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von Döhren J. Comparative development of the serotonin- and FMRFamide-immunoreactive components of the nervous system in two distantly related ribbon worm species (Nemertea, Spiralia). Front Neurosci 2024; 18:1375208. [PMID: 38586190 PMCID: PMC10998470 DOI: 10.3389/fnins.2024.1375208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 03/04/2024] [Indexed: 04/09/2024] Open
Abstract
Introduction Neurodevelopment in larval stages of non-model organisms, with a focus on the serotonin- and FMRFamide-immunoreactive components, has been in the focus of research in the recent past. However, some taxonomic groups remain understudied. Nemertea (ribbon worms) represent such an understudied clade with only few reports on nervous system development mostly from phylogenetically or developmentally derived species. It would be insightful to explore neurodevelopment in additional species to be able to document the diversity and deduce common patterns to trace the evolution of nervous system development. Methods Fluorescent immunohistochemical labeling with polyclonal primary antibodies against serotonin and FMRF-amide and a monoclonal antibody against synapsin performed on series of fixed larval stages of two nemertean species Cephalothrix rufifrons (Archinemertea, Palaeonemertea) and Emplectonema gracile (Monostilifera, Hoplonemertea) were analyzed with confocal laser scanning microscopy. Results This contribution gives detailed accounts on the development of the serotonin- and FMRFamide-immunoreactive subsets of the nervous system in two nemertean species from the first appearance of the respective signals. Additionally, data on synapsin-like immunoreactivity illustrates the general structure of neuropil components. Events common to both investigated species are the appearance of serotonin-like immunoreactive signals before the appearance of FMRF-like immunoreactive signals and the strict progression of the development of the lateral nerve cords from the anteriorly located, ring-shaped brain toward the posterior pole of the larva. Notable differences are (1) the proboscis nervous system that is developing much earlier in investigated larval stages of E. gracile and (2) distinct early, but apparently transient, serotonergic neurons on the frontal and caudal pole of the larva in E. gracile that seem to be absent in C. rufifrons. Discussion According to the results from this investigation and in line with previously published accounts on nervous system development, the hypothetical last common ancestor of Nemertea had a ring-shaped brain arranged around the proboscis opening, from which a pair of ventro-lateral nerve cords develops in anterior to posterior progression. Early frontal and caudal serotonergic neurons that later degenerate or cease to express serotonin are an ancestral character of Nemertea that they share with several other spiralian clades.
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Affiliation(s)
- Jörn von Döhren
- Bonn Institute of Organismic Biology (BIOB), Animal Biodiversity Section, University of Bonn, Bonn, Germany
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Worsaae K, Rouan A, Seaver E, Miyamoto N, Tilic E. Postembryonic development and male paedomorphosis in Osedax (Siboglinidae, Annelida). Front Neurosci 2024; 18:1369274. [PMID: 38562300 PMCID: PMC10984269 DOI: 10.3389/fnins.2024.1369274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 01/31/2024] [Indexed: 04/04/2024] Open
Abstract
Most species of the bone-devouring marine annelid, Osedax, display distinct sexual dimorphism with macroscopic sedentary females rooted in bones and free-living microscopic dwarf males. The paedomorphic male resembles the non-feeding metatrochophore larva in size, presence of eight pairs of chaetae, and a head ciliation potentially representing a residual prototroch. The male development may thus uniquely reiterate and validate the theoretical heterochrony process "progenesis", which suggests that an accelerated sexual maturation and early arrest of somatic growth can lead to a miniaturized and paedomorphic adult. In this study, we describe the postembryonic larval and juvenile organogenesis of Osedax japonicus to test for a potential synchronous arrest of somatic growth during male development. Five postembryonic stages could be distinguished, resembling day one to five in the larval development at 10°C: (0D) first cleavage of fertilized eggs (embryos undergo unequal spiral cleavage), (1D) pre-trochophore, with apical organ, (2D) early trochophore, + prototroch, brain, circumesophageal connectives and subesophageal commissure, (3D) trochophore, + telotroch, four ventral nerves, (4D) early metatrochophore, + protonephridia, dorsal and terminal sensory organs, (5D) metatrochophore, + two ventral paratrochs, mid-ventral nerve, posterior trunk commissure, two dorsal nerves; competent for metamorphosis. The larval development largely mirrors that of other lecithotrophic annelid larvae but does not show continuous chaetogenesis or full gut development. Additionally, O. japonicus larvae exhibit an unpaired, mid-dorsal, sensory organ. Female individuals shed their larval traits during metamorphosis and continue organogenesis (including circulatory system) and extensive growth for 2-3 weeks before developing oocytes. In contrast, males develop sperm within a day of metamorphosis and display a synchronous metamorphic arrest in neural and muscular development, retaining a large portion of larval features post metamorphosis. Our findings hereby substantiate male miniaturization in Osedax to be the outcome of an early and synchronous offset of somatic development, fitting the theoretical process "progenesis". This may be the first compelling morpho-developmental exemplification of a progenetic origin of a microscopic body plan. The presented morphological staging system will further serve as a framework for future examination of molecular patterns and pathways determining Osedax development.
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Affiliation(s)
- Katrine Worsaae
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Alice Rouan
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Elaine Seaver
- The Whitney Laboratory for Marine Bioscience, University of Florida, Gainesville, FL, United States
| | - Norio Miyamoto
- X-STAR, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Ekin Tilic
- Marine Biological Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Department of Marine Zoology, Senckenberg Research Institute and Natural History Museum, Frankfurt, Germany
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Shunkina KV, Starunova ZI, Novikova EL, Starunov VV. Mass Start or Time Trial? Structure of the Nervous System and Neuroregeneration in Pygospio elegans (Spionidae, Annelida). BIOLOGY 2023; 12:1412. [PMID: 37998011 PMCID: PMC10669057 DOI: 10.3390/biology12111412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 10/30/2023] [Accepted: 11/07/2023] [Indexed: 11/25/2023]
Abstract
The spionid worm Pygospio elegans is a convenient model for regeneration studies due to its accessibility, high tolerance, and ease of maintenance in laboratory culture. This article presents the findings regarding neuroregeneration and the structure of the nervous system based on antibody labeling of serotonin and FMRFamide. We propose the main stages of central nervous system neurogenesis during regeneration: single nerve fibers, a loop structure, and neurons in the brain and segmental ganglia. Nerve fibers and receptor cells of the peripheral nerve system can be traced to different stages of regeneration. We also provide a comparison of our results with previous data on the structure and regeneration of the nervous system based on antibody labeling of catecholamines, gamma-aminobutyric acid, and histamine and with the results for other annelids.
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Affiliation(s)
| | | | - Elena L. Novikova
- Zoological Institute RAS, Saint Petersburg 199034, Russia; (K.V.S.)
- Faculty of Biology, St. Petersburg State University, Saint Petersburg 199034, Russia
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Starunova ZI, Shunkina KV, Novikova EL, Starunov VV. Histamine and gamma-aminobutyric acid in the nervous system of Pygospio elegans (Annelida: Spionidae): structure and recovery during reparative regeneration. BMC ZOOL 2022; 7:58. [PMID: 37170300 PMCID: PMC10127018 DOI: 10.1186/s40850-022-00160-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 11/18/2022] [Indexed: 12/12/2022] Open
Abstract
Abstract
Background
In recent two decades, studies of the annelid nervous systems were revolutionized by modern cell labeling techniques and state-of-the-art microscopy techniques. However, there are still huge gaps in our knowledge on the organization and functioning of their nervous system. Most of the recent studies have focused on the distribution of serotonin and FMRFamide, while the data about many other basic neurotransmitters such as histamine (HA) and gamma-aminobutyric acid (GABA) are scarce.
Results
Using immunohistochemistry and confocal microscopy we studied the distribution of histamine and gamma-aminobutyric acid in the nervous system of a spionid annelid Pygospio elegans and traced their redevelopment during reparative regeneration. Both neurotransmitters show specific patterns in central and peripheral nervous systems. HA-positive cells are concentrated mostly in the brain, while GABA-positive cell somata contribute equally to brain and segmental ganglia. Some immunoreactive elements were found in peripheral nerves. Both substances were revealed in high numbers in bipolar sensory cells in the palps. The first signs of regenerating HAergic and GABAergic systems were detected only by 3 days after the amputation. Further redevelopment of GABAergic system proceeds faster than that of HAergic one.
Conclusions
Comparisons with other annelids and mollusks examined in this respect revealed a number of general similarities in distribution patterns of HAergic and GABAergic cells in different species. Overall, the differences in the full redevelopment of various neurotransmitters correlate with neuronal development during embryogenesis. Our results highlight the importance of investigating the distribution of different neurotransmitters in comparative morphological and developmental studies.
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Fofanova E, Mayorova TD, Voronezhskaya EE. Dinophiliformia early neurogenesis suggests the evolution of conservative neural structures across the Annelida phylogenetic tree. PeerJ 2021; 9:e12386. [PMID: 34966573 PMCID: PMC8667735 DOI: 10.7717/peerj.12386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 10/04/2021] [Indexed: 11/27/2022] Open
Abstract
Despite the increasing data concerning the structure of the adult nervous system in various Lophotrochozoa groups, the early events during the neurogenesis of rare and unique groups need clarification. Annelida are a diverse clade of Lophotrochozoa, and their representatives demonstrate a variety of body plans, lifestyles, and life cycles. Comparative data about the early development are available for Errantia, Sedentaria, Sipuncula, and Palaeoannelida; however, our knowledge of Dinophiliformia is currently scarce. Representatives of Dinophiliformia are small interstitial worms combining unique morphological features of different Lophotrochozoan taxa and expressing paedomorphic traits. We describe in detail the early neurogenesis of two related species: Dimorphilus gyrociliatus and Dinophilus vorticoides, from the appearance of first nerve cells until the formation of an adult body plan. In both species, the first cells were detected at the anterior and posterior regions at the early trochophore stage and demonstrated positive reactions with pan-neuronal marker anti-acetylated tubulin only. Long fibers of early cells grow towards each other and form longitudinal bundles along which differentiating neurons later appear and send their processes. We propose that these early cells serve as pioneer neurons, forming a layout of the adult nervous system. The early anterior cell of D. vorticoides is transient and present during the short embryonic period, while early anterior and posterior cells in D. gyrociliatus are maintained throughout the whole lifespan of the species. During development, the growing processes of early cells form compact brain neuropile, paired ventral and lateral longitudinal bundles; unpaired medial longitudinal bundle; and commissures in the ventral hyposphere. Specific 5-HT- and FMRFa-immunopositive neurons differentiate adjacent to the ventral bundles and brain neuropile in the middle trochophore and late trochophore stages, i.e. after the main structures of the nervous system have already been established. Processes of 5-HT- and FMRFa-positive cells constitute a small proportion of the tubulin-immunopositive brain neuropile, ventral cords, and commissures in all developmental stages. No 5-HT- and FMRFa-positive cells similar to apical sensory cells of other Lophotrochozoa were detected. We conclude that: (i) like in Errantia and Sedentaria, Dinophiliformia neurogenesis starts from the peripheral cells, whose processes prefigure the forming adult nervous system, (ii) Dinophiliformia early cells are negative to 5-HT and FMRFa antibodies like Sedentaria pioneer cells.
