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Arango CP, Brenneis G. Epimorphic development in tropical shallow-water Nymphonidae (Arthropoda: Pycnogonida) revealed by fluorescence imaging. ZOOLOGICAL LETTERS 2024; 10:1. [PMID: 38167377 PMCID: PMC10759633 DOI: 10.1186/s40851-023-00223-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 11/11/2023] [Indexed: 01/05/2024]
Abstract
BACKGROUND Extant lineages of sea spiders (Pycnogonida) exhibit different types of development. Most commonly, pycnogonids hatch as a minute, feeding protonymphon larva with subsequent anamorphic development. However, especially in cold water habitats at higher latitudes and in the deep sea, some taxa have large, lecithotrophic larvae, or even undergo extended embryonic development with significantly advanced postlarval hatching stages. Similar biogeographic trends are observed in other marine invertebrates, often referred to as "Thorson's rule". RESULTS To expand our knowledge on the developmental diversity in the most speciose pycnogonid genus Nymphon, we studied the developmental stages of the two tropical representatives N. floridanum and N. micronesicum., We compared classical scanning electron microscopy with fluorescence-based approaches to determine which imaging strategy is better suited for the ethanol-fixed material available. Both species show epimorphic development and hatch as an advanced, lecithotrophic postlarval instar possessing the anlagen of all body segments. Leg pairs 1-3 show a considerable degree of differentiation at hatching, but their proximal regions remain coiled and hidden under the cuticle of the hatching instar. The adult palp and oviger are not anteceded by three-articled larval limbs, but differentiate directly from non-articulated limb buds during postembryonic development. CONCLUSIONS Fluorescence imaging yielded more reliable morphological data than classical scanning electron microscopy, being the method of choice for maximal information gain from rare and fragile sea spider samples fixed in high-percentage ethanol. The discovery of epimorphic development with lecithotrophic postlarval instars in two small Nymphon species from tropical shallow-water habitats challenges the notion that this developmental pathway represents an exclusive cold-water adaptation in Nymphonidae. Instead, close phylogenetic affinities to the likewise more direct-developing Callipallenidae hint at a common evolutionary origin of this trait in the clade Nymphonoidea (Callipallenidae + Nymphonidae). The lack of functional palpal and ovigeral larval limbs in callipallenids and postlarval hatchers among nymphonids may be a derived character of Nymphonoidea. To further test this hypothesis, a stable and well-resolved phylogenetic backbone for Nymphonoidea is key.
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Affiliation(s)
- Claudia P Arango
- Queensland Museum, Biodiversity Program, PO Box 3300, South Brisbane, QLD, 4101, Australia
| | - Georg Brenneis
- Department Evolutionary Biology, Unit Integrative Zoology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria.
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Prpic NM, Pechmann M. Extraembryonic tissue in chelicerates: a review and outlook. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210269. [PMID: 36252223 PMCID: PMC9574639 DOI: 10.1098/rstb.2021.0269] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 04/16/2022] [Indexed: 01/03/2023] Open
Abstract
The formation of extraembryonic membranes (EEMs) contributes to the proper development of many animals. In arthropods, the formation and function of EEMs have been studied best in insects. Regarding the development of extraembryonic tissue in chelicerates (spiders and relatives), most information is available for spiders (Araneae). Especially two populations of cells have been considered to represent EEMs in spiders. The first of these potential EEMs develops shortly after egg deposition, opposite to a radially symmetrical germ disc that forms in one hemisphere of the egg and encloses the yolk. The second tissue, which has been described as being extraembryonic is the so-called dorsal field, which is required to cover the dorsal part of the developing spider germ rudiment before proper dorsal closure. In this review, we summarize the current knowledge regarding the formation of potential extraembryonic structures in the Chelicerata. We describe the early embryogenesis of spiders and other chelicerates, with a special focus on the formation of the potential extraembryonic tissues. This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'.
