mushroom body, not the hemiellipsoid body, provides the ground pattern for both crustaceans and hexapods. We show that evolved variations of the mushroom body ground pattern are, in some lineages, defined by extreme diminution or loss and, in others, by the incorporation of mushroom body circuits into lobeless centers. Such transformations are ascribed to modifications of the columnar organization of mushroom body lobes that, as shown in Drosophila and other hexapods, contain networks essential for learning and memory.
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Affiliation(s)
- Nicholas James Strausfeld
- Department of Neuroscience, School of Mind, Brain and BehaviorUniversity of ArizonaTucsonUnited States
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Maurer M, Hladik J, Iliffe TM, Stemme T. Histaminergic interneurons in the ventral nerve cord: assessment of their value for Euarthropod phylogeny. ZOOLOGICAL LETTERS 2019; 5:36. [PMID: 31890274 PMCID: PMC6929356 DOI: 10.1186/s40851-019-0151-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 12/12/2019] [Indexed: 06/10/2023]
Abstract
Despite numerous approaches to the resolution of euarthropod phylogeny, mainly based on modern sequence information and traditional external morphology, the resulting hypotheses are often contradictory and leave many questions about euarthropod evolution unanswered. The comparison of developmental and structural aspects of the nervous system has shown to be a valuable contribution to the assessment of current phylogenetic hypotheses. One promising approach for the generation of new character sets is the morphology of transmitter systems and the discovery of individually identifiable neurons, which allow phylogenetic comparisons on the single cell level. In this context, the serotonin transmitter system has been investigated to a considerable degree. Studies to date have yielded important stimuli to our understanding of euarthropod relationships and the evolution of their nervous systems. However, data on other transmitter systems remain fragmented, and their value with respect to phylogenetic questions remains speculative. The biogenic amine histamine is a promising transmitter; a substantial amount of data has been reported in the literature and the homology of some histaminergic neurons has been suggested. Here, we present a comprehensive review of histaminergic neurons in the ventral nerve cord of Euarthropoda. Using immunocytochemical labeling of histamine combined with confocal laser-scanning microscopy, we investigated the transmitter system in phylogenetically relevant taxa, such as Zygentoma, Remipedia, Diplopoda, and Arachnida. By reconstructing ground patterns, we evaluated the significance of this specific character set for euarthropod phylogeny. With this approach, we identified a set of neurons, which can be considered homologous within the respective major taxon. In conclusion, the histaminergic system contains useful information for our understanding of euarthropod phylogeny, supporting the proposed clades Tetraconata and Mandibulata. Furthermore, this character set has considerable potential to help resolve relationships within the major clades at a deeper level of taxonomy, due to the considerable variability in neurite morphology.
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Affiliation(s)
- Maite Maurer
- Institute of Neurobiology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Janina Hladik
- Institute of Neurobiology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Thomas M. Iliffe
- Department of Marine Biology, Texas A&M University at Galveston, 200 Seawolf Parkway, Galveston, TX 77553 USA
| | - Torben Stemme
- Institute of Neurobiology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Strausfeld NJ, Sayre ME. Mushroom bodies in Reptantia reflect a major transition in crustacean brain evolution. J Comp Neurol 2019; 528:261-282. [PMID: 31376285 DOI: 10.1002/cne.24752] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/27/2019] [Accepted: 07/30/2019] [Indexed: 11/11/2022]
Abstract
Brain centers possessing a suite of neuroanatomical characters that define mushroom bodies of dicondylic insects have been identified in mantis shrimps, which are basal malacostracan crustaceans. Recent studies of the caridean shrimp Lebbeus groenlandicus further demonstrate the existence of mushroom bodies in Malacostraca. Nevertheless, received opinion promulgates the hypothesis that domed centers called hemiellipsoid bodies typifying reptantian crustaceans, such as lobsters and crayfish, represent the malacostracan cerebral ground pattern. Here, we provide evidence from the marine hermit crab Pagurus hirsutiusculus that refutes this view. P. hirsutiusculus, which is a member of the infraorder Anomura, reveals a chimeric morphology that incorporates features of a domed hemiellipsoid body and a columnar mushroom body. These attributes indicate that a mushroom body morphology is the ancestral ground pattern, from which the domed hemiellipsoid body derives and that the "standard" reptantian hemiellipsoid bodies that typify Astacidea and Achelata are extreme examples of divergence from this ground pattern. This interpretation is underpinned by comparing the lateral protocerebrum of Pagurus with that of the crayfish Procambarus clarkii and Orconectes immunis, members of the reptantian infraorder Astacidea.
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Affiliation(s)
- Nicholas J Strausfeld
- Department of Neuroscience, School of Mind, Brain and Behavior, University of Arizona, Tucson, Arizona
| | - Marcel E Sayre
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden
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Sayre ME, Strausfeld NJ. Mushroom bodies in crustaceans: Insect-like organization in the caridid shrimp Lebbeus groenlandicus. J Comp Neurol 2019; 527:2371-2387. [PMID: 30861118 DOI: 10.1002/cne.24678] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 02/27/2019] [Accepted: 02/28/2019] [Indexed: 11/11/2022]
Abstract
Paired centers in the forebrain of insects, called the mushroom bodies, have become the most investigated brain region of any invertebrate due to novel genetic strategies that relate unique morphological attributes of these centers to their functional roles in learning and memory. Mushroom bodies possessing all the morphological attributes of those in dicondylic insects have been identified in mantis shrimps, basal hoplocarid crustaceans that are sister to Eumalacostraca, the most species-rich group of Crustacea. However, unless other examples of mushroom bodies can be identified in Eumalacostraca, the possibility is that mushroom body-like centers may have undergone convergent evolution in Hoplocarida and are unique to this crustacean lineage. Here, we provide evidence that speaks against convergent evolution, describing in detail the paired mushroom bodies in the lateral protocerebrum of a decapod crustacean, Lebbeus groenlandicus, a species belonging to the infraorder Caridea, an ancient lineage of Eumalacostraca.
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Affiliation(s)
- Marcel E Sayre
- Lund Vision Group, Department of Biology, Lund University, Lund, Sweden
| | - Nicholas J Strausfeld
- Department of Neuroscience, School of Mind, Brain and Behavior, University of Arizona, Tucson, Arizona
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Kenning M, Schendel V, Müller CHG, Sombke A. Comparative morphology of ultimate and walking legs in the centipede Lithobius forficatus (Myriapoda) with functional implications. ZOOLOGICAL LETTERS 2019; 5:3. [PMID: 30656061 PMCID: PMC6330759 DOI: 10.1186/s40851-018-0115-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 12/07/2018] [Indexed: 06/09/2023]
Abstract
BACKGROUND In the context of evolutionary arthopodial transformations, centipede ultimate legs exhibit a plethora of morphological modifications and behavioral adaptations. Many species possess significantly elongated, thickened, or pincer-like ultimate legs. They are frequently sexually dimorphic, indicating a role in courtship and mating. In addition, glandular pores occur more commonly on ultimate legs than on walking legs, indicating a role in secretion, chemical communication, or predator avoidance. In this framework, this study characterizes the evolutionarily transformed ultimate legs in Lithobius forficatus in comparison with regular walking legs. RESULTS A comparative analysis using macro-photography, SEM, μCT, autofluorescence, backfilling, and 3D-reconstruction illustrates that ultimate legs largely resemble walking legs, but also feature a series of distinctions. Substantial differences are found with regard to aspects of the configuration of specific podomeres, musculature, abundance of epidermal glands, typology and distribution of epidermal sensilla, and architecture of associated nervous system structures. CONCLUSION In consideration of morphological and behavioral characteristics, ultimate legs in L. forficatus primarily serve a defensive, but also a sensory function. Moreover, morphologically coherent characteristics in the organization of the ultimate leg versus the antenna-associated neuromere point to constructional constraints in the evolution of primary processing neuropils.
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Affiliation(s)
- Matthes Kenning
- Cytology and Evolutionary Biology, University of Greifswald, Zoological Institute and Museum, Soldmannstrasse 23, 17489 Greifswald, Germany
- General and Systematic Zoology, University of Greifswald, Zoological Institute and Museum, Loitzer Strasse 26, 17489 Greifswald, Germany
| | - Vanessa Schendel
- Cytology and Evolutionary Biology, University of Greifswald, Zoological Institute and Museum, Soldmannstrasse 23, 17489 Greifswald, Germany
- Centre for Advanced Imaging, The University of Queensland, Building 57, St. Lucia, Queensland 4072 Australia
| | - Carsten H. G. Müller
- General and Systematic Zoology, University of Greifswald, Zoological Institute and Museum, Loitzer Strasse 26, 17489 Greifswald, Germany
| | - Andy Sombke
- Cytology and Evolutionary Biology, University of Greifswald, Zoological Institute and Museum, Soldmannstrasse 23, 17489 Greifswald, Germany
- Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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Abstract
The discovery of fossilized brains and ventral nerve cords in lower and mid-Cambrian arthropods has led to crucial insights about the evolution of their central nervous system, the segmental identity of head appendages and the early evolution of eyes and their underlying visual systems. Fundamental ground patterns of lower Cambrian arthropod brains and nervous systems correspond to the ground patterns of brains and nervous systems belonging to three of four major extant panarthropod lineages. These findings demonstrate the evolutionary stability of early neural arrangements over an immense time span. Here, we put these fossil discoveries in the context of evidence from cladistics, as well as developmental and comparative neuroanatomy, which together suggest that despite many evolved modifications of neuropil centers within arthropod brains and ganglia, highly conserved arrangements have been retained. Recent phylogenies of the arthropods, based on fossil and molecular evidence, and estimates of divergence dates, suggest that neural ground patterns characterizing onychophorans, chelicerates and mandibulates are likely to have diverged between the terminal Ediacaran and earliest Cambrian, heralding the exuberant diversification of body forms that account for the Cambrian Explosion.
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Affiliation(s)
- Nicholas J Strausfeld
- Department of Neuroscience and Center for Insect Science, University of Arizona, Tucson, AZ 85721, USA.
| | - Xiaoya Ma
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK; Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China
| | - Gregory D Edgecombe
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK.