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Affiliation(s)
- Elizaveta Fofanova
- Department of Comparative and Developmental Physiology, Koltzov Institute of Developmental Biology RAS, Moscow, Russia
| | - Tatiana D Mayorova
- Department of Comparative and Developmental Physiology, Koltzov Institute of Developmental Biology RAS, Moscow, Russia.,Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland, USA
| | - Elena E Voronezhskaya
- Department of Comparative and Developmental Physiology, Koltzov Institute of Developmental Biology RAS, Moscow, Russia
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Carrillo-Baltodano AM, Seudre O, Guynes K, Martín-Durán JM. Early embryogenesis and organogenesis in the annelid Owenia fusiformis. EvoDevo 2021; 12:5. [PMID: 33971947 PMCID: PMC8111721 DOI: 10.1186/s13227-021-00176-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 04/23/2021] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Annelids are a diverse group of segmented worms within Spiralia, whose embryos exhibit spiral cleavage and a variety of larval forms. While most modern embryological studies focus on species with unequal spiral cleavage nested in Pleistoannelida (Sedentaria + Errantia), a few recent studies looked into Owenia fusiformis, a member of the sister group to all remaining annelids and thus a key lineage to understand annelid and spiralian evolution and development. However, the timing of early cleavage and detailed morphogenetic events leading to the formation of the idiosyncratic mitraria larva of O. fusiformis remain largely unexplored. RESULTS Owenia fusiformis undergoes equal spiral cleavage where the first quartet of animal micromeres are slightly larger than the vegetal macromeres. Cleavage results in a coeloblastula approximately 5 h post-fertilization (hpf) at 19 °C. Gastrulation occurs via invagination and completes 4 h later, with putative mesodermal precursors and the chaetoblasts appearing 10 hpf at the dorso-posterior side. Soon after, at 11 hpf, the apical tuft emerges, followed by the first neurons (as revealed by the expression of elav1 and synaptotagmin-1) in the apical organ and the prototroch by 13 hpf. Muscles connecting the chaetal sac to various larval tissues develop around 18 hpf and by the time the mitraria is fully formed at 22 hpf, there are FMRFamide+ neurons in the apical organ and prototroch, the latter forming a prototrochal ring. As the mitraria feeds, it grows in size and the prototroch expands through active proliferation. The larva becomes competent after ~ 3 weeks post-fertilization at 15 °C, when a conspicuous juvenile rudiment has formed ventrally. CONCLUSIONS Owenia fusiformis embryogenesis is similar to that of other equal spiral cleaving annelids, supporting that equal cleavage is associated with the formation of a coeloblastula, gastrulation via invagination, and a feeding trochophore-like larva in Annelida. The nervous system of the mitraria larva forms earlier and is more elaborated than previously recognized and develops from anterior to posterior, which is likely an ancestral condition to Annelida. Altogether, our study identifies the major developmental events during O. fusiformis ontogeny, defining a conceptual framework for future investigations.
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Affiliation(s)
| | - Océane Seudre
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Kero Guynes
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - José María Martín-Durán
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
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Hou X, Qin Z, Wei M, Fu Z, Liu R, Lu L, Bai S, Ma Y, Zhang Z. Identification of the neuropeptide precursor genes potentially involved in the larval settlement in the Echiuran worm Urechis unicinctus. BMC Genomics 2020; 21:892. [PMID: 33317448 PMCID: PMC7737342 DOI: 10.1186/s12864-020-07312-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 12/07/2020] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND In marine invertebrate life cycles, which often consist of planktonic larval and benthonic adult stages, settlement of the free-swimming larva to the sea floor in response to environmental cues is a key life cycle transition. Settlement is regulated by a specialized sensory-neurosecretory system, the larval apical organ. The neuroendocrine mechanisms through which the apical organ transduces environmental cues into behavioral responses during settlement are not fully understood yet. RESULTS In this study, a total of 54 neuropeptide precursors (pNPs) were identified in the Urechis unicinctus larva and adult transcriptome databases using local BLAST and NpSearch prediction, of which 10 pNPs belonging to the ancient eumetazoa, 24 pNPs belonging to the ancient bilaterian, 3 pNPs belonging to the ancient protostome, 9 pNPs exclusive in lophotrochozoa, 3 pNPs exclusive in annelid, and 5 pNPs only found in U. unicinctus. Furthermore, four pNPs (MIP, FRWamide, FxFamide and FILamide) which may be associated with the settlement and metamorphosis of U. unicinctus larvae were analysed by qRT-PCR. Whole-mount in situ hybridization results showed that all the four pNPs were expressed in the region of the apical organ of the larva, and the positive signals were also detected in the ciliary band and abdomen chaetae. We speculated that these pNPs may regulate the movement of larval cilia and chaeta by sensing external attachment signals. CONCLUSIONS This study represents the first comprehensive identification of neuropeptides in Echiura, and would contribute to a complete understanding on the roles of various neuropeptides in larval settlement of most marine benthonic invertebrates.
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Affiliation(s)
- Xitan Hou
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Zhenkui Qin
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Maokai Wei
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Zhong Fu
- Hebei Research Institute of Marine and Fishery Science, Qinhuangdao, 066002, China
| | - Ruonan Liu
- College of Medical Engineering, Jining Medical University, Jining, 272067, China
| | - Li Lu
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Shumiao Bai
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Yubin Ma
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China.
| | - Zhifeng Zhang
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China. .,Laboratory of Tropical Marine Germplasm Resources and Breeding Engineering, Sanya Oceanographic Institution, Ocean University of China, Sanya, 572000, China.
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Kumar S, Tumu SC, Helm C, Hausen H. The development of early pioneer neurons in the annelid Malacoceros fuliginosus. BMC Evol Biol 2020; 20:117. [PMID: 32928118 PMCID: PMC7489019 DOI: 10.1186/s12862-020-01680-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 08/27/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Nervous system development is an interplay of many processes: the formation of individual neurons, which depends on whole-body and local patterning processes, and the coordinated growth of neurites and synapse formation. While knowledge of neural patterning in several animal groups is increasing, data on pioneer neurons that create the early axonal scaffold are scarce. Here we studied the first steps of nervous system development in the annelid Malacoceros fuliginosus. RESULTS We performed a dense expression profiling of a broad set of neural genes. We found that SoxB expression begins at 4 h postfertilization, and shortly later, the neuronal progenitors can be identified at the anterior and the posterior pole by the transient and dynamic expression of proneural genes. At 9 hpf, the first neuronal cells start differentiating, and we provide a detailed description of axonal outgrowth of the pioneer neurons that create the primary neuronal scaffold. Tracing back the clonal origin of the ventral nerve cord pioneer neuron revealed that it is a descendant of the blastomere 2d (2d221), which after 7 cleavages starts expressing Neurogenin, Acheate-Scute and NeuroD. CONCLUSIONS We propose that an anterior and posterior origin of the nervous system is ancestral in annelids. We suggest that closer examination of the first pioneer neurons will be valuable in better understanding of nervous system development in spirally cleaving animals, to determine the potential role of cell-intrinsic properties in neuronal specification and to resolve the evolution of nervous systems.
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Affiliation(s)
- Suman Kumar
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Sharat Chandra Tumu
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Conrad Helm
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.,Present Address: Johann-Friedrich-Blumenbach Institute for Zoology and Anthropology, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.
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Yurchenko OV, Savelieva AV, Kolotuchina NK, Voronezhskaya EE, Dyachuk VA. Peripheral sensory neurons govern development of the nervous system in bivalve larvae. EvoDevo 2019; 10:22. [PMID: 31528326 PMCID: PMC6743156 DOI: 10.1186/s13227-019-0133-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 08/21/2019] [Indexed: 12/15/2022] Open
Abstract
Recent findings regarding early lophotrochozoan development have altered the conventional model of neurogenesis and revealed that peripheral sensory elements play a key role in the initial organization of the larval nervous system. Here, we describe the main neurogenetic events in bivalve mollusks in comparison with other Lophotrochozoa, emphasizing a novel role for early neurons in establishing larval nervous systems and speculating about the morphogenetic function of the apical organ. We demonstrate that during bivalve development, peripheral sensory neurons utilizing various transmitters differentiate before the apical organ emerges. The first neurons and their neurites serve as a scaffold for the development of the nervous system. During veliger stage, cerebral, pleural, and visceral ganglia form along the lateral (visceral) nerve cords in anterior-to-posterior axis. The pedal ganglia and corresponding ventral (pedal) nerve cords develop much later, after larval settlement and metamorphosis. Pharmacological abolishment of the serotonin gradient within the larval body disrupts the navigation of "pioneer" axons resulting in malformation of the whole nervous system architecture. Comparative morphological data on neurogenetic events in bivalve mollusks shed new light on the origin of the nervous system, mechanisms of early axon navigation, and sequence of the tetraneurous nervous system formation. Furthermore, this information improves our understanding of the basic nervous system architecture in larval Bivalvia and Mollusca.
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Affiliation(s)
- Olga V. Yurchenko
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
| | - Anna V. Savelieva
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
| | - Natalia K. Kolotuchina
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
| | - Elena E. Voronezhskaya
- N.K. Koltsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 119991 Russia
| | - Vyacheslav A. Dyachuk
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Department of Nanophotonics and Metamaterials, ITMO University, St. Petersburg, Russia
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Rimskaya-Korsakova NN, Galkin SV, Malakhov VV. The neuroanatomy of the siboglinid Riftia pachyptila highlights sedentarian annelid nervous system evolution. PLoS One 2018; 13:e0198271. [PMID: 30543637 PMCID: PMC6292602 DOI: 10.1371/journal.pone.0198271] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 11/24/2018] [Indexed: 12/28/2022] Open
Abstract
Tracing the evolution of the siboglinid group, peculiar group of marine gutless annelids, requires the detailed study of the fragmentarily explored central nervous system of vestimentiferans and other siboglinids. 3D reconstructions of the neuroanatomy of Riftia revealed that the "brain" of adult vestimentiferans is a fusion product of the supraesophageal and subesophageal ganglia. The supraesophageal ganglion-like area contains the following neural structures that are homologous to the annelid elements: the peripheral perikarya of the brain lobes, two main transverse commissures, mushroom-like structures, commissural cell cluster, and the circumesophageal connectives with two roots which give rise to the palp neurites. Three pairs of giant perikarya are located in the supraesophageal ganglion, giving rise to the paired giant axons. The circumesophageal connectives run to the VNC. The subesophageal ganglion-like area contains a tripartite ventral aggregation of perikarya (= the postoral ganglion of the VNC) interconnected by the subenteral commissure. The paired VNC is intraepidermal, not ganglionated over most of its length, associated with the ciliary field, and comprises the giant axons. The pairs of VNC and the giant axons fuse posteriorly. Within siboglinids, the vestimentiferans are distinguished by a large and considerably differentiated brain. This reflects the derived development of the tentacle crown. The tentacles of vestimentiferans are homologous to the annelid palps based on their innervation from the dorsal and ventral roots of the circumesophageal connectives. Neuroanatomy of the vestimentiferan brains is close to the brains of Cirratuliiformia and Spionida/Sabellida, which have several transverse commissures, specific position of the giant somata (if any), and palp nerve roots (if any). The palps and palp neurite roots originally developed in all main annelid clades (basally branching, errantian and sedentarian annelids), show the greatest diversity in their number in sedentarian species. Over the course of evolution of Sedentaria, the number of palps and their nerve roots either dramatically increased (as in vestimentiferan siboglinids) or were lost.