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Wolf H. Scorpions pectines - Idiosyncratic chemo- and mechanosensory organs. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:753-764. [PMID: 29061448 DOI: 10.1016/j.asd.2017.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 10/17/2017] [Accepted: 10/18/2017] [Indexed: 05/15/2023]
Abstract
Scorpions possess specialised chemosensory appendages, the pectines. These comb-shaped limbs are located ventrally behind the walking legs. Like the antennae of mandibulate arthropods, they also serve a mechanosensory function. However, more than 90% of the sometimes well above 100,000 sensory neurons projecting from a pectine to the central nervous system are chemosensory. There are two primary projection neuropils. The posterior one, immediately adjacent to the pectine nerve entrance, has an intriguing substructure reminiscent of the olfactory glomeruli observed in the primary chemosensory neuropils of many arthropods and indeed of most bilaterian animals. There are further similarities, particularly to the antennal lobes of mandibulate arthropods, including dense innervation by a relatively small number of putative serotonergic interneurons and the presence of GABA immunoreactivity, indicative of inhibitory interactions. Scorpion idiosyncrasies include the flattened shape and broad size range of the glomerulus-like neuropil compartments. Further, these compartments are often not clearly delimited and form layers in the neuropil that are arranged like onion peels. In summary, the pectine appendages of scorpions and their central nervous projections appear as promising study subjects, particularly regarding comparative examination of chemosensory representation and processing strategies. The possibility of combined, rather than discrete, representations of chemo- and mechanosensory inputs should merit further study.
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Affiliation(s)
- Harald Wolf
- Stellenbosch Institute for Advanced Study, Wallenberg Research Centre, 10 Marais Street, Stellenbosch 7600, South Africa.
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Sombke A, Stemme T. Serotonergic neurons in the ventral nerve cord of Chilopoda - a mandibulate pattern of individually identifiable neurons. ZOOLOGICAL LETTERS 2017; 3:9. [PMID: 28690866 PMCID: PMC5496589 DOI: 10.1186/s40851-017-0070-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 06/21/2017] [Indexed: 05/28/2023]
Abstract
BACKGROUND Given the numerous hypotheses concerning arthropod phylogeny, independent data are needed to supplement knowledge based on traditional external morphology and modern molecular sequence information. One promising approach involves comparisons of the structure and development of the nervous system. Along these lines, the morphology of serotonin-immunoreactive neurons in the ventral nerve cord has been investigated in numerous tetraconate taxa (Crustacea and Hexapoda). It has been shown that these neurons can be identified individually due to their comparably low number, characteristic soma position, and neurite morphology, thus making it possible to establish homologies at the single cell level. Within Chilopoda (centipedes), detailed analyses of major branching patterns of serotonin-immunoreactive neurons are missing, but are crucial for developing meaningful conclusions on the homology of single cells. RESULTS In the present study, we re-investigated the distribution and projection patterns of serotonin-immunoreactive neurons in the ventral nerve cord of three centipede species: Scutigera coleoptrata, Lithobius forficatus, and Scolopendra oraniensis. The centipede serotonergic system in the ventral nerve cord contains defined groups of individually identifiable neurons. An anterior and two posterior immunoreactive neurons per hemiganglion with contralateral projections, a pair of ipsilateral projecting lateral neurons (an autapomorphic character for Chilopoda), as well as a postero-lateral group of an unclear number of cells are present in the ground pattern of Chilopoda. CONCLUSIONS Comparisons to the patterns of serotonin-immunoreactive neurons of tetraconate taxa support the homology of anterior and posterior neurons. Our results thus support a sister group relationship of Myriapoda and Tetraconata and, further, a mandibulate ground pattern of individually identifiable serotonin-immunoreactive neurons in the ventral nerve cord. Medial neurons are not considered to be part of the tetraconate ground pattern, but could favor the 'Miracrustacea hypothesis', uniting Remipedia, Cephalocarida, and Hexapoda.
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Affiliation(s)
- Andy Sombke
- University of Greifswald, Zoological Institute and Museum, Cytology and Evolutionary Biology, Soldmannstrasse 23, 17487 Greifswald, Germany
| | - Torben Stemme
- Division of Cell Biology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15/102, 30173 Hannover, Germany
- Current address: University of Ulm, Institute for Neurobiology, Helmholtzstraße 10/1, 89081 Ulm, Germany
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Martin C, Gross V, Hering L, Tepper B, Jahn H, de Sena Oliveira I, Stevenson PA, Mayer G. The nervous and visual systems of onychophorans and tardigrades: learning about arthropod evolution from their closest relatives. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 203:565-590. [DOI: 10.1007/s00359-017-1186-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/02/2017] [Accepted: 05/29/2017] [Indexed: 12/19/2022]
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Ortega-Hernández J, Janssen R, Budd GE. Origin and evolution of the panarthropod head - A palaeobiological and developmental perspective. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:354-379. [PMID: 27989966 DOI: 10.1016/j.asd.2016.10.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2016] [Revised: 09/15/2016] [Accepted: 10/25/2016] [Indexed: 05/14/2023]
Abstract
The panarthropod head represents a complex body region that has evolved through the integration and functional specialization of the anterior appendage-bearing segments. Advances in the developmental biology of diverse extant organisms have led to a substantial clarity regarding the relationships of segmental homology between Onychophora (velvet worms), Tardigrada (water bears), and Euarthropoda (e.g. arachnids, myriapods, crustaceans, hexapods). The improved understanding of the segmental organization in panarthropods offers a novel perspective for interpreting the ubiquitous Cambrian fossil record of these successful animals. A combined palaeobiological and developmental approach to the study of the panarthropod head through deep time leads us to propose a consensus hypothesis for the intricate evolutionary history of this important tagma. The contribution of exceptionally preserved brains in Cambrian fossils - together with the recognition of segmentally informative morphological characters - illuminate the polarity for major anatomical features. The euarthropod stem-lineage provides a detailed view of the step-wise acquisition of critical characters, including the origin of a multiappendicular head formed by the fusion of several segments, and the transformation of the ancestral protocerebral limb pair into the labrum, following the postero-ventral migration of the mouth opening. Stem-group onychophorans demonstrate an independent ventral migration of the mouth and development of a multisegmented head, as well as the differentiation of the deutocerebral limbs as expressed in extant representatives. The anterior organization of crown-group Tardigrada retains several ancestral features, such as an anterior-facing mouth and one-segmented head. The proposed model aims to clarify contentious issues on the evolution of the panarthropod head, and lays the foundation from which to further address this complex subject in the future.
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Affiliation(s)
| | - Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala SE-752 36, Sweden
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala SE-752 36, Sweden
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Martin C, Gross V, Pflüger HJ, Stevenson PA, Mayer G. Assessing segmental versus non-segmental features in the ventral nervous system of onychophorans (velvet worms). BMC Evol Biol 2017; 17:3. [PMID: 28049417 PMCID: PMC5209844 DOI: 10.1186/s12862-016-0853-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/15/2016] [Indexed: 11/12/2022] Open
Abstract
Background Due to their phylogenetic position as one of the closest arthropod relatives, studies of the organisation of the nervous system in onychophorans play a key role for understanding the evolution of body segmentation in arthropods. Previous studies revealed that, in contrast to the arthropods, segmentally repeated ganglia are not present within the onychophoran ventral nerve cords, suggesting that segmentation is either reduced or might be incomplete in the onychophoran ventral nervous system. Results To assess segmental versus non-segmental features in the ventral nervous system of onychophorans, we screened the nerve cords for various markers, including synapsin, serotonin, gamma-aminobutyric acid, RFamide, dopamine, tyramine and octopamine. In addition, we performed retrograde fills of serially repeated commissures and leg nerves to localise the position of neuronal somata supplying those. Our data revealed a mixture of segmental and non-segmental elements within the onychophoran nervous system. Conclusions We suggest that the segmental ganglia of arthropods evolved by a gradual condensation of subsets of neurons either in the arthropod or the arthropod-tardigrade lineage. These findings are in line with the hypothesis of gradual evolution of segmentation in panarthropods and thus contradict a loss of ancestral segmentation within the onychophoran lineage. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0853-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christine Martin
- Department of Zoology, University of Kassel, Heinrich-Plett-Str. 40, D-34132, Kassel, Germany.