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Affiliation(s)
| | - Sergey V. Galkin
- Laboratory of Ocean Benthic Fauna, Shirshov Institute of Oceanology of the Russian Academy of Science, Moscow, Russia
| | - Vladimir V. Malakhov
- Department of Invertebrate Zoology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
- Far Eastern Federal University, Vladivostok, Russia
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Battonyai I, Voronezhskaya EE, Obukhova A, Horváth R, Nezlin LP, Elekes K. Neuronal Development in the Larvae of the Invasive Biofouler Dreissena polymorpha (Mollusca: Bivalvia), with Special Attention to Sensory Elements and Swimming Behavior. THE BIOLOGICAL BULLETIN 2018; 234:192-206. [PMID: 29949436 DOI: 10.1086/698511] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Although understanding of the neuronal development of Trochozoa has progressed recently, little attention has been paid to freshwater bivalves, including species with a strong ecological impact, such as the zebra mussel (Dreissena polymorpha). Therefore, an important question might concern how the developing nervous system is involved in the formation of the rapid and successful invasive behavior of this species. Our aim was to reveal the neuronal development of trochophore and veliger larvae of Dreissena, with special attention to the organization of sensory structures and their possible involvement in detecting environmental cues. After applying serotonin and FMRFamide immunocytochemistry, the first serotonin immunoreactive sensory elements appeared 16-18 hours after fertilization, whereas the first FMRFamide immunoreactive sensory cell was seen only at 32 hours of development (trochophore stage). Later, sensory elements were found in three parts of the larval body, including the apical organ, the posterior region, and the stomach. Although differences in the timing of appearance and the morphology of cells were observed, the two signaling systems showed basic similarity in their organization pattern until the end of the veliger stage. Pharmacological, physiological, and quantitative immunocytochemical investigations were also performed, suggesting the involvement of both the serotoninergic system and the FMRFamidergic system in sensomotor processes. Manipulation of the serotonin synthesis by para-chloroplenylalanine and 5-hydroxytryptophane, as well as application of increased salinity, influenced larval swimming activity, both accompanied by changes in immunofluorescence intensity. We concluded that these two early sensory systems may play an important role in the development of settlement competency of this biofouling invasive bivalve, Dreissena.
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Key Words
- 5-HT, serotonin
- 5-HTP, 5-hydroxytryptophan
- AO, apical organ
- DAPI, 4ʹ,6-diamidino-2-phenylindole
- EDTA, ethylenediaminetetraacetic acid
- FMRFa, FMRFamide
- FW, filtered water
- IHC, immunohistochemical
- IR, immunoreactive
- PBS, phosphate-buffered saline
- PBS-TX-NGS, PBS containing 1% Triton X-100 and 10% normal goat serum
- PFA, paraformaldehyde;
- PN, posterior neuron.
- hpf, hours post-fertilization
- pCPA, para-chlorophenilalanine
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Yurchenko OV, Skiteva OI, Voronezhskaya EE, Dyachuk VA. Nervous system development in the Pacific oyster, Crassostrea gigas (Mollusca: Bivalvia). Front Zool 2018; 15:10. [PMID: 29681988 PMCID: PMC5896133 DOI: 10.1186/s12983-018-0259-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 03/20/2018] [Indexed: 01/26/2023] Open
Abstract
Background Bivalves comprise a large, highly diverse taxon of invertebrate species. Developmental studies of neurogenesis among species of Bivalvia are limited. Due to a lack of neurogenesis information, it is difficult to infer a ground pattern for Bivalvia. To provide more comprehensive morphogenetic data on bivalve molluscs and relationships among molluscan clades, we investigated neurogenesis in the Pacific oyster, Crassostrea gigas, from the appearance of the first sensory cells to the formation of the larval ganglionic nervous system by co-immunocytochemistry of the neuronal markers FMRFamide or 5-HT and vesicular acetylcholine transporter (VAChT). Results Neurogenesis begins with the emergence of the apical serotonin-immunoreactive (5-HT-ir) sensory cells and paired sensory posttrochal dorsal and ventral FMRFamide-immunoreactive (FMRFamide-ir) cells at the early trochophore stage. Later, at the early veliger stage, the apical organ (AO) includes 5-HT-ir, FMRFamide-ir, and VAChT-ir cells. At the same stage, VAChT-ir cells appear in the posterior region of larvae and send axons towards the AO. Thus, FMRFamide-ir neurites and VAChT-ir processes form scaffolds for longitudinal neurite bundles develop into the paired ventral nerve cords (VNC). Later-appearing axons from the AO/CG neurons join the neurite bundles comprising the VNC. All larval ganglia appear along the VNC as paired or fused (epiathroid) clusters in late veliger and pediveliger larvae. We observed the transformation of the AO into the cerebral ganglia, which abundantly innervated the velum, and the transformation of ventral neurons into the pedal ganglia, innervating the foot, gills, and anterior adductor muscle. The visceral ganglia appear last in the pediveliger oyster and innervate the visceral mass and posterior adductor of premetamorphic larvae. In addition, a local FMRFamide-ir network was detected in the digestive system of pediveliger larvae. We identified VAChT-ir nervous elements in oyster larvae, which have not been observed previously in molluscs. Finally, we performed a morphology-based comparative analysis of neuronal structures among bivalve, conchiferan, and aculiferan species. Conclusions We described the development of the nervous system during the larval development in Crassostrea gigas. These data greatly advance the currently limited understanding of neurodevelopment in bivalves and mollusks, which has hampered the generation of a ground pattern reconstruction of the last common ancestor of Mollusca. Our morphological data support phylogenomic data indicating a closer Bivalvia-Gastropoda sister group relationship than the Bivalvia-Scaphopoda (Diasoma) group relationship. Electronic supplementary material The online version of this article (10.1186/s12983-018-0259-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Olga V Yurchenko
- 1National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
| | - Olga I Skiteva
- 2Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Elena E Voronezhskaya
- 3N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 119991 Russia.,Department of Pathology, Cell biology and Biochemistry, Central Tuberculosis Research Institute, Moscow, Russian Federation
| | - Vyacheslav A Dyachuk
- 1National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia.,5Far Eastern Federal University, Vladivostok, 690950 Russia.,6Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Some details of muscles innervations by FMRF-like nerve elements in planarian Girardia tigrina. ZOOMORPHOLOGY 2017. [DOI: 10.1007/s00435-017-0392-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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14
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Starunov VV, Voronezhskaya EE, Nezlin LP. Development of the nervous system in Platynereis dumerilii (Nereididae, Annelida). Front Zool 2017; 14:27. [PMID: 28559917 PMCID: PMC5445494 DOI: 10.1186/s12983-017-0211-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 05/09/2017] [Indexed: 12/14/2022] Open
Abstract
Background The structure and development of the nervous system in Lophotrochozoa has long been recognized as one of the most important subjects for phylogenetic and evolutionary discussion. Many recent papers have presented comprehensive data on the structure and development of catecholaminergic, serotonergic and FMRFamidergic parts of the nervous system. However, relatively few papers contain detailed descriptions of the nervous system in Annelida, one of the largest taxa of Lophotrochozoa. The polychaete species Platynereis dumerilii has recently become one of the more popular model animals in evolutionary and developmental biology. The goal of the present study was to provide a detailed description of its neuronal development. The data obtained will contribute to a better understanding of the basic features of neuronal development in polychaetes. Results We have studied the development of the nervous system in P. dumerilii utilizing histo- and immunochemical labelling of catecholamines, serotonin, FMRFamide related peptides, and acetylated tubulin. The first neuron differentiates at the posterior extremity of the protrochophore, reacts to the antibodies against both serotonin and FMRFamide. Then its fibres run forwards along the ventral side. Soon, more neurons appear at the apical extreme, and their basal neurites form the basel structure of the developing brain (cerebral neuropil and circumesophageal connectives). Initial development of the nervous system starts in two rudiments: anterior and posterior. At the nectochaete stage, segmental ganglia start to differentiate in the anterior-to-posterior direction, and the first structures of the stomatogastric and peripheral nervous system appear. All connectives including the unpaired ventral cord develop from initially paired nerves. Conclusions We present a detailed description of Platynereis dumerilii neuronal development based on anti-acetylated tubulin, serotonin, and FMRFamide-like immunostaining as well as catecholamine histofluorescence. The development of the nervous system starts from peripheral pioneer neurons at both the posterior and anterior poles of the larva, and their neurites form a scaffold upon which the adult central nervous system develops. The anterior-to-posterior mode of the ventral ganglia development challenges the primary heteronomy concept. Comparison with the development of Mollusca reveals substantial similarities with early neuronal development in larval Solenogastres. Electronic supplementary material The online version of this article (doi:10.1186/s12983-017-0211-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Viktor V Starunov
- Department of Invertebrate Zoology, St-Petersburg State University, St-Petersburg, 199034 Russia.,Zoological Institute Rus, Acad. Sci, St-Petersburg, 199034 Russia
| | | | - Leonid P Nezlin
- Institute of Developmental Biology, Rus. Acad. Sci, Moscow, 119991 Russia
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Verasztó C, Ueda N, Bezares-Calderón LA, Panzera A, Williams EA, Shahidi R, Jékely G. Ciliomotor circuitry underlying whole-body coordination of ciliary activity in the Platynereis larva. eLife 2017; 6. [PMID: 28508746 PMCID: PMC5531833 DOI: 10.7554/elife.26000] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 05/14/2017] [Indexed: 01/23/2023] Open
Abstract
Ciliated surfaces harbouring synchronously beating cilia can generate fluid flow or drive locomotion. In ciliary swimmers, ciliary beating, arrests, and changes in beat frequency are often coordinated across extended or discontinuous surfaces. To understand how such coordination is achieved, we studied the ciliated larvae of Platynereis dumerilii, a marine annelid. Platynereis larvae have segmental multiciliated cells that regularly display spontaneous coordinated ciliary arrests. We used whole-body connectomics, activity imaging, transgenesis, and neuron ablation to characterize the ciliomotor circuitry. We identified cholinergic, serotonergic, and catecholaminergic ciliomotor neurons. The synchronous rhythmic activation of cholinergic cells drives the coordinated arrests of all cilia. The serotonergic cells are active when cilia are beating. Serotonin inhibits the cholinergic rhythm, and increases ciliary beat frequency. Based on their connectivity and alternating activity, the catecholaminergic cells may generate the rhythm. The ciliomotor circuitry thus constitutes a stop-and-go pacemaker system for the whole-body coordination of ciliary locomotion. DOI:http://dx.doi.org/10.7554/eLife.26000.001 The oceans contain a wide variety of microscopic organisms including bacteria, algae and animal larvae. Many of the microscopic animals that live in water use thousands of beating hair-like projections called cilia instead of muscles to swim around in the water. Understanding how these animals move will aid our understanding of how ocean processes, such as the daily migration of plankton to and from the surface of the water, are regulated. The larvae of a ragworm called Platynereis use cilia to move around. Like other animals, Platynereis has a nervous system containing neurons that form networks to control the body. It is possible that the nervous system is involved in coordinating the activity of the cilia to allow the larvae to manoeuvre in the water, but it was not clear how this could work. Here, Veraszto et al. investigated how Platynereis is able to swim. The experiments show that the larvae can coordinate their cilia so that they all stop beating at the same time and fold into to the body. Then the larvae can stimulate all of their cilia to resume beating. Veraszto et al. used a technique called electron microscopy to study how the nervous system connects to the cilia. This revealed that several giant neurons span the entire length of the larva and connect to cells that bear cilia. When these neurons were active, all the cilia in the body closed. When a different group of neurons in the larva was active, all of the cilia resumed beating. Together, these two groups of neurons were ultimately responsible for the swimming motions of the larvae. Together, the findings of Veraszto et al. show that a few neurons in the nervous system of the larvae provide a sophisticated system for controlling how the larvae swim around. This suggests that the microscopic animals found in marine environments are a lot more sophisticated than previously appreciated. A next challenge is to find out how the neurons that control cilia connect to the rest of the animal’s nervous system and how different cues influence when the larva swims or stops swimming. This would help us understand how the environment influences the distribution of animal larvae in the oceans and how this may change in the future. DOI:http://dx.doi.org/10.7554/eLife.26000.002
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Affiliation(s)
- Csaba Verasztó
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Nobuo Ueda
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | | | - Aurora Panzera
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | | | - Réza Shahidi
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Gáspár Jékely
- Max Planck Institute for Developmental Biology, Tübingen, Germany
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16
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Nezlin LP, Voronezhskaya EE. Early peripheral sensory neurons in the development of trochozoan animals. Russ J Dev Biol 2017. [DOI: 10.1134/s1062360417020060] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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17
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Helm C, Vöcking O, Kourtesis I, Hausen H. Owenia fusiformis - a basally branching annelid suitable for studying ancestral features of annelid neural development. BMC Evol Biol 2016; 16:129. [PMID: 27306767 PMCID: PMC4910202 DOI: 10.1186/s12862-016-0690-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 05/23/2016] [Indexed: 12/15/2022] Open
Abstract
Background Comparative investigations on bilaterian neurogenesis shed light on conserved developmental mechanisms across taxa. With respect to annelids, most studies focus on taxa deeply nested within the annelid tree, while investigations on early branching groups are almost lacking. According to recent phylogenomic data on annelid evolution Oweniidae represent one of the basally branching annelid clades. Oweniids are thought to exhibit several plesiomorphic characters, but are scarcely studied - a fact that might be caused by the unique morphology and unusual metamorphosis of the mitraria larva, which seems to be hardly comparable to other annelid larva. In our study, we compare the development of oweniid neuroarchitecture with that of other annelids aimed to figure out whether oweniids may represent suitable study subjects to unravel ancestral patterns of annelid neural development. Our study provides the first data on nervous system development in basally branching annelids. Results Based on histology, electron microscopy and immunohistochemical investigations we show that development and metamorphosis of the mitraria larva has many parallels to other annelids irrespective of the drastic changes in body shape during metamorphosis. Such significant changes ensuing metamorphosis are mainly from diminution of a huge larval blastocoel and not from major restructuring of body organization. The larval nervous system features a prominent apical organ formed by flask-shaped perikarya and circumesophageal connectives that interconnect the apical and trunk nervous systems, in addition to serially arranged clusters of perikarya showing 5-HT-LIR in the ventral nerve cord, and lateral nerves. Both 5-HT-LIR and FMRFamide-LIR are present in a distinct nerve ring underlying the equatorial ciliary band. The connections arising from these cells innervate the circumesophageal connectives as well as the larval brain via dorsal and ventral neurites. Notably, no distinct somata with 5-HT -LIR in the apical organ are detectable in the larval stages of Owenia. Most of the larval neural elements including parts of the apical organ are preserved during metamorphosis and contribute to the juvenile nervous system. Conclusions Our studies in Owenia fusiformis strongly support that early branching annelids are comparable to other annelids with regard to larval neuroanatomy and formation of the juvenile nervous system. Therefore, Owenia fusiformis turns out to be a valuable study subject for comparative investigations and unravelling ancestral processes in neural development in Annelida and Bilateria in general. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0690-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Conrad Helm
- Sars - International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt. 55, Bergen, N-5008, Norway.
| | - Oliver Vöcking
- Sars - International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt. 55, Bergen, N-5008, Norway
| | - Ioannis Kourtesis
- Sars - International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt. 55, Bergen, N-5008, Norway
| | - Harald Hausen
- Sars - International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt. 55, Bergen, N-5008, Norway
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Kristof A, de Oliveira AL, Kolbin KG, Wanninger A. Neuromuscular development in Patellogastropoda (Mollusca: Gastropoda) and its importance for reconstructing ancestral gastropod bodyplan features. J ZOOL SYST EVOL RES 2015; 54:22-39. [PMID: 26869747 PMCID: PMC4747121 DOI: 10.1111/jzs.12112] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Within Gastropoda, limpets (Patellogastropoda) are considered the most basal branching taxon and its representatives are thus crucial for research into evolutionary questions. Here, we describe the development of the neuromuscular system in Lottia cf. kogamogai. In trochophore larvae, first serotonin‐like immunoreactivity (lir) appears in the apical organ and in the prototroch nerve ring. The arrangement and number of serotonin‐lir cells in the apical organ (three flask‐shaped, two round cells) are strikingly similar to those in putatively derived gastropods. First, FMRFamide‐lir appears in veliger larvae in the Anlagen of the future adult nervous system including the cerebral and pedal ganglia. As in other gastropods, the larvae of this limpet show one main and one accessory retractor as well as a pedal retractor and a prototroch muscle ring. Of these, only the pedal retractor persists until after metamorphosis and is part of the adult shell musculature. We found a hitherto undescribed, paired muscle that inserts at the base of the foot and runs towards the base of the tentacles. An apical organ with flask‐shaped cells, one main and one accessory retractor muscle is commonly found among gastropod larvae and thus might have been part of the last common ancestor.
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Affiliation(s)
- Alen Kristof
- Department of Integrative Zoology, University of Vienna, Vienna Austria
| | | | - Konstantin G Kolbin
- Laboratory of Cell Differentiation, A.V. Zhirmunsky Institute for Marine Biology, Far East Branch of the Russian Academy of Sciences, Vladivostok Russian Federation
| | - Andreas Wanninger
- Department of Integrative Zoology, University of Vienna, Vienna Austria
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20
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Raikova OI, Meyer-Wachsmuth I, Jondelius U. The plastic nervous system of Nemertodermatida. ORG DIVERS EVOL 2015. [DOI: 10.1007/s13127-015-0248-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Meyer NP, Carrillo-Baltodano A, Moore RE, Seaver EC. Nervous system development in lecithotrophic larval and juvenile stages of the annelid Capitella teleta. Front Zool 2015; 12:15. [PMID: 26167198 PMCID: PMC4498530 DOI: 10.1186/s12983-015-0108-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 05/20/2015] [Indexed: 11/24/2022] Open
Abstract
Background Reconstructing the evolutionary history of nervous systems requires an understanding of their architecture and development across diverse taxa. The spiralians encompass diverse body plans and organ systems, and within the spiralians, annelids exhibit a variety of morphologies, life histories, feeding modes and associated nervous systems, making them an ideal group for studying evolution of nervous systems. Results We describe nervous system development in the annelid Capitella teleta (Blake JA, Grassle JP, Eckelbarger KJ. Capitella teleta, a new species designation for the opportunistic and experimental Capitella sp. I, with a review of the literature for confirmed records. Zoosymposia. 2009;2:25–53) using whole-mount in situ hybridization for a synaptotagmin 1 homolog, nuclear stains, and cross-reactive antibodies against acetylated α-tubulin, 5-HT and FMRFamide. Capitella teleta is member of the Sedentaria (Struck TH, Paul C, Hill N, Hartmann S, Hosel C, Kube M, et al. Phylogenomic analyses unravel annelid evolution. Nature. 2011;471:95–8) and has an indirectly-developing, lecithotrophic larva. The nervous system of C. teleta shares many features with other annelids, including a brain and a ladder-like ventral nerve cord with five connectives, reiterated commissures, and pairs of peripheral nerves. Development of the nervous system begins with the first neurons differentiating in the brain, and follows a temporal order from central to peripheral and from anterior to posterior. Similar to other annelids, neurons with serotonin-like-immunoreactivity (5HT-LIR) and FMRFamide-like-immunoreactivity (FMRF-LIR) are found throughout the brain and ventral nerve cord. A small number of larval-specific neurons and neurites are present, but are visible only after the central nervous system begins to form. These larval neurons are not visible after metamorphosis while the rest of the nervous system is largely unchanged in juveniles. Conclusions Most of the nervous system that forms during larvogenesis in C. teleta persists into the juvenile stage. The first neurons differentiate in the brain, which contrasts with the early formation of peripheral, larval-specific neurons found in some spiralian taxa with planktotrophic larvae. Our study provides a clear indication that certain shared features among annelids - e.g., five connectives in the ventral nerve cord - are only visible during larval stages in particular species, emphasizing the need to include developmental data in ancestral character state reconstructions. The data provided in this paper will serve as an important comparative reference for understanding evolution of nervous systems, and as a framework for future molecular studies of development. Electronic supplementary material The online version of this article (doi:10.1186/s12983-015-0108-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Néva P Meyer
- Biology Department, Clark University, 950 Main Street, Worcester, MA 01610 USA
| | | | - Richard E Moore
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, 1955 East-west Road, Honolulu, HI 96822 USA
| | - Elaine C Seaver
- Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Boulevard, Saint Augustine, FL 32080 USA
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Wanninger A. Morphology is dead – long live morphology! Integrating MorphoEvoDevo into molecular EvoDevo and phylogenomics. Front Ecol Evol 2015. [DOI: 10.3389/fevo.2015.00054] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Starunov VV, Dray N, Belikova EV, Kerner P, Vervoort M, Balavoine G. A metameric origin for the annelid pygidium? BMC Evol Biol 2015; 15:25. [PMID: 25880037 PMCID: PMC4357181 DOI: 10.1186/s12862-015-0299-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Accepted: 01/29/2015] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Segmented body organizations are widely represented in the animal kingdom. Whether the last common bilaterian ancestor was already segmented is intensely debated. Annelids display broad morphological diversity but many species are among the most homonomous metameric animals. The front end (prostomium) and tail piece (pygidium) of annelids are classically described as non-segmental. However, the pygidium structure and development remain poorly studied. RESULTS Using different methods of microscopy, immunolabelling and a number of molecular markers, we describe the neural and mesodermal structures of the pygidium of Platynereis dumerilii. We establish that the pygidium possesses a complicated nervous system with a nerve ring and a pair of sensory ganglia, a complex intrinsic musculature, a large terminal circular blood sinus and an unusual unpaired torus-shaped coelomic cavity. We also describe some earlier steps of pygidial development and pygidial structure of mature animals after epitokous transformation. CONCLUSIONS We describe a much more complex organization of the pygidium of P. dumerilii than previously suggested. Many of the characteristics are strikingly similar to those found in the trunk segments, opening the debate on whether the pygidium and trunk segments derive from the same ancestral metameric unit. We analyze these scenarios in the context of two classical theories on the origin of segmentation: the cyclomeric/archicoelomate concept and the colonial theory. Both theories provide possible explanations for the partial or complete homology of trunk segments and pygidium.