| | - Vladimir Gross
- Department of Zoology, University of Kassel, Heinrich-Plett-Str. 40, D-34132, Kassel, Germany
| | - Hans-Joachim Pflüger
- Institute of Biology, Neurobiology, Free University of Berlin, Königin-Luise-Str. 28-30, D-14195, Berlin, Germany
| | - Paul A Stevenson
- Physiology of Animals and Behaviour, Institute of Biology, University of Leipzig, Talstraße 33, D-04103, Leipzig, Germany
| | - Georg Mayer
- Department of Zoology, University of Kassel, Heinrich-Plett-Str. 40, D-34132, Kassel, Germany
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Stemme T, Stern M, Bicker G. Serotonin-containing neurons in basal insects: In search of ground patterns among tetraconata. J Comp Neurol 2017; 525:79-115. [PMID: 27203729 DOI: 10.1002/cne.24043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 05/17/2016] [Accepted: 05/18/2016] [Indexed: 11/08/2022]
Abstract
The ventral nerve cord of Tetraconata contains a comparably low number of serotonin-immunoreactive neurons, facilitating individual identification of cells and their characteristic neurite morphology. This offers the rather unique possibility of establishing homologies at the single cell level. Because phylogenetic relationships within Tetraconata are still discussed controversially, comparisons of individually identifiable neurons can help to unravel these issues. Serotonin immunoreactivity has been investigated in numerous tetraconate taxa, leading to reconstructions of hypothetical ground patterns for major lineages. However, detailed descriptions of basal insects are still missing, but are crucial for meaningful evolutionary considerations. We investigated the morphology of individually identifiable serotonin-immunoreactive neurons in the ventral nerve cord of Zygentoma (Thermobia domestica, Lepisma saccharina, Atelura formicaria) and Archaeognatha (Machilis germanica, Dilta hibernica). To improve immunocytochemical resolution, we also performed preincubation experiments with 5-hydroxy-L-tryptophan and serotonin. Additionally, we checked for immunolabeling of tryptophan hydroxylase, an enzyme associated with the synthesis of serotonin. Besides the generally identified groups of anterolateral, medial, and posterolateral neurons within each ganglion of the ventral nerve cord, we identified several other immunoreactive cells, which seem to have no correspondence in other tetraconates. Furthermore, we show that not all immunoreactive neurons produce serotonin, but have the capability for serotonin uptake. Comparisons with the patterns of serotonin-containing neurons in major tetraconate taxa suggest a close phylogenetic relationship of Remipedia, Cephalocarida, and Hexapoda, supporting the Miracrustacea hypothesis. J. Comp. Neurol., 2016. © 2016 Wiley Periodicals, Inc. J. Comp. Neurol. 525:79-115, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Torben Stemme
- University of Veterinary Medicine Hannover, Division of Cell Biology, D-30173, Hannover, Germany
| | - Michael Stern
- University of Veterinary Medicine Hannover, Division of Cell Biology, D-30173, Hannover, Germany
| | - Gerd Bicker
- University of Veterinary Medicine Hannover, Division of Cell Biology, D-30173, Hannover, Germany
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Brenneis G, Scholtz G. Serotonin-immunoreactivity in the ventral nerve cord of Pycnogonida--support for individually identifiable neurons as ancestral feature of the arthropod nervous system. BMC Evol Biol 2015; 15:136. [PMID: 26156705 PMCID: PMC4496856 DOI: 10.1186/s12862-015-0422-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 06/23/2015] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND The arthropod ventral nerve cord features a comparably low number of serotonin-immunoreactive neurons, occurring in segmentally repeated arrays. In different crustaceans and hexapods, these neurons have been individually identified and even inter-specifically homologized, based on their soma positions and neurite morphologies. Stereotypic sets of serotonin-immunoreactive neurons are also present in myriapods, whereas in the investigated chelicerates segmental neuron clusters with higher and variable cell numbers have been reported. This led to the suggestion that individually identifiable serotonin-immunoreactive neurons are an apomorphic feature of the Mandibulata. To test the validity of this neurophylogenetic hypothesis, we studied serotonin-immunoreactivity in three species of Pycnogonida (sea spiders). This group of marine arthropods is nowadays most plausibly resolved as sister group to all other extant chelicerates, rendering its investigation crucial for a reliable reconstruction of arthropod nervous system evolution. RESULTS In all three investigated pycnogonids, the ventral walking leg ganglia contain different types of serotonin-immunoreactive neurons, the somata of which occurring mostly singly or in pairs within the ganglionic cortex. Several of these neurons are readily and consistently identifiable due to their stereotypic soma position and characteristic neurite morphology. They can be clearly homologized across different ganglia and different specimens as well as across the three species. Based on these homologous neurons, we reconstruct for their last common ancestor (presumably the pycnogonid stem species) a minimal repertoire of at least seven identified serotonin-immunoreactive neurons per hemiganglion. Beyond that, each studied species features specific pattern variations, which include also some neurons that were not reliably labeled in all specimens. CONCLUSIONS Our results unequivocally demonstrate the presence of individually identifiable serotonin-immunoreactive neurons in the pycnogonid ventral nerve cord. Accordingly, the validity of this neuroanatomical feature as apomorphy of Mandibulata is questioned and we suggest it to be ancestral for arthropods instead. The pronounced disparities between the segmental pattern in pycnogonids and the one of studied euchelicerates call for denser sampling within the latter taxon. By contrast, overall similarities between the pycnogonid and myriapod patterns may be indicative of single cell homologies in these two taxa. This notion awaits further substantiation from future studies.
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Affiliation(s)
- Georg Brenneis
- Humboldt-Universität zu Berlin, Institut für Biologie/Vergleichende Zoologie, Philippstraße 13, 10115, Berlin, Germany.
| | - Gerhard Scholtz
- Humboldt-Universität zu Berlin, Institut für Biologie/Vergleichende Zoologie, Philippstraße 13, 10115, Berlin, Germany.
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Gross V, Mayer G. Neural development in the tardigrade Hypsibius dujardini based on anti-acetylated α-tubulin immunolabeling. EvoDevo 2015; 6:12. [PMID: 26052416 PMCID: PMC4458024 DOI: 10.1186/s13227-015-0008-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/02/2015] [Indexed: 12/15/2022] Open
Abstract
Background The tardigrades (water bears) are a cosmopolitan group of microscopic ecdysozoans found in a variety of aquatic and temporarily wet environments. They are members of the Panarthropoda (Tardigrada + Onychophora + Arthropoda), although their exact position within this group remains contested. Studies of embryonic development in tardigrades have been scarce and have yielded contradictory data. Therefore, we investigated the development of the nervous system in embryos of the tardigrade Hypsibius dujardini using immunohistochemical techniques in conjunction with confocal laser scanning microscopy in an effort to gain insight into the evolution of the nervous system in panarthropods. Results An antiserum against acetylated α-tubulin was used to visualize the axonal processes and general neuroanatomy in whole-mount embryos of the eutardigrade H. dujardini. Our data reveal that the tardigrade nervous system develops in an anterior-to-posterior gradient, beginning with the neural structures of the head. The brain develops as a dorsal, bilaterally symmetric structure and contains a single developing central neuropil. The stomodeal nervous system develops separately and includes at least four separate, ring-like commissures. A circumbuccal nerve ring arises late in development and innervates the circumoral sensory field. The segmental trunk ganglia likewise arise from anterior to posterior and establish links with each other via individual pioneering axons. Each hemiganglion is associated with a number of peripheral nerves, including a pair of leg nerves and a branched, dorsolateral nerve. Conclusions The revealed pattern of brain development supports a single-segmented brain in tardigrades and challenges previous assignments of homology between tardigrade brain lobes and arthropod brain segments. Likewise, the tardigrade circumbuccal nerve ring cannot be homologized with the arthropod ‘circumoral’ nerve ring, suggesting that this structure is unique to tardigrades. Finally, we propose that the segmental ganglia of tardigrades and arthropods are homologous and, based on these data, favor a hypothesis that supports tardigrades as the sister group of arthropods. Electronic supplementary material The online version of this article (doi:10.1186/s13227-015-0008-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Vladimir Gross
- Animal Evolution and Development, Institute of Biology, University of Leipzig, Talstraße 33, 04103 Leipzig, Germany ; Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel, Germany
| | - Georg Mayer
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel, Germany
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Rogers SM, Ott SR. Differential activation of serotonergic neurons during short- and long-term gregarization of desert locusts. Proc Biol Sci 2015; 282:20142062. [PMID: 25520357 PMCID: PMC4298206 DOI: 10.1098/rspb.2014.2062] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Serotonin is a neurochemical with evolutionarily conserved roles in orchestrating nervous system function and behavioural plasticity. A dramatic example is the rapid transformation of desert locusts from cryptic asocial animals into gregarious crop pests that occurs when drought forces them to accumulate on dwindling resources, triggering a profound alteration of behaviour within just a few hours. The onset of crowding induces a surge in serotonin within their thoracic ganglia that is sufficient and necessary to induce the switch from solitarious to gregarious behaviour. To identify the neurons responsible, we have analysed how acute exposure to three gregarizing stimuli--crowding, touching the hind legs or seeing and smelling other locusts--and prolonged group living affect the expression of serotonin in individual neurons in the thoracic ganglia. Quantitative analysis of cell body immunofluorescence revealed three classes of neurons with distinct expressional responses. All ganglia contained neurons that responded to multiple gregarizing stimuli with increased expression. A second class showed increased expression only in response to intense visual and olfactory stimuli from conspecifics. Prolonged group living affected a third and entirely different set of neurons, revealing a two-tiered role of the serotonergic system as both initiator and substrate of socially induced plasticity. This demonstrates the critical importance of ontogenetic time for understanding the function of serotonin in the reorganization of behaviour.
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Affiliation(s)
- Stephen M Rogers
- School of Biological Sciences, University of Sydney, A08 Heydon-Laurence Building, New South Wales 2006, Australia
| | - Swidbert R Ott
- Department of Biology, University of Leicester, Adrian Building, University Road, Leicester LE1 7RH, UK
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Kaul-Strehlow S, Urata M, Minokawa T, Stach T, Wanninger A. Neurogenesis in directly and indirectly developing enteropneusts: of nets and cords. ORG DIVERS EVOL 2015. [PMID: 26225120 PMCID: PMC4514687 DOI: 10.1007/s13127-015-0201-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Concerning the evolution of deuterostomes, enteropneusts (acorn worms) occupy a pivotal role as they share some characteristics with chordates (e.g., tunicates and vertebrates) but are also closely related to echinoderms (e.g., sea urchin). The nervous system in particular can be a highly informative organ system for evolutionary inferences, and advances in fluorescent microscopy have revealed overwhelming data sets on neurogenesis in various clades. However, immunocytochemical descriptions of neurogenesis of juvenile enteropneusts are particularly scarce, impeding the reconstruction of nervous system evolution in this group. We followed morphogenesis of the nervous system in two enteropneust species, one with direct (Saccoglossus kowalevskii) and the other with indirect development (Balanoglossus misakiensis), using an antibody against serotonin and electron microscopy. We found that all serotonin-like immunoreactive (LIR) neurons in both species are bipolar ciliary neurons that are intercalated between other epidermal cells. Unlike the tornaria larva of B. misakiensis, the embryonic nervous system of S. kowalevskii lacks serotonin-LIR neurons in the apical region as well as an opisthotroch neurite ring. Comparative analysis of both species shows that the projections of the serotonin-LIR somata initially form a basiepidermal plexus throughout the body that disappears within the trunk region soon after settlement before the concentrated dorsal and ventral neurite bundles emerge. Our data reveal a highly conserved mode of neurogenesis in enteropneusts that is independent of the developing mode and is inferred to be a common feature for Enteropneusta. Moreover, all detected serotonin-LIR neurons are presumably receptor cells, and the absence of serotonin-LIR interneurons from the enteropneust nervous system, which are otherwise common in various bilaterian central nervous systems, is interpreted as a loss that might have occurred already in the last common ancestor of Ambulacraria.