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Affiliation(s)
- Viktor V Starunov
- Department of Invertebrate Zoology, Saint-Petersburg State University/ Universitetskaya nab. 7/9, 199034, Saint-Petersburg, Russia.
- Zoological Institute RAS/ Universitetskaya nab. 1, 199034, Saint-Petersburg, Russia.
| | - Nicolas Dray
- Institut Jacques Monod, CNRS/Université Paris Diderot, 15 rue Hélène Brion, 75013, Paris, France.
| | - Elena V Belikova
- Department of Invertebrate Zoology, Saint-Petersburg State University/ Universitetskaya nab. 7/9, 199034, Saint-Petersburg, Russia.
| | - Pierre Kerner
- Institut Jacques Monod, CNRS/Université Paris Diderot, 15 rue Hélène Brion, 75013, Paris, France.
| | - Michel Vervoort
- Institut Jacques Monod, CNRS/Université Paris Diderot, 15 rue Hélène Brion, 75013, Paris, France.
- Institut Universitaire de France, Paris, France.
| | - Guillaume Balavoine
- Institut Jacques Monod, CNRS/Université Paris Diderot, 15 rue Hélène Brion, 75013, Paris, France.
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Redl E, Scherholz M, Todt C, Wollesen T, Wanninger A. Development of the nervous system in Solenogastres (Mollusca) reveals putative ancestral spiralian features. EvoDevo 2014; 5:48. [PMID: 25904999 PMCID: PMC4406162 DOI: 10.1186/2041-9139-5-48] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 12/02/2014] [Indexed: 11/14/2022] Open
Abstract
Background The Solenogastres (or Neomeniomorpha) are a taxon of aplacophoran molluscs with contentious phylogenetic placement. Since available developmental data on non-conchiferan (that is, aculiferan) molluscs mainly stem from polyplacophorans, data on aplacophorans are needed to clarify evolutionary questions concerning the morphological features of the last common ancestor (LCA) of the Aculifera and the entire Mollusca. We therefore investigated the development of the nervous system in two solenogasters, Wirenia argentea and Gymnomenia pellucida, using immunocytochemistry and electron microscopy. Results Nervous system formation starts simultaneously from the apical and abapical pole of the larva with the development of a few cells of the apical organ and a posterior neurogenic domain. A pair of neurite bundles grows out from both the neuropil of the apical organ and the posterior neurogenic domain. After their fusion in the region of the prototroch, which is innervated by an underlying serotonin-like immunoreactive (−LIR) plexus, the larva exhibits two longitudinal neurite bundles - the future lateral nerve cords. The apical organ in its fully developed state exhibits approximately 8 to 10 flask-shaped cells but no peripheral cells. The entire ventral nervous system, which includes a pair of longitudinal neurite bundles (the future ventral nerve cords) and a serotonin-LIR ventromedian nerve plexus, appears simultaneously and is established after the lateral nervous system. During metamorphosis the apical organ and the prototrochal nerve plexus are lost. Conclusions The development of the nervous system in early solenogaster larvae shows striking similarities to other spiralians, especially polychaetes, in exhibiting an apical organ with flask-shaped cells, a single pair of longitudinal neurite bundles, a serotonin-LIR innervation of the prototroch, and formation of these structures from an anterior and a posterior neurogenic domain. This provides evidence for an ancestral spiralian pattern of early nervous system development and a LCA of the Spiralia with a single pair of nerve cords. In later nervous system development, however, the annelids deviate from all other spiralians including solenogasters in forming a posterior growth zone, which initiates teloblastic growth. Since this mode of organogenesis is confined to annelids, we conclude that the LCA of both molluscs and spiralians was unsegmented.
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Affiliation(s)
- Emanuel Redl
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Maik Scherholz
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Christiane Todt
- The Natural History Collections, University of Bergen, University Museum, Allégaten 41, 5007 Bergen, Norway
| | - Tim Wollesen
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Andreas Wanninger
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
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Xu F, Wang X, Feng Y, Huang W, Wang W, Li L, Fang X, Que H, Zhang G. Identification of conserved and novel microRNAs in the Pacific oyster Crassostrea gigas by deep sequencing. PLoS One 2014; 9:e104371. [PMID: 25137038 PMCID: PMC4138081 DOI: 10.1371/journal.pone.0104371] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 07/12/2014] [Indexed: 12/15/2022] Open
Abstract
MicroRNAs (miRNAs) play important roles in regulatory processes in various organisms. To date many studies have been performed in the investigation of miRNAs of numerous bilaterians, but limited numbers of miRNAs have been identified in the few species belonging to the clade Lophotrochozoa. In the current study, deep sequencing was conducted to identify the miRNAs of Crassostrea gigas (Lophotrochozoa) at a genomic scale, using 21 libraries that included different developmental stages and adult organs. A total of 100 hairpin precursor loci were predicted to encode miRNAs. Of these, 19 precursors (pre-miRNA) were novel in the oyster. As many as 53 (53%) miRNAs were distributed in clusters and 49 (49%) precursors were intragenic, which suggests two important biogenetic sources of miRNAs. Different developmental stages were characterized with specific miRNA expression patterns that highlighted regulatory variation along a temporal axis. Conserved miRNAs were expressed universally throughout different stages and organs, whereas novel miRNAs tended to be more specific and may be related to the determination of the novel body plan. Furthermore, we developed an index named the miRNA profile age index (miRPAI) to integrate the evolutionary age and expression levels of miRNAs during a particular developmental stage. We found that the swimming stages were characterized by the youngest miRPAIs. Indeed, the large-scale expression of novel miRNAs indicated the importance of these stages during development, particularly from organogenetic and evolutionary perspectives. Some potentially important miRNAs were identified for further study through significant changes between expression patterns in different developmental events, such as metamorphosis. This study broadened the knowledge of miRNAs in animals and indicated the presence of sophisticated miRNA regulatory networks related to the biological processes in lophotrochozoans.
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Affiliation(s)
- Fei Xu
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Xiaotong Wang
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | | | - Wen Huang
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Wei Wang
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Li Li
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | | | - Huayong Que
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Guofan Zhang
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- * E-mail:
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Helm C, Stevenson PA, Rouse GW, Bleidorn C. Immunohistochemical investigations of Myzostoma cirriferum and Mesomyzostoma cf. katoi (Myzostomida, Annelida) with implications for the evolution of the myzostomid body plan. ZOOMORPHOLOGY 2014. [DOI: 10.1007/s00435-014-0221-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Marlow H, Tosches MA, Tomer R, Steinmetz PR, Lauri A, Larsson T, Arendt D. Larval body patterning and apical organs are conserved in animal evolution. BMC Biol 2014; 12:7. [PMID: 24476105 PMCID: PMC3939940 DOI: 10.1186/1741-7007-12-7] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 01/24/2014] [Indexed: 12/31/2022] Open
Abstract
Background Planktonic ciliated larvae are characteristic for the life cycle of marine invertebrates. Their most prominent feature is the apical organ harboring sensory cells and neurons of largely undetermined function. An elucidation of the relationships between various forms of primary larvae and apical organs is key to understanding the evolution of animal life cycles. These relationships have remained enigmatic due to the scarcity of comparative molecular data. Results To compare apical organs and larval body patterning, we have studied regionalization of the episphere, the upper hemisphere of the trochophore larva of the marine annelid Platynereis dumerilii. We examined the spatial distribution of transcription factors and of Wnt signaling components previously implicated in anterior neural development. Pharmacological activation of Wnt signaling with Gsk3β antagonists abolishes expression of apical markers, consistent with a repressive role of Wnt signaling in the specification of apical tissue. We refer to this Wnt-sensitive, six3- and foxq2-expressing part of the episphere as the ‘apical plate’. We also unraveled a molecular signature of the apical organ - devoid of six3 but expressing foxj, irx, nkx3 and hox - that is shared with other marine phyla including cnidarians. Finally, we characterized the cell types that form part of the apical organ by profiling by image registration, which allows parallel expression profiling of multiple cells. Besides the hox-expressing apical tuft cells, this revealed the presence of putative light- and mechanosensory as well as multiple peptidergic cell types that we compared to apical organ cell types of other animal phyla. Conclusions The similar formation of a six3+, foxq2+ apical plate, sensitive to Wnt activity and with an apical tuft in its six3-free center, is most parsimoniously explained by evolutionary conservation. We propose that a simple apical organ - comprising an apical tuft and a basal plexus innervated by sensory-neurosecretory apical plate cells - was present in the last common ancestors of cnidarians and bilaterians. One of its ancient functions would have been the control of metamorphosis. Various types of apical plate cells would then have subsequently been added to the apical organ in the divergent bilaterian lineages. Our findings support an ancient and common origin of primary ciliated larvae.