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Affiliation(s)
- Sabrina Kaul-Strehlow
- Department of Integrative Zoology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
| | - Makoto Urata
- Takehara Marine Science Station, Setouchi Field Science Center, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima 725-0024 Japan
| | - Takuya Minokawa
- Research Center for Marine Biology, Tohoku University, Asamushi, Aomori, Aomori 039-3501 Japan
| | - Thomas Stach
- Institute for Biology, Humboldt-University Berlin, Philippstr. 13, 10115 Berlin, Germany
| | - Andreas Wanninger
- Department of Integrative Zoology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
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Francisco A, Nocelli RC, Fontanetti CS. The nervous system of the neotropical millipede Gymnostreptus olivaceus Schubart, 1944 (Spirostreptida, Spirostreptidae) shows an additional cell layer. ANIM BIOL 2015. [DOI: 10.1163/15707563-00002466] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This study presents a morphological description of the central nervous system of the neotropical millipede Gymnostreptus olivaceus and the first report of an outer cell layer surrounding the nervous system in Diplopoda. The nervous system of this species consists of a brain formed by the fusion of proto-, deuto- and tritocerebrum, as well as a ventral nerve cord with metamerically arranged ganglia that extends through the entire length of the animal’s body. The optic lobes, mushroom bodies and olfactory glomeruli of this species were located and described. As has been reported for other millipedes, the nervous system of G. olivaceus comprises a cortical layer in which three types of neurons could be identified and an inner region of neuropil, both of which are wrapped and protected by a perineurium and a neural lamella. However, more externally to the neural lamella, there is a discontinuous and irregular outer cell sheath layer containing distinctive cells whose function appears to be linked to the nutrition and protection of neurons.
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Affiliation(s)
- Annelise Francisco
- Departamento de Biologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Bela Vista, 13.506-900, Rio Claro, São Paulo, Brazil
| | - Roberta C.F. Nocelli
- Centro de Ciências Agrárias, Departamento de Ciências da Natureza, Matemática e Educação UFSCar, Via Anhanguera, Km 174, Araras, São Paulo, Brazil
| | - Carmem S. Fontanetti
- Departamento de Biologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Bela Vista, 13.506-900, Rio Claro, São Paulo, Brazil
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Stegner ME, Brenneis G, Richter S. The ventral nerve cord in Cephalocarida (Crustacea): New insights into the ground pattern of Tetraconata. J Morphol 2013; 275:269-94. [DOI: 10.1002/jmor.20213] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 08/28/2013] [Accepted: 09/06/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Martin E.J. Stegner
- Universität Rostock, Institut für Biowissenschaften, Allgemeine und Spezielle Zoologie, Universitätsplatz 2; 18055 Rostock Mecklenburg-Vorpommern Germany
| | - Georg Brenneis
- Universität Rostock, Institut für Biowissenschaften, Allgemeine und Spezielle Zoologie, Universitätsplatz 2; 18055 Rostock Mecklenburg-Vorpommern Germany
| | - Stefan Richter
- Universität Rostock, Institut für Biowissenschaften, Allgemeine und Spezielle Zoologie, Universitätsplatz 2; 18055 Rostock Mecklenburg-Vorpommern Germany
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Mayer G, Martin C, Rüdiger J, Kauschke S, Stevenson PA, Poprawa I, Hohberg K, Schill RO, Pflüger HJ, Schlegel M. Selective neuronal staining in tardigrades and onychophorans provides insights into the evolution of segmental ganglia in panarthropods. BMC Evol Biol 2013; 13:230. [PMID: 24152256 PMCID: PMC4015553 DOI: 10.1186/1471-2148-13-230] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Accepted: 10/16/2013] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Although molecular analyses have contributed to a better resolution of the animal tree of life, the phylogenetic position of tardigrades (water bears) is still controversial, as they have been united alternatively with nematodes, arthropods, onychophorans (velvet worms), or onychophorans plus arthropods. Depending on the hypothesis favoured, segmental ganglia in tardigrades and arthropods might either have evolved independently, or they might well be homologous, suggesting that they were either lost in onychophorans or are a synapomorphy of tardigrades and arthropods. To evaluate these alternatives, we analysed the organisation of the nervous system in three tardigrade species using antisera directed against tyrosinated and acetylated tubulin, the amine transmitter serotonin, and the invertebrate neuropeptides FMRFamide, allatostatin and perisulfakinin. In addition, we performed retrograde staining of nerves in the onychophoran Euperipatoides rowelli in order to compare the serial locations of motor neurons within the nervous system relative to the appendages they serve in arthropods, tardigrades and onychophorans. RESULTS Contrary to a previous report from a Macrobiotus species, our immunocytochemical and electron microscopic data revealed contralateral fibres and bundles of neurites in each trunk ganglion of three tardigrade species, including Macrobiotus cf. harmsworthi, Paramacrobiotus richtersi and Hypsibius dujardini. Moreover, we identified additional, extra-ganglionic commissures in the interpedal regions bridging the paired longitudinal connectives. Within the ganglia we found serially repeated sets of serotonin- and RFamid-like immunoreactive neurons. Furthermore, our data show that the trunk ganglia of tardigrades, which include the somata of motor neurons, are shifted anteriorly with respect to each corresponding leg pair, whereas no such shift is evident in the arrangement of motor neurons in the onychophoran nerve cords. CONCLUSIONS Taken together, these data reveal three major correspondences between the segmental ganglia of tardigrades and arthropods, including (i) contralateral projections and commissures in each ganglion, (ii) segmentally repeated sets of immunoreactive neurons, and (iii) an anteriorly shifted (parasegmental) position of ganglia. These correspondences support the homology of segmental ganglia in tardigrades and arthropods, suggesting that these structures were either lost in Onychophora or, alternatively, evolved in the tardigrade/arthropod lineage.
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Affiliation(s)
- Georg Mayer
- Animal Evolution and Development, Institute of Biology, University of Leipzig, Talstraße 33, D-04103 Leipzig, Germany
| | - Christine Martin
- Animal Evolution and Development, Institute of Biology, University of Leipzig, Talstraße 33, D-04103 Leipzig, Germany
| | - Jan Rüdiger
- Animal Evolution and Development, Institute of Biology, University of Leipzig, Talstraße 33, D-04103 Leipzig, Germany
| | - Susann Kauschke
- Animal Evolution and Development, Institute of Biology, University of Leipzig, Talstraße 33, D-04103 Leipzig, Germany
| | - Paul A Stevenson
- Physiology of Animals and Behavior, Institute of Biology, University of Leipzig, Talstraße 33,D-04103 Leipzig, Germany
| | - Izabela Poprawa
- Department of Animal Histology and Embryology, University of Silesia, Bankowa 9, 40-007 Katowice, Poland
| | - Karin Hohberg
- Senckenberg Museum of Natural History Görlitz, Am Museum 1, D-02826 Görlitz, Germany
| | - Ralph O Schill
- Biological Institute, Zoology, University of Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
| | - Hans-Joachim Pflüger
- Neurobiology, Institute of Biology, Freie Universität Berlin, Königin-Luise-Str. 28-30, D-14195 Berlin, Germany
| | - Martin Schlegel
- Molecular Evolution & Animal Systematics, Institute of Biology, University of Leipzig, Talstraße 33, D-04103 Leipzig, Germany
- German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig, Deutscher Platz 5e, D-04103 Leipzig, Germany
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Serotonin-immunoreactive neurons in the ventral nerve cord of Remipedia (Crustacea): support for a sister group relationship of Remipedia and Hexapoda? BMC Evol Biol 2013; 13:119. [PMID: 23758940 PMCID: PMC3687579 DOI: 10.1186/1471-2148-13-119] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 06/04/2013] [Indexed: 11/10/2022] Open
Abstract
Background Remipedia were initially seen as a primitive taxon within Pancrustacea based on characters considered ancestral, such as the homonomously segmented trunk. Meanwhile, several morphological and molecular studies proposed a more derived position of Remipedia within Pancrustacea, including a sister group relationship to Hexapoda. Because of these conflicting hypotheses, fresh data are crucial to contribute new insights into euarthropod phylogeny. The architecture of individually identifiable serotonin-immunoreactive neurons has successfully been used for phylogenetic considerations in Euarthropoda. Here, we identified neurons in three species of Remipedia with an antiserum against serotonin and compared our findings to reconstructed ground patterns in other euarthropod taxa. Additionally, we traced neurite connectivity and neuropil outlines using antisera against acetylated α-tubulin and synapsin. Results The ventral nerve cord of Remipedia displays a typical rope-ladder-like arrangement of separate metameric ganglia linked by paired longitudinally projecting connectives. The peripheral projections comprise an intersegmental nerve, consisting of two branches that fuse shortly after exiting the connectives, and the segmental anterior and posterior nerve. The distribution and morphology of serotonin-immunoreactive interneurons in the trunk segments is highly conserved within the remipede species we analyzed, which allows for the reconstruction of a ground pattern: two posterior and one anterior pair of serotonin-immunoreactive neurons that possess a single contralateral projection. Additionally, three pairs of immunoreactive neurons are found in the medial part of each hemiganglion. In one species (Cryptocorynetes haptodiscus), the anterior pair of immunoreactive neurons is missing. Conclusions The anatomy of the remipede ventral nerve cord with its separate metameric ganglia mirrors the external morphology of the animal’s trunk. The rope-ladder-like structure and principal architecture of the segmental ganglia in Remipedia corresponds closely to that of other Euarthropoda. A comparison of the serotonin-immunoreactive cell arrangement of Remipedia to reconstructed ground patterns of major euarthropod taxa supports a homology of the anterior and posterior neurons in Pancrustacea. These neurons in Remipedia possess unbranched projections across the midline, pointing towards similarities to the hexapod pattern. Our findings are in line with a growing number of phylogenetic investigations proposing Remipedia to be a rather derived crustacean lineage that perhaps has close affinities to Hexapoda.
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Stemme T, Iliffe TM, Bicker G, Harzsch S, Koenemann S. Serotonin immunoreactive interneurons in the brain of the Remipedia: new insights into the phylogenetic affinities of an enigmatic crustacean taxon. BMC Evol Biol 2012; 12:168. [PMID: 22947030 PMCID: PMC3497878 DOI: 10.1186/1471-2148-12-168] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 08/24/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Remipedia, a group of homonomously segmented, cave-dwelling, eyeless arthropods have been regarded as basal crustaceans in most early morphological and taxonomic studies. However, molecular sequence information together with the discovery of a highly differentiated brain led to a reconsideration of their phylogenetic position. Various conflicting hypotheses have been proposed including the claim for a basal position of Remipedia up to a close relationship with Malacostraca or Hexapoda. To provide new morphological characters that may allow phylogenetic insights, we have analyzed the architecture of the remipede brain in more detail using immunocytochemistry (serotonin, acetylated α-tubulin, synapsin) combined with confocal laser-scanning microscopy and image reconstruction techniques. This approach allows for a comprehensive neuroanatomical comparison with other crustacean and hexapod taxa. RESULTS The dominant structures of the brain are the deutocerebral olfactory neuropils, which are linked by the olfactory globular tracts to the protocerebral hemiellipsoid bodies. The olfactory globular tracts form a characteristic chiasm in the center of the brain. In Speleonectes tulumensis, each brain hemisphere contains about 120 serotonin immunoreactive neurons, which are distributed in distinct cell groups supplying fine, profusely branching neurites to 16 neuropilar domains. The olfactory neuropil comprises more than 300 spherical olfactory glomeruli arranged in sublobes. Eight serotonin immunoreactive neurons homogeneously innervate the olfactory glomeruli. In the protocerebrum, serotonin immunoreactivity revealed several structures, which, based on their position and connectivity resemble a central complex comprising a central body, a protocerebral bridge, W-, X-, Y-, Z-tracts, and lateral accessory lobes. CONCLUSIONS The brain of Remipedia shows several plesiomorphic features shared with other Mandibulata, such as deutocerebral olfactory neuropils with a glomerular organization, innervations by serotonin immunoreactive interneurons, and connections to protocerebral neuropils. Also, we provided tentative evidence for W-, X-, Y-, Z-tracts in the remipedian central complex like in the brain of Malacostraca, and Hexapoda. Furthermore, Remipedia display several synapomorphies with Malacostraca supporting a sister group relationship between both taxa. These homologies include a chiasm of the olfactory globular tract, which connects the olfactory neuropils with the lateral protocerebrum and the presence of hemiellipsoid bodies. Even though a growing number of molecular investigations unites Remipedia and Cephalocarida, our neuroanatomical comparison does not provide support for such a sister group relationship.
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Affiliation(s)
- Torben Stemme
- Division of Cell Biology, University of Veterinary Medicine Hannover, Hannover, Germany
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Serotonin-immunoreactive neurons in scorpion pectine neuropils: similarities to insect and crustacean primary olfactory centres? ZOOLOGY 2012; 115:151-9. [PMID: 22445574 DOI: 10.1016/j.zool.2011.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 10/17/2011] [Accepted: 10/20/2011] [Indexed: 11/23/2022]
Abstract
The pectines of scorpions are a single pair of mechano- and chemosensory appendages located ventrally behind the most posterior pair of walking legs. They are used for probing the substrate in behaviours such as prey tracking and courtship. The sensory afferents on the pectines supply large segmental neuropils with a conspicuous glomerular structure. The pectine neuropils thus bear similarities to insect and crustacean deutocerebral chemosensory centres associated with the antennae, but they also possess idiosyncratic features. One characteristic property of many insect and decapod crustacean olfactory neuropils is their innervation by single, or very few, large serotonergic (inter-) neurons. This feature, among others, has been proposed to support homology of the olfactory lobes in the two arthropod groups. A possible serotonergic innervation of the scorpion pectine neuropils has not yet been studied, despite its apparent diagnostic and functional importance. We thus examined serotonin-immunoreactivity in the pectine neuropils of Androctonus australis and Pandinus imperator. Both scorpion species yielded similar results. The periphery of the neuropil and the matrix between the glomeruli are supplied by a dense network of serotonin-immunoreactive (5-HT-ir) arborisations and varicosities, while the glomeruli themselves are mostly free of 5-HT-ir fibres. The 5-HT-ir supply of the pectine neuropils has two origins. The first is a pair of neurons on each body side, up to 30 μm in diameter and thus slightly larger than the surrounding somata. These cell bodies are and associated with the neuromeres of the genital and pectine segments. The situation is reminiscent of the 5-HT supply of insect and crustacean olfactory and antennal neuropils. The second 5-HT innervation of the pectine neuropils is from a group of some 10-20 ipsilateral neuronal somata of slightly smaller size (15-20 μm). These are part of a much larger 5-HT-ir group comprising 70-90 somata. The whole group is located more anteriorly than the single soma mentioned above, and associated with the neuromere of the last (4th) walking leg. When compared to data from other arthropods, our findings may suggest that glomerular organisation is an ancestral feature of primary chemosensory centres innervated by arthropod appendages. This idea needs further scrutiny, although supporting evidence may have been overlooked previously, due to the small size of chemosensory neuropils in walking legs and in reduced segmental appendages.
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Groh C, Mayer G. Evolution of the arthropod nervous system. ARTHROPOD STRUCTURE & DEVELOPMENT 2011; 40:191-192. [PMID: 21679883 DOI: 10.1016/j.asd.2011.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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Whitington PM, Mayer G. The origins of the arthropod nervous system: insights from the Onychophora. ARTHROPOD STRUCTURE & DEVELOPMENT 2011; 40:193-209. [PMID: 21315833 DOI: 10.1016/j.asd.2011.01.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 01/17/2011] [Accepted: 01/25/2011] [Indexed: 05/30/2023]
Abstract
A revision of evolutionary relationships of the Arthropoda has provided fresh impetus to tracing the origins of the nervous system of this group of animals: other members of the Ecdysozoa possess a markedly different type of nervous system from both the arthropods and the annelid worms, with which they were previously grouped. Given their status as favoured sister taxon of the arthropods, Onychophora (velvet worms) are a key group for understanding the evolutionary changes that have taken place in the panarthropod (Arthropoda + Onychophora + Tardigrada) lineage. This article reviews our current knowledge of the structure and development of the onychophoran nervous system. The picture that emerges from these studies is that the nervous system of the panarthropod ancestor was substantially different from that of modern arthropods: this animal probably possessed a bipartite, rather than a tripartite brain; its nerve cord displayed only a limited degree of segmentation; and neurons were more numerous but more uniform in morphology than in living arthropods. These observations suggest an evolutionary scenario, by which the arthropod nervous system evolved from a system of orthogonally crossing nerve tracts present in both a presumed protostome ancestor and many extant worm-like invertebrates, including the onychophorans.
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Affiliation(s)
- Paul M Whitington
- Department of Anatomy and Cell Biology, University of Melbourne, Victoria 3010, Australia.
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Strausfeld NJ, Andrew DR. A new view of insect-crustacean relationships I. Inferences from neural cladistics and comparative neuroanatomy. ARTHROPOD STRUCTURE & DEVELOPMENT 2011; 40:276-88. [PMID: 21333750 DOI: 10.1016/j.asd.2011.02.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Revised: 01/28/2011] [Accepted: 02/08/2011] [Indexed: 05/15/2023]
Abstract
Traditional hypotheses regarding the relationships of the major arthropod lineages focus on suites of comparable characters, often those that address features of the exoskeleton. However, because of the enormous morphological variety among arthropods, external characters may lead to ambiguities of interpretation and definition, particularly when species have undergone evolutionary simplification and reversal. Here we present the results of a cladistic analysis using morphological characters associated with brains and central nervous systems, based on the evidence that cerebral organization is generally robust over geological time. Well-resolved, strongly supported phylogenies were obtained from a neuromorphological character set representing a variety of discrete neuroanatomical traits. Phylogenetic hypotheses from this analysis support many accepted relationships, including monophyletic Chelicerata, Myriapoda, and Hexapoda, paraphyletic Crustacea and the union of Hexapoda and Crustacea (Tetraconata). They also support Mandibulata (Myriapoda + Tetraconata). One problematic result, which can be explained by symplesiomorphies that are likely to have evolved in deep time, is the inability to resolve Onychophora as a taxon distinct from Arthropoda. Crucially, neuronal cladistics supports the heterodox conclusion that both Hexapoda and Malacostraca are derived from a common ancestor that possessed a suite of discrete neural centers comprising an elaborate brain. Remipedes and copepods, both resolved as basal to Branchiopoda share a neural ground pattern with Malacostraca. These findings distinguish Hexapoda (Insecta) from Branchiopoda, which is the sister group of the clade Malacostraca + Hexapoda. The present study resolves branchiopod crustaceans as descendents of an ancestor with a complex brain, which means that they have evolved secondary simplification and the loss or reduction of numerous neural systems.
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Affiliation(s)
- Nicholas J Strausfeld
- Department of Neuroscience, University of Arizona, 1040 E. 4th St., Gould-Simpson Bldg. #611, Tucson, AZ 85721, USA.