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Affiliation(s)
- Heather Marlow
- European Molecular Biology Laboratory, Development Biology Unit, EMBL Heidelberg, Meyerhofstraße 1, 69117 Heidelberg, Germany.
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Temereva EN, Tsitrin EB. Development and organization of the larval nervous system in Phoronopsis harmeri: new insights into phoronid phylogeny. Front Zool 2014; 11:3. [PMID: 24418063 PMCID: PMC3924620 DOI: 10.1186/1742-9994-11-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Accepted: 01/09/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The organization and development of the nervous system has traditionally been used as an important character for establishing the relationships among large groups of animals. According to this criterion, phoronids were initially regarded as deuterostomian but have more recently been regarded as protostomian. The resolving of this conflict requires detailed information from poorly investigated members of phoronids, such as Phoronopsis harmeri. RESULTS The serotonin-like immunoreactive part of the P. harmeri nervous system changes during larval development. These changes mostly concern the nervous system of the hood and correlate with the appearance of the median and two marginal neurite bundles, the frontal organ, and the sensory field. The apical organ has bilateral symmetry. The tentacular neurite bundle passes under the tentacles, contains several types of perikarya, and gives rise to intertentacular bundles, which branch in the tentacle base and penetrate into adjacent tentacles by two lateroabfrontal bundles. There are two groups of dorsolateral perikarya, which exhibit serotonin-like immunoreactivity, contact the tentacular neurite bundle, and are located near the youngest tentacles. Larvae have a minor nerve ring, which originates from the posterior marginal neurite bundle of the hood, passes above the tentacle base, and gives rise to the mediofrontal neurite bundle in each tentacle. Paired laterofrontal neurite bundles of tentacles form a continuous nerve tract that conducts to the postoral ciliated band. DISCUSSION The organization of the nervous system differs among the planktotrophic larvae of phoronid species. These differences may correlate with differences in phoronid biology. Data concerning the innervation of tentacles in different phoronid larvae are conflicting and require careful reinvestigation. The overall organization of the nervous system in phoronid larvae has more in common with the deuterostomian than with the protostomian nervous system. Phoronid larvae demonstrate some "deuterostome-like" features, which are, in fact, have to be ancestral bilaterian characters. Our new results and previous data indicate that phoronids have retained some plesiomorphic features, which were inherited from the last common ancestor of all Bilateria. It follows that phoronids should be extracted from the Trochozoan (=Spiralia) clade and placed at the base of the Lophotrochozoan stem.
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Affiliation(s)
- Elena N Temereva
- Department of Invertebrate Zoology, Biological faculty, Moscow State University, Moscow 119992, Russia.
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Sonnleitner B, Schwaha T, Wanninger A. Inter- and intraspecific plasticity in distribution patterns of immunoreactive compounds in actinotroch larvae of Phoronida (Lophotrochozoa). J ZOOL SYST EVOL RES 2013. [DOI: 10.1111/jzs.12043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Thomas Schwaha
- Department of Integrative Zoology; University of Vienna; Vienna Austria
| | - Andreas Wanninger
- Department of Integrative Zoology; University of Vienna; Vienna Austria
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HELM CONRAD, SCHEMEL SINA, BLEIDORN CHRISTOPH. Temporal Plasticity in Annelid Development-Ontogeny ofPhyllodoce groenlandica(Phyllodocidae, Annelida) Reveals Heterochronous Patterns. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 320:166-78. [DOI: 10.1002/jez.b.22492] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 01/18/2013] [Accepted: 01/22/2013] [Indexed: 11/09/2022]
Affiliation(s)
- CONRAD HELM
- Molecular Evolution & Systematics of Animals; Institute of Biology, University of Leipzig; Leipzig; Germany
| | - SINA SCHEMEL
- Molecular Evolution & Systematics of Animals; Institute of Biology, University of Leipzig; Leipzig; Germany
| | - CHRISTOPH BLEIDORN
- Molecular Evolution & Systematics of Animals; Institute of Biology, University of Leipzig; Leipzig; Germany
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Bright M, Eichinger I, von Salvini-Plawen L. The metatrochophore of a deep-sea hydrothermal vent vestimentiferan (Polychaeta: Siboglinidae). ORG DIVERS EVOL 2012; 13:163-188. [PMID: 26074729 PMCID: PMC4461187 DOI: 10.1007/s13127-012-0117-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 11/03/2012] [Indexed: 01/02/2023]
Abstract
Vestimentiferans (Siboglinidae, Polychaeta) live as juveniles and adults in an obligate mutualistic association with thiotrophic bacteria. Since their development is aposymbiotic, metatrochophores of vestimentiferans from the East Pacific Rise colonizing deep-sea hydrothermal vents are infected with the specific symbiont, develop the trophosome, and reduce their digestive system. To gain insight into the anatomy and ultrastructure and to compare this stage with metatrochophores from other siboglinids, we serial sectioned and reconstructed three specimens using light and transmission electron microscopy. The metatrochophore was composed of a prostomium, a small peristomium, two chaetigers (or two chaetigers and one additional segment without chaetae), and a minute pygidium. A digestive system and an intraepidermal nervous system were developed. Larval organs such as the prototroch, the neurotroch, and an apical organ were present, along with juvenile/adult organs such as tentacles, uncini, pyriform glands, and the anlage of the nephridial organ. We propose that in vestimentiferans, the vestimentum is the head arising from the prostomium, peristomium, and the anterior part of the first chaetiger. In frenulates, in contrast, the head is composed on the one hand of the cephalic lobe arising from the prostomium and on the other of the forepart developing from the peristomium and the anterior part of the first chaetiger. In frenulates the muscular septum between the forepart and trunk develops later than the first two chaetigers. Since this septum has no counterpart in vestimentiferans, the forepart-trunk border of frenulates is not considered homologous with the vestimentum-trunk border in vestimentiferans. The obturacular region in vestimentiferans does not appear to be a body region but rather the head appendages arising from the first chaetiger. In contrast, the tentacles in frenulates are prostomial head appendages. In both taxa, the trunk is the posterior part of the first chaetiger, and the opisthosoma is the following chaetigers and the pygidium. Comparisons with other polychaetes suggest that two larval segments are autapomorphic for the monophyletic Siboglinidae.
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Affiliation(s)
- Monika Bright
- Department of Marine Biology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
| | - Irmgard Eichinger
- Department of Marine Biology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
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Fofanova EG, Voronezhskaya EE. The structure of Archiannelid Dinophilus gyrociliatus ventral nerve cords. ACTA BIOLOGICA HUNGARICA 2012; 63 Suppl 2:88-90. [PMID: 22776479 DOI: 10.1556/abiol.63.2012.suppl.2.11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dinophilus gyrociliatus is a typical representative of the synthetic group Archiannelida. Here we describe the structure of Dinophilus young adults ventral nerve cords. Five nerve cords, irregular commissures and intersegmental nerves are revealed by tubulin and FMRFamide immunostaining. 5-HT-stainning marks the complex varicose nerve plexus with numerous irregularly distributed small perikarya. Four nerve cords and solitary cell bodies occur after clyoxylic-induced reaction for catecholamines visualization. Altogether, our results indicated that morphology of Dinophilus ventral nerve cords differs from the Polychaetes archetype in many respects.
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Affiliation(s)
- Elizaveta G Fofanova
- Department of Comparative Physiology, Institute of Developmental Biology RAS, Moscow, Russia
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Temereva E, Wanninger A. Development of the nervous system in Phoronopsis harmeri (Lophotrochozoa, Phoronida) reveals both deuterostome- and trochozoan-like features. BMC Evol Biol 2012; 12:121. [PMID: 22827441 PMCID: PMC3441923 DOI: 10.1186/1471-2148-12-121] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 06/06/2012] [Indexed: 11/10/2022] Open
Abstract
Background Inferences concerning the evolution of invertebrate nervous systems are often hampered by the lack of a solid data base for little known but phylogenetically crucial taxa. In order to contribute to the discussion concerning the ancestral neural pattern of the Lophotrochozoa (a major clade that includes a number of phyla that exhibit a ciliated larva in their life cycle), we investigated neurogenesis in Phoronopsis harmeri, a member of the poorly studied Phoronida, by using antibody staining against serotonin and FMRFamide in combination with confocal microscopy and 3D reconstruction software. Results The larva of Phoronopsis harmeri exhibits a highly complex nervous system, including an apical organ that consists of four different neural cell types, such as numerous serotonin-like immunoreactive flask-shaped cells. In addition, serotonin- and FMRFamide-like immunoreactive bi- or multipolar perikarya that give rise to a tentacular neurite bundle which innervates the postoral ciliated band are found. The preoral ciliated band is innervated by marginal serotonin-like as well as FMRFamide-like immunoreactive neurite bundles. The telotroch is innervated by two neurite bundles. The oral field is the most densely innervated area and contains ventral and ventro-lateral neurite bundles as well as several groups of perikarya. The digestive system is innervated by both serotonin- and FMRFamide-like immunoreactive neurites and perikarya. Importantly, older larvae of P. harmeri show a paired ventral neurite bundle with serial commissures and perikarya. Conclusions Serotonin-like flask-shaped cells such as the ones described herein for Phoronopsis harmeri are found in the majority of lophotrochozoan larvae and therefore most likely belong to the ground pattern of the last common lophotrochozoan ancestor. The finding of a transitory paired ventral neurite bundle with serially repeated commissures that disappears during metamorphosis suggests that such a structure was part of the “ur-phoronid” nervous system, but was lost in the adult stage, probably due to its acquired sessile benthic lifestyle.
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Affiliation(s)
- Elena Temereva
- Department of Invertebrate Zoology, Biological faculty, Moscow State University, Moscow 119991, Russia
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Santagata S, Resh C, Hejnol A, Martindale MQ, Passamaneck YJ. Development of the larval anterior neurogenic domains of Terebratalia transversa (Brachiopoda) provides insights into the diversification of larval apical organs and the spiralian nervous system. EvoDevo 2012; 3:3. [PMID: 22273002 PMCID: PMC3314550 DOI: 10.1186/2041-9139-3-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Accepted: 01/24/2012] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Larval features such as the apical organ, apical ciliary tuft, and ciliated bands often complicate the evaluation of hypotheses regarding the origin of the adult bilaterian nervous system. Understanding how neurogenic domains form within the bilaterian head and larval apical organ requires expression data from animals that exhibit aspects of both centralized and diffuse nervous systems at different life history stages. Here, we describe the expression of eight neural-related genes during the larval development of the brachiopod, Terebratalia transversa. RESULTS Radially symmetric gastrulae broadly express Tt-Six3/6 and Tt-hbn in the animal cap ectoderm. Tt-NK2.1 and Tt-otp are restricted to a central subset of these cells, and Tt-fez and Tt-FoxQ2 expression domains are already asymmetric at this stage. As gastrulation proceeds, the spatial expression of these genes is split between two anterior ectodermal domains, a more dorsal region comprised of Tt-Six3/6, Tt-fez, Tt-FoxQ2, and Tt-otp expression domains, and an anterior ventral domain demarcated by Tt-hbn and Tt-NK2.1 expression. More posteriorly, the latter domains are bordered by Tt-FoxG expression in the region of the transverse ciliated band. Tt-synaptotagmin 1 is expressed throughout the anterior neural ectoderm. All genes are expressed late into larval development. The basiepithelial larval nervous system includes three neurogenic domains comprised of the more dorsal apical organ and a ventral cell cluster in the apical lobe as well as a mid-ventral band of neurons in the mantle lobe. Tt-otp is the only gene expressed in numerous flask-shaped cells of the apical organ and in a subset of neurons in the mantle lobe. CONCLUSIONS Our expression data for Tt-Six3/6, Tt-FoxQ2, and Tt-otp confirm some aspects of bilaterian-wide conservation of spatial partitioning within anterior neurogenic domains and also suggest a common origin for central otp-positive cell types within the larval apical organs of spiralians. However, the field of sensory neurons within the larval apical organ of Terebratalia is broader and composed of more cells relative to those of other spiralian larvae. These cellular differences are mirrored in the broader spatial and temporal expression patterns of Tt-FoxQ2 and Tt-otp. Corresponding differences in the expression of Tt-hbn, Tt-NK2.1, and Tt-FoxG are also observed relative to their respective domains within the cerebral ganglia of spiralians. Based on these data we argue that the anterior region of the bilaterian stem species included Six3/6, NK2.1, otp, hbn, fez, and FoxQ2 expression domains that were subsequently modified within larval and adult neural tissues of protostome and deuterostome animals.
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Affiliation(s)
- Scott Santagata
- Long Island University-Post, 720 Northern Blvd., Brookville, NY 11709, USA
| | - Carlee Resh
- Long Island University-Post, 720 Northern Blvd., Brookville, NY 11709, USA
| | - Andreas Hejnol
- Sars International Center for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5008 Bergen, Norway
| | - Mark Q Martindale
- Kewalo Marine Laboratory, Pacific Biosciences Research Center, University of Hawaii, 41 Ahui Street, Honolulu, HI 96813, USA
| | - Yale J Passamaneck
- Kewalo Marine Laboratory, Pacific Biosciences Research Center, University of Hawaii, 41 Ahui Street, Honolulu, HI 96813, USA
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Abstract
Cilia-based locomotion is the major form of locomotion for microscopic planktonic organisms in the ocean. Given their negative buoyancy, these organisms must control ciliary activity to maintain an appropriate depth. The neuronal bases of depth regulation in ciliary swimmers are unknown. To gain insights into depth regulation we studied ciliary locomotor control in the planktonic larva of the marine annelid, Platynereis. We found several neuropeptides expressed in distinct sensory neurons that innervate locomotor cilia. Neuropeptides altered ciliary beat frequency and the rate of calcium-evoked ciliary arrests. These changes influenced larval orientation, vertical swimming, and sinking, resulting in upward or downward shifts in the steady-state vertical distribution of larvae. Our findings indicate that Platynereis larvae have depth-regulating peptidergic neurons that directly translate sensory inputs into locomotor output on effector cilia. We propose that the simple circuitry found in these ciliated larvae represents an ancestral state in nervous system evolution.
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Cummins SF, Tollenaere A, Degnan BM, Croll RP. Molecular analysis of two FMRFamide-encoding transcripts expressed during the development of the tropical abalone Haliotis asinina. J Comp Neurol 2011; 519:2043-59. [PMID: 21452226 DOI: 10.1002/cne.22621] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
FMRFamide-related peptides (FaRPs) are involved in numerous neural functions across the animal kingdom and serve as important models for understanding the evolution of neuropeptides. Gastropod molluscs have proved to be particularly useful foci for such studies, but the developmental expression of FaRPs and the evolution of specific transcripts for different peptides are unclear within the molluscs. Here we show that FaRPs are encoded by two transcripts that appear to be splice variants of a single gene in the abalone, Haliotis asinina, which represents the basal vetigastropods. Has-FMRF1 comprises 1,438 nucleotides and encodes a precursor protein of 329 amino acids that can potentially produce two copies of FLRFamide, one copy each of TLAGDSFLRFamide, QFYRIamide, SDPDLDDVIRASLLAYSLDDSPNN, and SVATAPVEAKAVEAGNKDIE, and 13 copies of FMRFamide. The second 1,241-nucleotide transcript, Has-FMRF2, encodes a 206-amino acid precursor protein with single copies of FLRFamide and FMRFamide along with such extended forms as NFGEPFLRFamide, FDSYEDKALRFamide, and NGWLHFamide, in addition to SDPGEDMLKSILLRGAPSNNGLQY and DTUDETTUNDNAHSRQ. Both transcripts are present early in life and are expressed in different but overlapping patterns within the developing larval nervous system. Mass spectrometry and immunocytochemistry demonstrate that FaRPs are cleaved from larger precursors and localize to the developing nervous system. Our results confirm previous evidence that FaRPs are expressed early and potentially play many roles during molluscan development and suggest that the last common ancestor to living gastropods used alternative splicing of an FMRFamide gene to generate a diversity of FaRPs in spatially restricted patterns in the nervous system.
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Affiliation(s)
- Scott F Cummins
- School of Biological Sciences, The University of Queensland, Brisbane, 4072, Australia
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Temereva EN. Ventral nerve cord in Phoronopsis harmeri larvae. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2011; 318:26-34. [DOI: 10.1002/jez.b.21437] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 07/15/2011] [Accepted: 07/20/2011] [Indexed: 01/19/2023]
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Voronezhskaya EE, Ivashkin EG. Pioneer neurons: A basis or limiting factor of lophotrochozoa nervous system diversity? Russ J Dev Biol 2010. [DOI: 10.1134/s1062360410060019] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Nezlin LP. The golden age of comparative morphology: Laser scanning microscopy and neurogenesis in trochophore animals. Russ J Dev Biol 2010. [DOI: 10.1134/s1062360410060056] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Brinkmann N, Wanninger A. Capitellid connections: contributions from neuromuscular development of the maldanid polychaete Axiothella rubrocincta (Annelida). BMC Evol Biol 2010; 10:168. [PMID: 20529306 PMCID: PMC2897808 DOI: 10.1186/1471-2148-10-168] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2009] [Accepted: 06/08/2010] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Numerous phylogenetic analyses on polychaete annelids suggest a taxon Capitellida that comprises the three families Maldanidae, Arenicolidae and Capitellidae. Recent molecular studies support the position of the Echiura, traditionally ranked as a separate phylum, within the capitellids. In order to test the robustness of this molecular-based hypothesis we take a different approach using comparative analyses of nervous and muscle system development in the maldanid Axiothella rubrocincta. Employing immunocytochemistry in combination with confocal laserscanning microscopy, we broaden the database on capitellid organogenesis, thereby incorporating classical histological data in our analysis. Besides assessing possible shared features with the echiurans, we also discuss the variability of neural and muscular characters within the Capitellida. RESULTS The scaffold of the adult central nervous system, which is already established in early developmental stages of Axiothella, consists of cerebral commissures that give rise to simple circumesophageal connectives with fused ventral and dorsal roots and a single ventral neurite bundle. From the latter arise segmental neurites that innervate the peripheral bodywall. Since there is no observable regular pattern, and individual neurites are lost during ontogeny, their exact arrangement remains elusive. The pharynx is encircled by a prominent stomatogastric nerve ring, with a pair of anterior and lateral proboscis neurites directly connecting it to the central nervous system. One pair of ventral and one pair of dorsal longitudinal muscles form the earliest rudiments of the bodywall musculature in late larval stages, while a continuous layer of circular muscles is lacking throughout ontogeny. CONCLUSIONS Comparative neurodevelopmental analysis of capitellid and echiuran species reveals several common characters, including simple circumesophageal connectives, a single fused ventral nerve strand, and a stomatogastric ring nerve, that support a close relationship of both taxa, thus corroborating recent molecular phylogenetic analyses. The data on myogenesis show that four longitudinal muscle bands most likely represent an ancestral character not only for the Capitellida, but for the Annelida in general. Whether or not circular muscles are part of the annelid groundpattern remains uncertain.
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Affiliation(s)
- Nora Brinkmann
- Department of Biology, Research Group for Comparative Zoology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
| | - Andreas Wanninger
- Department of Biology, Research Group for Comparative Zoology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
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Altenburger A, Wanninger A. Neuromuscular development in Novocrania anomala: evidence for the presence of serotonin and a spiralian-like apical organ in lecithotrophic brachiopod larvae. Evol Dev 2010; 12:16-24. [PMID: 20156279 DOI: 10.1111/j.1525-142x.2009.00387.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The phylogenetic position of Brachiopoda remains unsettled, and only few recent data on brachiopod organogenesis are currently available. In order to contribute data to questions concerning brachiopod ontogeny and evolution we investigated nervous and muscle system development in the craniiform (inarticulate) brachiopod Novocrania anomala. Larvae of this species are lecithotrophic and have a bilobed body with three pairs of dorsal setal bundles that emerge from the posterior lobe. Fully developed larvae exhibit a network of setae pouch muscles as well as medioventral longitudinal and transversal muscles. After settlement, the anterior and posterior adductor muscles and delicate mantle retractor muscles begin to form. Comparison of the larval muscular system of Novocrania anomala with that of rhynchonelliform (articulate) brachiopod larvae shows that the former has a much simpler muscular organization. The first signal of serotonin-like immunoreactivity appears in fully developed Novocrania anomala larvae, which have an apical organ that consists of four flask-shaped cells and two ventral neurites. These ventral neurites do not stain positively for the axonal marker alpha-tubulin in the larval stages. In the juveniles, the nervous system stained by alpha-tubulin is characterized by two ventral neurite bundles with three commissures. Our data are the first direct proof for the presence of an immunoreactive neurotransmitter in lecithotrophic brachiopod larvae and demonstrate the existence of flask-shaped serotonergic cells in the brachiopod larval apical organ, thus significantly increasing the probability that this cell type was part of the bauplan of the larvae of the last common lophotrochozoan ancestor.