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Eriksson BJ, Stollewerk A. The morphological and molecular processes of onychophoran brain development show unique features that are neither comparable to insects nor to chelicerates. ARTHROPOD STRUCTURE & DEVELOPMENT 2010; 39:478-490. [PMID: 20696271 DOI: 10.1016/j.asd.2010.07.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 07/25/2010] [Accepted: 07/27/2010] [Indexed: 05/29/2023]
Abstract
The phylogenetic position of onychophorans is still being debated; however, most phylogenies suggest that onychophorans are a sister group to the arthropods. Here we have analysed neurogenesis in the brain of the onychophoran Euperipatoides kanangrensis. We show that the development of the onychophoran brain is considerably different from arthropods. Neural precursors seem to be generated at random positions rather than in distinct spatio-temporal domains as has been shown in insects and chelicerates. The different mode of neural precursor formation is reflected in the homogenous expression of the proneural and neurogenic genes. Furthermore, the morphogenetic events that generate the three-dimensional structure of the onychophoran brain are significantly different from arthropods. Despite the different mode of neural precursor formation in insects and chelicerates (neuroblasts versus neural precursor groups), brain neurogenesis shares more similarities in these arthropods as compared to the onychophoran. Our data show that the developmental processes that generate the brain have considerably diverged in onychophorans and arthropods.
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Affiliation(s)
- Bo Joakim Eriksson
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, UK.
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Immunohistochemical mapping of histamine, dopamine, and serotonin in the central nervous system of the copepod Calanus finmarchicus (Crustacea; Maxillopoda; Copepoda). Cell Tissue Res 2010; 341:49-71. [PMID: 20532915 DOI: 10.1007/s00441-010-0974-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 03/30/2010] [Indexed: 01/08/2023]
Abstract
Calanoid copepods constitute an important group of marine planktonic crustaceans that often dominate the metazoan biomass of the world's oceans. In proportion to their ecological importance, little is known about their nervous systems. We have used immunohistochemical techniques in a common North Atlantic calanoid to localize re-identifiable neurons that putatively contain the biogenic amines histamine, dopamine, and serotonin. We have found low numbers of such cells and cell groups (approximately 37 histamine pairs, 22 dopamine pairs, and 12 serotonin pairs) compared with those in previously described crustaceans. These cells are concentrated in the anterior part of the central nervous system, the majority for each amine being located in the three neuromeres that constitute the brain (protocerebrum, deutocerebrum, and tritocerebrum). Extensive histamine labeling occurs in several small compact protocerebral neuropils, three pairs of larger, more posterior, paired, dense neuropils, and one paired diffuse tritocerebral neuropil. The most concentrated neuropil showing dopamine labeling lies in the putative deutocerebrum, associated with heavily labeled commissural connections between the two sides of the brain. The most prominent serotonin neuropil is present in the anterior medial part of the brain. Tracts of immunoreactive fibers of all three amines are prominent in the cephalic region of the nervous system, but some projections into the most posterior thoracic regions have also been noted.
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Brenneis G, Richter S. Architecture of the nervous system in mystacocarida (Arthropoda, crustacea)--an immunohistochemical study and 3D reconstruction. J Morphol 2010; 271:169-89. [PMID: 19708064 DOI: 10.1002/jmor.10789] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mystacocarida is a species-poor group of minute crustaceans with unclear phylogenetic affinities. Previous studies have highlighted the putative "primitiveness" of several mystacocarid features, including the architecture of the nervous system. Recent studies on arthropod neuroarchitecture have provided a wealth of characters valuable for phylogenetic reconstructions. To permit and facilitate comparison with these data, we used immunohistochemical labeling (against acetylated alpha-tubulin, serotonin and FMRFamide) on the mystacocarid Derocheilocaris remanei, analyzing it with confocal laser-scanning microscopy and 3D reconstruction. The mystacocarid brain is fairly elongated, exhibiting a complicated stereotypic arrangement of neurite bundles. However, none of the applied markers provided evidence of structured neuropils such as a central body or olfactory glomeruli. A completely fused subesophageal ganglion is not present, all segmental soma clusters of the respective neuromeres still being delimitable. The distinct mandibular commissure comprises neurite bundles from more anterior regions, leading us to propose that it may have fused with an ancestral posterior tritocerebral commissure. The postcephalic ventral nervous system displays a typical ladder-like structure with separated ganglia which bears some resemblance to larval stages in other crustaceans. Ganglia and commissures are also present in the first three limbless "abdominal" segments, which casts doubt on the notion of a clear-cut distinction between thorax and abdomen. An unpaired longitudinal median neurite bundle is present and discussed as a potential tetraconate autapomorphy. Additionally, a paired latero-longitudinal neurite bundle extends along the trunk. It is connected to the intersegmental nerves and most likely fulfils neurohemal functions. We report the complete absence of serotonin-ir neurons in the ventral nervous system, which is a unique condition in arthropods and herein interpreted as a derived character.
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Affiliation(s)
- Georg Brenneis
- Universität Rostock, Institut für Biowissenschaften/Allgemeine und Spezielle Zoologie, Universitätsplatz 2, 18055 Rostock, Germany
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Edgecombe GD. Arthropod phylogeny: an overview from the perspectives of morphology, molecular data and the fossil record. ARTHROPOD STRUCTURE & DEVELOPMENT 2010; 39:74-87. [PMID: 19854297 DOI: 10.1016/j.asd.2009.10.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 10/12/2009] [Accepted: 10/14/2009] [Indexed: 05/03/2023]
Abstract
Monophyly of Arthropoda is emphatically supported from both morphological and molecular perspectives. Recent work finds Onychophora rather than Tardigrada to be the closest relatives of arthropods. The status of tardigrades as panarthropods (rather than cycloneuralians) is contentious from the perspective of phylogenomic data. A grade of Cambrian taxa in the arthropod stem group includes gilled lobopodians, dinocaridids (e.g., anomalocaridids), fuxianhuiids and canadaspidids that inform on character acquisition between Onychophora and the arthropod crown group. A sister group relationship between Crustacea (itself likely paraphyletic) and Hexapoda is retrieved by diverse kinds of molecular data and is well supported by neuroanatomy. This clade, Tetraconata, can be dated to the early Cambrian by crown group-type mandibles. The rival Atelocerata hypothesis (Myriapoda+Hexapoda) has no molecular support. The basal node in the arthropod crown group is embroiled in a controversy over whether myriapods unite with chelicerates (Paradoxopoda or Myriochelata) or with crustaceans and hexapods (Mandibulata). Both groups find some molecular and morphological support, though Mandibulata is presently the stronger morphological hypothesis. Either hypothesis forces an unsampled ghost lineage for Myriapoda from the Cambrian to the mid Silurian.
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Affiliation(s)
- Gregory D Edgecombe
- Department of Palaeontology, Natural History Museum, Cromwell Road, London, UK.
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Shear WA, Edgecombe GD. The geological record and phylogeny of the Myriapoda. ARTHROPOD STRUCTURE & DEVELOPMENT 2010; 39:174-190. [PMID: 19944188 DOI: 10.1016/j.asd.2009.11.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 11/18/2009] [Indexed: 05/28/2023]
Abstract
We review issues of myriapod phylogeny, from the position of the Myriapoda amongst arthropods to the relationships of the orders of the classes Chilopoda and Diplopoda. The fossil record of each myriapod class is reviewed, with an emphasis on developments since 1997. We accept as working hypotheses that Myriapoda is monophyletic and belongs in Mandibulata, that the classes of Myriapoda are monophyletic, and that they are related as (Chilopoda (Symphyla (Diplopoda+Pauropoda))). The most pressing challenges to these hypotheses are some molecular and developmental evidence for an alliance between myriapods and chelicerates, and the attraction of symphylans to pauropods in some molecular analyses. While the phylogeny of the orders of Chilopoda appears settled, the relationships within Diplopoda remain unclear at several levels. Chilopoda and Diplopoda have a relatively sparse representation as fossils, and Symphyla and Pauropoda fossils are known only from Tertiary ambers. Fossils are difficult to place in trees based on living forms because many morphological characters are not very likely to be preserved in the fossils; as a consequence, most diplopod fossils have been placed in extinct higher taxa. Nevertheless, important information from diplopod fossils includes the first documented occurrence of air-breathing, and the first evidence for the use of a chemical defense. Stem-group myriapods are unknown, but evidence suggests the group must have arisen in the Early Cambrian, with a major period of cladogenesis in the Late Ordovician and early Silurian. Large terrestrial myriapods were on land at least by mid-Silurian.
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Affiliation(s)
- William A Shear
- Department of Biology, Hampden-Sydney College, 200 Via Sacra, Hampden-Sydney, VA 23943, USA.
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Mayer G, Whitington PM. Neural development in Onychophora (velvet worms) suggests a step-wise evolution of segmentation in the nervous system of Panarthropoda. Dev Biol 2009; 335:263-75. [PMID: 19683520 DOI: 10.1016/j.ydbio.2009.08.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 08/02/2009] [Accepted: 08/10/2009] [Indexed: 12/20/2022]
Abstract
A fundamental question in biology is how animal segmentation arose during evolution. One particular challenge is to clarify whether segmental ganglia of the nervous system evolved once, twice, or several times within the Bilateria. As close relatives of arthropods, Onychophora play an important role in this debate since their nervous system displays a mixture of both segmental and non-segmental features. We present evidence that the onychophoran "ventral organs," previously interpreted as segmental anlagen of the nervous system, do not contribute to nerve cord formation and therefore cannot be regarded as vestiges of segmental ganglia. The early axonal pathways in the central nervous system arise by an anterior-to-posterior cascade of axonogenesis from neuronal cell bodies, which are distributed irregularly along each presumptive ventral cord. This pattern contrasts with the strictly segmental neuromeres present in arthropod embryos and makes the assumption of a secondary loss of segmentation in the nervous system during the evolution of the Onychophora less plausible. We discuss the implications of these findings for the evolution of neural segmentation in the Panarthropoda (Arthropoda+Onychophora+Tardigrada). Our data best support the hypothesis that the ancestral panarthropod had only a partially segmented nervous system, which evolved progressively into the segmental chain of ganglia seen in extant tardigrades and arthropods.
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Affiliation(s)
- Georg Mayer
- Department of Anatomy and Cell Biology, University of Melbourne, Victoria 3010, Australia.