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Affiliation(s)
- Andreas Altenburger
- Department of Biology, Research Group for Comparative Zoology, University of Copenhagen, Universitetsparken 15, Copenhagen Ø, Denmark
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Rawlinson KA. Embryonic and post-embryonic development of the polyclad flatworm Maritigrella crozieri; implications for the evolution of spiralian life history traits. Front Zool 2010; 7:12. [PMID: 20426837 PMCID: PMC2876153 DOI: 10.1186/1742-9994-7-12] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 04/28/2010] [Indexed: 11/28/2022] Open
Abstract
Background Planktonic life history stages of spiralians share some muscular, nervous and ciliary system characters in common. The distribution of these characters is patchy and can be interpreted either as the result of convergent evolution, or as the retention of primitive spiralian larval features. To understand the evolution of these characters adequate taxon sampling across the Spiralia is necessary. Polyclad flatworms are the only free-living Platyhelminthes that exhibit a continuum of developmental modes, with direct development at one extreme, and indirect development via a trochophore-like larval stage at the other. Here I present embryological and larval anatomical data from the indirect developing polyclad Maritrigrella crozieri, and consider these data within a comparative spiralian context. Results After 196 h hours of embryonic development, M. crozieri hatches as a swimming, planktotrophic larva. Larval myoanatomy consists of an orthogonal grid of circular and longitudinal body wall muscles plus parenchymal muscles. Diagonal body wall muscles develop over the planktonic period. Larval neuroanatomy consists of an apical plate, neuropile, paired nerve cords, a peri-oral nerve ring, a medial nerve, a ciliary band nerve net and putative ciliary photoreceptors. Apical neural elements develop first followed by posterior perikarya and later pharyngeal neural elements. The ciliated larva is encircled by a continuous, pre-oral band of longer cilia, which follows the distal margins of the lobes; it also possesses distinct apical and caudal cilia. Conclusions Within polyclads heterochronic shifts in the development of diagonal bodywall and pharyngeal muscles are correlated with life history strategies and feeding requirements. In contrast to many spiralians, M. crozieri hatch with well developed nervous and muscular systems. Comparisons of the ciliary bands and apical organs amongst spiralian planktonic life-stages reveal differences; M. crozieri lack a distinct ciliary band muscle and flask-shaped epidermal serotonergic cells of the apical organ. Based on current phylogenies, the distribution of ciliary bands and apical organs between polyclads and other spiralians is not congruent with a hypothesis of homology. However, some similarities exist, and this study sets an anatomical framework from which to investigate cellular and molecular mechanisms that will help to distinguish between parallelism, convergence and homology of these features.
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Affiliation(s)
- Kate A Rawlinson
- Smithsonian Marine Station, 701 Seaway Drive, Fort Pierce, Florida, 34949 USA.
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Worsaae K, Rouse GW. The simplicity of males: dwarf males of four species of Osedax (Siboglinidae; Annelida) investigated by confocal laser scanning microscopy. J Morphol 2010; 271:127-42. [PMID: 19658166 DOI: 10.1002/jmor.10786] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dwarf males of the bone-eating worms Osedax (Siboglinidae, Annelida) have been proposed to develop from larvae that settle on females rather than on bone. The apparent arrest in somatic development and resemblance of the males to trochophore larvae has been posited as an example of paedomorphosis. Here, we present the first investigation of the entire muscle and nervous system in dwarf males of Osedax frankpressi, O. roseus, O. rubiplumus, and O. "spiral" analyzed by multistaining and confocal laser scanning microscopy. Sperm shape and spermiogenesis, the sperm duct and internal and external ciliary patterns were likewise visualized. The males of all four species possess morphological traits typical of newly settled siboglinid larvae: a prostomium, a peristomium with a prototroch, one elongate segment and a second shorter segment. Each segment has a ring of eight long-handled hooked chaetae. The longitudinal muscles are distributed as evenly spaced strands forming a grid with the thin outer circular muscles. Oblique protractor and retractor muscles are associated with each of the chaetal sacs. The nervous system comprises a cerebral ganglion, a prototroch nerve ring, paired dorsolateral longitudinal nerves, five ventral longitudinal nerves with paired, posterior ganglia and a terminal commissure, as well as a net of fine peripheral transverse plexuses surrounding the first segment. Internal ciliation occurs as paired ventrolateral bands along the first segment. The bands appear to lead the free mature sperm to a ciliated duct and seminal vesicle lying just behind the prototroch region. A duct then runs from the seminal vesicle into the dorsal part of the prostomium. The similarity of Osedax males to the larvae of Osedax and other siboglinid annelids as well as similarities shown here to the neuromuscular organization seen in other annelid larvae supports the hypothesis of paedomorphosis in males of Osedax.
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Affiliation(s)
- Katrine Worsaae
- Marine Biological Laboratory, Department of Biology, University of Copenhagen, 3000 Helsingør, Denmark
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Brinkmann N, Wanninger A. Neurogenesis suggests independent evolution of opercula in serpulid polychaetes. BMC Evol Biol 2009; 9:270. [PMID: 19930667 PMCID: PMC2785788 DOI: 10.1186/1471-2148-9-270] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 11/23/2009] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND The internal phylogenetic relationships of Annelida, one of the key lophotrochozoan lineages, are still heavily debated. Recent molecular analyses suggest that morphologically distinct groups, such as the polychaetes, are paraphyletic assemblages, thus questioning the homology of a number of polychaete morphological characters. Serpulid polychaetes are typically recognized by having fused anterior ends bearing a tentacular crown and an operculum. The latter is commonly viewed as a modified tentacle (= radiole) and is often used as an important diagnostic character in serpulid systematics. RESULTS By reconstructing the developmental neuroanatomy of the serpulid polychaete Spirorbis cf. spirorbis (Spirorbinae), we found striking differences in the overall neural architecture, the innervation pattern, and the ontogenetic establishment of the nervous supply of the operculum and the radioles in this species. Accordingly, the spirorbin operculum might not be homologous to the radioles or to the opercula of other serpulid taxa such as Serpula and Pomatoceros and is thus probably not a part of the tentacular crown. CONCLUSION We demonstrate that common morphological traits such as the prostomial appendages may have evolved independently in respective serpulid sublineages and therefore require reassessment before being used in phylogenetic analyses. Our findings corroborate recent molecular studies that argue for a revision of serpulid systematics. In addition, our data on Spirorbis neurogenesis provide a novel set of characters that highlight the developmental plasticity of the segmented annelid nervous system.
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Affiliation(s)
- Nora Brinkmann
- Department of Biology, Research Group for Comparative Zoology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
| | - Andreas Wanninger
- Department of Biology, Research Group for Comparative Zoology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
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Wanninger A. Shaping the things to come: ontogeny of lophotrochozoan neuromuscular systems and the tetraneuralia concept. THE BIOLOGICAL BULLETIN 2009; 216:293-306. [PMID: 19556595 DOI: 10.1086/bblv216n3p293] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Despite the large variation in adult bodyplan phenotypes, a worm-shaped morphology is considered plesiomorphic for both Lophotrochozoa and Bilateria. Although almost all larval and adult lophotrochozoan worms have serially arranged ring muscles in their body wall, a comparison of their ontogeny reveals no less than six different developmental pathways that lead to this homogenous arrangement of ring muscles. However, in all taxa, with the exception of chaetodermomorph molluscs and the segmented annelids, ring muscle development starts with synchronous formation of certain pioneer myocytes, which is thus considered basal for Lophotrochozoa. Recent studies on spiralian neurogenesis revealed remnants of ancestral segmentation in echiurans and sipunculans, thus confirming molecular phylogenetic studies that propose a close relationship of these three taxa. Larval entoprocts exhibit a mosaic of larval and adult molluscan characters and, among other apomorphies, share with polyplacophoran Mollusca a complex larval apical organ and a tetraneurous nervous system, strongly suggesting a monophyletic assemblage of Entoprocta and Mollusca. The term Tetraneuralia is proposed herein for this lophotrochozoan clade. Overall, formation of the lophotrochozoan neuromuscular bodyplan appears as a highly dynamic process on both the ontogenetic and the evolutionary timescales, highlighting the importance of insights into these processes for reconstructing ancestral bodyplan features and phylogenetic relationships.
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Affiliation(s)
- Andreas Wanninger
- University of Copenhagen, Department of Biology, Research Group for Comparative Zoology, Universitetsparken 15, DK-2100 Copenhagen, Denmark.
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Arenas-Mena C. The transcription factorsHeBlimpandHeT-brainof an indirectly developing polychaete suggest ancestral endodermal, gastrulation, and sensory cell-type specification roles. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2008; 310:567-76. [DOI: 10.1002/jez.b.21225] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Kristof A, Wollesen T, Wanninger A. Segmental mode of neural patterning in sipuncula. Curr Biol 2008; 18:1129-32. [PMID: 18656359 DOI: 10.1016/j.cub.2008.06.066] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 05/29/2008] [Accepted: 06/18/2008] [Indexed: 10/21/2022]
Abstract
Recent molecular phylogenetic analyses suggest a close relationship between two worm-shaped phyla, the nonsegmented Sipuncula (peanut worms) and the segmented Annelida (e.g., earthworms and polychaetes) [1-5]. The striking differences in their bodyplans are exemplified by the annelids' paired, ladder-like ventral nervous system, which contains segmentally arranged ganglia, and the sipunculans' single ventral nerve cord (VNC), which is devoid of any segmental structures [6, 7]. Investigating central nervous system (CNS) formation with serotonin and FMRFamide labeling in a representative sipunculan, Phascolosoma agassizii, we found that neurogenesis initially follows a segmental pattern similar to that of annelids. Starting out with paired FMRFamidergic and serotonergic axons, four pairs of associated serotonergic perikarya and interconnecting commissures form one after another in an anterior-posterior progression. In late-stage larvae, the two serotonergic axons of the VNCs fuse, the commissures disappear, and one additional pair of perikarya is formed. These cells (ten in total) migrate toward one another, eventually forming two clusters of five cells each. These neural-remodeling processes result in the single nonmetameric CNS of the adult sipunculan. Our data confirm the segmental ancestry of Sipuncula and render Phascolosoma a textbook example for the Haeckelian hypothesis of ontogenetic recapitulation of the evolutionary history of a species [8].
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Affiliation(s)
- Alen Kristof
- Department of Biology, Research Group for Comparative Zoology, University of Copenhagen, Copenhagen DK-2100, Denmark
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Voronezhskaya EE, Nezlin LP, Odintsova NA, Plummer JT, Croll RP. Neuronal development in larval mussel Mytilus trossulus (Mollusca: Bivalvia). ZOOMORPHOLOGY 2008. [DOI: 10.1007/s00435-007-0055-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Mashaly A, Winkler M, Frambach I, Gras H, Schürmann FW. Sprouting interneurons in mushroom bodies of adult cricket brains. J Comp Neurol 2008; 508:153-74. [DOI: 10.1002/cne.21660] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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