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Engrailed-like immunoreactivity in the embryonic ventral nerve cord of the Marbled Crayfish (Marmorkrebs). INVERTEBRATE NEUROSCIENCE 2008; 8:177-97. [PMID: 19005710 DOI: 10.1007/s10158-008-0081-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Accepted: 10/27/2008] [Indexed: 10/21/2022]
Abstract
The homeobox transcription factor Engrailed is involved in controlling segmentation during arthropod germ band formation but also in establishing individual neuronal identities during later embryogenesis. In Crustacea, most studies analysing the expression of Engrailed so far have focussed on its function as segment polarity gene. In continuation to these previous studies, we analysed the neuronal expression of the Engrailed protein by immunohistochemistry in the embryonic nerve cord of a parthenogenetic crustacean, the Marbled Crayfish (Marmorkrebs). We paid particular attention to the individual identification of Engrailed expressing putative neuroblasts in the crayfish embryos. Engrailed positive cells in the neuroectoderm were counted, measured and mapped from 38 to 65% of embryonic development. That way, several Engrailed positive putative neuroblasts and putative neurons were identified. Our findings are compared with earlier studies on Engrailed expression during germ band formation in Crustacea. Recent data on neurogenesis in an amphipod crustacean have provided compelling evidence for the homology of several identified neuroblasts between this amphipod and insects. The present report may serve as a basis to explore the question if during crustacean neurogenesis additional communalities with insects exist.
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Telford MJ, Bourlat SJ, Economou A, Papillon D, Rota-Stabelli O. The evolution of the Ecdysozoa. Philos Trans R Soc Lond B Biol Sci 2008; 363:1529-37. [PMID: 18192181 DOI: 10.1098/rstb.2007.2243] [Citation(s) in RCA: 169] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ecdysozoa is a clade composed of eight phyla: the arthropods, tardigrades and onychophorans that share segmentation and appendages and the nematodes, nematomorphs, priapulids, kinorhynchs and loriciferans, which are worms with an anterior proboscis or introvert. Ecdysozoa contains the vast majority of animal species and there is a great diversity of body plans among both living and fossil members. The monophyly of the clade has been called into question by some workers based on analyses of whole genome datasets. We review the evidence that now conclusively supports the unique origin of these phyla. Relationships within Ecdysozoa are also controversial and we discuss the molecular and morphological evidence for a number of monophyletic groups within this superphylum.
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Mayer G, Harzsch S. Distribution of serotonin in the trunk of Metaperipatus blainvillei (Onychophora, Peripatopsidae): implications for the evolution of the nervous system in Arthropoda. J Comp Neurol 2008; 507:1196-208. [PMID: 18181152 DOI: 10.1002/cne.21603] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Onychophora ("velvet worms") are a key taxon in the discussion of arthropod phylogeny. Studies that analyze neuroanatomical characters against a phylogenetic background have recently provided new insights into this debate. However, to date only a few studies on nervous system organization, particularly in the trunk, are available in Onychophora. To close this gap and to compare the onychophoran nervous system with that of other bilaterians, we have analyzed the pattern of serotonin-like immunoreactivity in Metaperipatus blainvillei (Peripatopsidae). In addition to confirming previous histological observations, our experiments revealed many new aspects of nervous system organization in Onychophora. The serotonergic nervous system of M. blainvillei consists of five longitudinal nerve strands (the paired dorsolateral nerves, the heart nerve, and the paired ventral cords), which are interconnected at regular intervals by ring commissures as well as median commissures. The ring commissures are absent in the leg-bearing regions. In addition to the main nerve tracts, there are several extensive fiber networks innervating the integument, the nephridial organs, and the body musculature. The leg nerves and nephridial nerves represent the only strictly segmental neuronal structures. We conclude that the general architecture of the onychophoran nervous system in the trunk closely resembles the orthogonal organization that is present in various other groups of Bilateria, which suggests that the arthropod nervous system is derived from such an orthogonal pattern. This finding implies that the "rope ladder-like" nervous system may have arisen independently in Panarthropoda and Annelida and does not represent a synapomorphy of these groups.
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Affiliation(s)
- Georg Mayer
- Department of Anatomy and Cell Biology, University of Melbourne, Victoria 3010, Australia.
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Rieger V, Harzsch S. Embryonic development of the histaminergic system in the ventral nerve cord of the Marbled Crayfish (Marmorkrebs). Tissue Cell 2007; 40:113-26. [PMID: 18067933 DOI: 10.1016/j.tice.2007.10.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Revised: 10/22/2007] [Accepted: 10/22/2007] [Indexed: 11/27/2022]
Abstract
The embryonic development of neurotransmitter systems in crustaceans so far is poorly understood. Therefore, in the current study we monitored the ontogeny of histamine-immunoreactive neurons in the ventral nerve cord of the Marbled Crayfish, an emerging crustacean model system for developmental studies. The first histaminergic neurons arise around 60% of embryonic development, well after the primordial axonal scaffold of the ventral nerve cord has been established. This suggests that histaminergic neurons do not serve as pioneer neurons but that their axons follow well established axonal tracts. The developmental sequence of the different types of histaminergic neurons is charted in this study. The analysis of the histaminergic structures is also extended into adult specimens, showing a persistence of embryonic histaminergic neurons into adulthood. Our data are compared to the pattern of histaminergic neurons in other crustaceans and discussed with regard to our knowledge on other aspects of neurogenesis in Crustacea. Furthermore, the possible role of histaminergic neurons as characters in evolutionary considerations is evaluated.
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Affiliation(s)
- V Rieger
- Universität Ulm, Fakultät für Naturwissenschaften, Institut für Neurobiologie, D-89081 Ulm, Germany
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Three-dimensional reconstruction of the central nervous system of Macrobiotus hufelandi (Eutardigrada, Parachela): implications for the phylogenetic position of Tardigrada. ZOOMORPHOLOGY 2007. [DOI: 10.1007/s00435-007-0045-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Mayer G, Harzsch S. Immunolocalization of serotonin in Onychophora argues against segmental ganglia being an ancestral feature of arthropods. BMC Evol Biol 2007; 7:118. [PMID: 17629937 PMCID: PMC1933538 DOI: 10.1186/1471-2148-7-118] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Accepted: 07/15/2007] [Indexed: 11/10/2022] Open
Abstract
Background Onychophora (velvet worms) represent the most basal arthropod group and play a pivotal role in the current discussion on the evolution of nervous systems and segmentation in arthropods. Although there is a wealth of information on the immunolocalization of serotonin (5-hydroxytryptamine, 5-HT) in various euarthropods, as yet no comparable localization data are available for Onychophora. In order to understand how the onychophoran nervous system compares to that of other arthropods, we studied the distribution of serotonin-like immunoreactive neurons and histological characteristics of ventral nerve cords in Metaperipatus blainvillei (Onychophora, Peripatopsidae) and Epiperipatus biolleyi (Onychophora, Peripatidae). Results We demonstrate that paired leg nerves are the only segmental structures associated with the onychophoran nerve cord. Although the median commissures and peripheral nerves show a repeated pattern, their arrangement is independent from body segments characterized by the position of legs and associated structures. Moreover, the somata of serotonin-like immunoreactive neurons do not show any ordered arrangement in both species studied but are instead scattered throughout the entire length of each nerve cord. We observed neither a serially iterated nor a bilaterally symmetric pattern, which is in contrast to the strictly segmental arrangement of serotonergic neurons in other arthropods. Conclusion Our histological findings and immunolocalization experiments highlight the medullary organization of the onychophoran nerve cord and argue against segmental ganglia of the typical euarthropodan type being an ancestral feature of Onychophora. These results contradict a priori assumptions of segmental ganglia being an ancestral feature of arthropods and, thus, weaken the traditional Articulata hypothesis, which proposes a sistergroup relationship of Annelida and Arthropoda.
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Affiliation(s)
- Georg Mayer
- Department of Anatomy and Cell Biology, University of Melbourne, Victoria 3010, Australia
| | - Steffen Harzsch
- Department of Evolutionary Neuroethology, Max-Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, D-07745 Jena, Germany
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Edgecombe GD, Giribet G. Evolutionary biology of centipedes (Myriapoda: Chilopoda). ANNUAL REVIEW OF ENTOMOLOGY 2007; 52:151-70. [PMID: 16872257 DOI: 10.1146/annurev.ento.52.110405.091326] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
New insights into the anatomy, systematics, and biogeography of centipedes have put these predatory terrestrial arthropods at the forefront of evolutionary studies. Centipedes have also played a pivotal role in understanding high-level arthropod relationships. Their deep evolutionary history, with a fossil record spanning 420 million years, explains their current worldwide distribution. Recent analyses of combined morphological and molecular data provide a stable phylogeny that underpins evolutionary interpretations of their biology. The centipede trunk, with its first pair of legs modified into a venom-delivering organ followed by 15 to 191 leg pairs, is a focus of arthropod segmentation studies. Gene expression studies and phylogenetics shed light on key questions in evolutionary developmental biology concerning the often group-specific fixed number of trunk segments, how some centipedes add segments after hatching whereas others hatch with the complete segment count, the addition of segments through evolution, and the invariably odd number of leg-bearing trunk segments.
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Santhoshi S, Sugumar V, Munuswamy N. Localization of Serotonin Neuropiles in the Brain and Thoracic Ganglia of the Indian White Shrimp,Fenneropenaeus indicus: Phylogenetic Comparisons and Implications for Arthropod Relationships. Microsc Res Tech 2007. [DOI: 10.1002/jemt.20468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Katz PS. Evolution and development of neural circuits in invertebrates. Curr Opin Neurobiol 2006; 17:59-64. [PMID: 17174546 DOI: 10.1016/j.conb.2006.12.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 12/07/2006] [Indexed: 01/06/2023]
Abstract
Developmental mechanisms can shed light on how evolutionary diversity has arisen. Invertebrate nervous systems offer a wealth of diverse structures and functions from which to relate development to evolution. Individual homologous neurons have been shown to have distinct roles in species with different behaviors. In addition, specific neurons have been lost or gained in some phylogenetic lineages. The ability to address the neural basis of behavior at the cellular level in invertebrates has facilitated discoveries showing that species-specific behavior can arise from differences in synaptic strength, in neuronal structure and in neuromodulation. The mechanisms involved in the development of neural circuits lead to these differences across species.
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Affiliation(s)
- Paul S Katz
- Department of Biology, Georgia State University, PO Box 4010, Atlanta, GA 30302-4010, USA.
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Newcomb JM, Fickbohm DJ, Katz PS. Comparative mapping of serotonin-immunoreactive neurons in the central nervous systems of nudibranch molluscs. J Comp Neurol 2006; 499:485-505. [PMID: 16998939 DOI: 10.1002/cne.21111] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The serotonergic systems in nudibranch molluscs were compared by mapping the locations of serotonin-immunoreactive (5-HT-ir) neurons in 11 species representing all four suborders of the nudibranch clade: Dendronotoidea (Tritonia diomedea, Tochuina tetraquetra, Dendronotus iris, Dendronotus frondosus, and Melibe leonina), Aeolidoidea (Hermissenda crassicornis and Flabellina trophina), Arminoidea (Dirona albolineata, Janolus fuscus, and Armina californica), and Doridoidea (Triopha catalinae). A nomenclature is proposed to standardize reports of cell location in species with differing brain morphologies. Certain patterns of 5-HT immunoreactivity were found to be consistent for all species, such as the presence of 5-HT-ir neurons in the pedal and cerebral ganglia. Also, particular clusters of 5-HT-ir neurons in the anterior and posterior regions of the dorsal surface of the cerebral ganglion were always present. However, there were interspecies differences in the number of 5-HT-ir neurons in each cluster, and some clusters even exhibited strong intraspecies variability that was only weakly correlated with brain size. Phylogenetic analysis suggests that the presence of particular classes of 5-HT-ir neurons exhibits a great deal of homoplasy. The conserved features of the nudibranch serotonergic system presumably represent the shared ancestral structure, whereas the derived characters suggest substantial independent evolutionary changes in the number and presence of serotonergic neurons. Although a number of studies have demonstrated phylogenetic variability of peptidergic systems, this study suggests that serotonergic systems may also exhibit a high degree of homoplasy in some groups of organisms.
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Affiliation(s)
- James M Newcomb
- Department of Biology, Georgia State University, Atlanta, Georgia 30303, USA.
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Harzsch S, Vilpoux K, Blackburn DC, Platchetzki D, Brown NL, Melzer R, Kempler KE, Battelle BA. Evolution of arthropod visual systems: Development of the eyes and central visual pathways in the horseshoe crab Limulus polyphemus Linnaeus, 1758 (Chelicerata, Xiphosura). Dev Dyn 2006; 235:2641-55. [PMID: 16788994 DOI: 10.1002/dvdy.20866] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Despite ongoing interest into the architecture, biochemistry, and physiology of the visual systems of the xiphosuran Limulus polyphemus, their ontogenetic aspects have received little attention. Thus, we explored the development of the lateral eyes and associated neuropils in late embryos and larvae of these animals. The first external evidence of the lateral eyes was the appearance of white pigment spots-guanophores associated with the rudimentary photoreceptors-on the dorsolateral side of the late embryos, suggesting that these embryos can perceive light. The first brown pigment emerges in the eyes during the last (third) embryonic molt to the trilobite stage. However, ommatidia develop from this field of pigment toward the end of the larval trilobite stage so that the young larvae at hatching do not have object recognition. Double staining with the proliferation marker bromodeoxyuridine (BrdU) and an antibody against L. polyphemus myosin III, which is concentrated in photoreceptors of this species, confirmed previous reports that, in the trilobite larvae, new cellular material is added to the eye field from an anteriorly located proliferation zone. Pulse-chase experiments indicated that these new cells differentiate into new ommatidia. Examining larval eyes labeled for opsin showed that the new ommatidia become organized into irregular rows that give the eye field a triangular appearance. Within the eye field, the ommatidia are arranged in an imperfect hexagonal array. Myosin III immunoreactivity in trilobite larvae also revealed the architecture of the central visual pathways associated with the median eye complex and the lateral eyes. Double labeling with myosin III and BrdU showed that neurogenesis persists in the larval brain and suggested that new neurons of both the lamina and the medulla originate from a single common proliferation zone. These data are compared with eye development in Drosophila melanogaster and are discussed with regard to new ideas on eye evolution in the Euarthropoda.
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Affiliation(s)
- Steffen Harzsch
- Universität Ulm, Fakultät für Naturwissenschaften, Abteilung Neurobiologie, Ulm, Germany.
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Vilpoux K, Sandeman R, Harzsch S. Early embryonic development of the central nervous system in the Australian crayfish and the Marbled crayfish (Marmorkrebs). Dev Genes Evol 2006; 216:209-23. [PMID: 16479399 DOI: 10.1007/s00427-005-0055-2] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Accepted: 12/06/2005] [Indexed: 10/25/2022]
Abstract
This study sets out to provide a systematic analysis of the development of the primordial central nervous system (CNS) in embryos of two decapod crustaceans, the Australian crayfish Cherax destructor (Malacostraca, Decapoda, Astacida) and the parthenogenetic Marbled crayfish (Marmorkrebs, Malacostraca, Decapoda, Astacida) by histochemical labelling with phalloidin, a general marker for actin. One goal of our study was to examine the neurogenesis in these two organisms with a higher temporal resolution than previous studies did. The second goal was to explore if there are any developmental differences between the parthenogenetic Marmorkrebs and the sexually reproducing Australian crayfish. We found that in the embryos of both species the sequence of neurogenetic events and the architecture of the embryonic CNS are identical. The naupliar neuromeres proto-, deuto-, tritocerebrum, and the mandibular neuromeres emerge simultaneously. After this "naupliar brain" has formed, there is a certain time lag before the maxilla one primordium develops and before the more caudal neuromeres follow sequentially in the characteristic anterior-posterior gradient. Because the malacostracan egg-nauplius represents a re-capitulation of a conserved ancestral information, which is expressed during development, we speculate that the naupliar brain also conserves an ancestral piece of information on how the brain architecture of an early crustacean or even arthropod ancestor may have looked like. Furthermore, we compare the architecture of the embryonic crayfish CNS to that of the brain and thoracic neuromeres in insects and discuss the similarities and differences that we found against an evolutionary background.
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Affiliation(s)
- K Vilpoux
- Fakultät für Naturwissenschaften, Abteilung Neurobiologie und Sektion Biosystematische Dokumentation, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Origin and differentiation of nephridia in the Onychophora provide no support for the Articulata. ZOOMORPHOLOGY 2005. [DOI: 10.1007/s00435-005-0006-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Harzsch S, Müller CHG, Wolf H. From variable to constant cell numbers: cellular characteristics of the arthropod nervous system argue against a sister-group relationship of Chelicerata and "Myriapoda" but favour the Mandibulata concept. Dev Genes Evol 2004; 215:53-68. [PMID: 15592874 DOI: 10.1007/s00427-004-0451-z] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2004] [Accepted: 11/05/2004] [Indexed: 11/25/2022]
Abstract
In the new debate on arthropod phylogeny, structure and development of the nervous system provide important arguments. The architecture of the brain of Hexapoda, Crustacea and Chelicerata in recent years has been thoroughly compared against an evolutionary background. However, comparative aspects of the nervous systems in these taxa at the cellular level have been examined in only a few studies. This review sets out to summarize these aspects and to analyse the existing data with respect to the concept of individually identifiable neurons. In particular, mechanisms of neurogenesis, the morphology of serotonergic interneurons, the number of motoneurons, and cellular features and development of the lateral eyes are discussed. We conclude that in comparison to the Mandibulata, in Chelicerata the numbers of neurons in the different classes examined are much higher and in many cases are not fixed but variable. The cell numbers in Mandibulata are lower and the majority of neurons are individually identifiable. The characters explored in this review are mapped onto an existing phylogram, as derived from brain architecture in which the Hexapoda are an in-group of the Crustacea, and there is not any conflict of the current data with such a phylogenetic position of the Hexapoda. Nevertheless, these characters argue against a sister-group relationship of "Myriapoda" and Chelicerata as has been recently suggested in several molecular studies, but instead provide strong evidence in favour of the Mandibulata concept.
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Affiliation(s)
- Steffen Harzsch
- Sektion Biosystematische Dokumentation und Abteilung Neurobiologie, Fakultät für Naturwissenschaften, Universität Ulm, Albert-Einstein-Strasse 11, 89081, Ulm, Germany.
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Fanenbruck M, Harzsch S, Wägele JW. The brain of the Remipedia (Crustacea) and an alternative hypothesis on their phylogenetic relationships. Proc Natl Acad Sci U S A 2004; 101:3868-73. [PMID: 15004272 PMCID: PMC374336 DOI: 10.1073/pnas.0306212101] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Remipedia are rare and ancient mandibulate arthropods inhabiting almost inaccessible submerged cave systems. Their phylogenetic position is still enigmatic and the subject of extremely controversial debates. To contribute arguments to this discussion, we analyzed the brain of Godzilliognomus frondosus Yager, 1989 (Remipedia, Godzilliidae) and provide a detailed 3D reconstruction of its anatomy. This reconstruction yielded the surprising finding that in comparison with the brain of other crustaceans such as representatives of the Branchiopoda and Maxillopoda the brain of G. frondosus is highly organized and well differentiated. It is matched in complexity only by the brain of "higher" crustaceans (Malacostraca) and Hexapoda. A phylogenetic analysis limited to brain anatomy across the Mandibulata strongly contradicts the prevailing hypothesis that the Remipedia are a basal, ancestral crustacean group but instead argues in favor of a remipede-malacostracan-hexapod clade and most likely a sister-group relationship of Remipedia and Malacostraca.
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Affiliation(s)
- Martin Fanenbruck
- Fakultät Biologie, Ruhr-Universität Bochum, Lehrstuhl für Spezielle Zoologie, 44780 Bochum, Germany
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