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Affiliation(s)
- Nikola-Michael Prpic
- Justus-Liebig-Universitaet Giessen, Institut für Allgemeine Zoologie und Entwicklungsbiologie, AG Zoologie mit dem Schwerpunkt Molekulare Entwicklungsbiologie, Heinrich-Buff-Ring 38, 35392 Giessen, Germany
| | - Matthias Pechmann
- Institute for Zoology, University of Cologne, Biocenter, Zuelpicher Strasse 47b, 50674 Cologne, Germany
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Alexeeva N, Tamberg Y, Shunatova N. The (not very) typical protonymphons of
Pycnogonum litorale. J Morphol 2019; 280:1370-1392. [DOI: 10.1002/jmor.21038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 06/12/2019] [Accepted: 06/16/2019] [Indexed: 01/09/2023]
Affiliation(s)
- Nina Alexeeva
- Department of Invertebrate ZoologySt. Petersburg State University St. Petersburg Russian Federation
| | - Yuta Tamberg
- Department of Marine ScienceUniversity of Otago Dunedin New Zealand
| | - Natalia Shunatova
- Department of Invertebrate ZoologySt. Petersburg State University St. Petersburg Russian Federation
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Brenneis G, Scholtz G, Beltz BS. Comparison of ventral organ development across Pycnogonida (Arthropoda, Chelicerata) provides evidence for a plesiomorphic mode of late neurogenesis in sea spiders and myriapods. BMC Evol Biol 2018; 18:47. [PMID: 29621973 PMCID: PMC5887176 DOI: 10.1186/s12862-018-1150-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 03/06/2018] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Comparative studies of neuroanatomy and neurodevelopment provide valuable information for phylogenetic inference. Beyond that, they reveal transformations of neuroanatomical structures during animal evolution and modifications in the developmental processes that have shaped these structures. In the extremely diverse Arthropoda, such comparative studies contribute with ever-increasing structural resolution and taxon coverage to our understanding of nervous system evolution. However, at the neurodevelopmental level, in-depth data remain still largely confined to comparably few laboratory model organisms. Therefore, we studied postembryonic neurogenesis in six species of the bizarre Pycnogonida (sea spiders), which - as the likely sister group of all remaining chelicerates - promise to illuminate neurodevelopmental changes in the chelicerate lineage. RESULTS We performed in vivo cell proliferation experiments with the thymidine analogs 5-bromo-2'-deoxyuridine and 5-ethynl-2'-deoxyuridine coupled to fluorescent histochemical staining and immunolabeling, in order to compare ventral nerve cord anatomy and to localize and characterize centers of postembryonic neurogenesis. We report interspecific differences in the architecture of the subesophageal ganglion (SEG) and show the presence of segmental "ventral organs" (VOs) that act as centers of neural cell production during gangliogenesis. These VOs are either incorporated into the ganglionic soma cortex or found on the external ganglion surface. Despite this difference, several shared features support homology of the two VO types, including (1) a specific arrangement of the cells around a small central cavity, (2) the presence of asymmetrically dividing neural stem cell-like precursors, (3) the migration of newborn cells along corresponding pathways into the cortex, and (4) the same VO origin and formation earlier in development. CONCLUSIONS Evaluation of our findings relative to current hypotheses on pycnogonid phylogeny resolves a bipartite SEG and internal VOs as plesiomorphic conditions in pycnogonids. Although chelicerate taxa other than Pycnogonida lack comparable VOs, they are a characteristic feature of myriapod gangliogenesis. Accordingly, we propose internal VOs with neurogenic function to be part of the ground pattern of Arthropoda. Further, our findings illustrate the importance of dense sampling in old arthropod lineages - even if as gross-anatomically uniform as Pycnogonida - in order to reliably differentiate plesiomorphic from apomorphic neurodevelopmental characteristics prior to outgroup comparison.
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Affiliation(s)
- Georg Brenneis
- Wellesley College, Neuroscience Program, 106 Central Street, Wellesley, MA, 02481, USA. .,Humboldt-Universität zu Berlin, Institut für Biologie, Vergleichende Zoologie, Philippstraße 13, Haus 2, 10115, Berlin, Germany.
| | - Gerhard Scholtz
- Humboldt-Universität zu Berlin, Institut für Biologie, Vergleichende Zoologie, Philippstraße 13, Haus 2, 10115, Berlin, Germany
| | - Barbara S Beltz
- Wellesley College, Neuroscience Program, 106 Central Street, Wellesley, MA, 02481, USA
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Feitosa NM, Pechmann M, Schwager EE, Tobias-Santos V, McGregor AP, Damen WGM, Nunes da Fonseca R. Molecular control of gut formation in the spider Parasteatoda tepidariorum. Genesis 2017; 55. [PMID: 28432834 DOI: 10.1002/dvg.23033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 02/23/2017] [Accepted: 03/16/2017] [Indexed: 12/16/2022]
Abstract
The development of a digestive system is an essential feature of bilaterians. Studies of the molecular control of gut formation in arthropods have been studied in detail in the fruit fly Drosophila melanogaster. However, little is known in other arthropods, especially in noninsect arthropods. To better understand the evolution of arthropod alimentary system, we investigate the molecular control of gut development in the spider Parasteatoda tepidariorum (Pt), the primary chelicerate model species for developmental studies. Orthologs of the ectodermal genes Pt-wingless (Pt-wg) and Pt-hedgehog (Pt-hh), of the endodermal genes, Pt-serpent (Pt-srp) and Pt-hepatocyte-nuclear factor-4 (Pt-hnf4) and of the mesodermal gene Pt-twist (Pt-twi) are expressed in the same germ layers during spider gut development as in D. melanogaster. Thus, our expression data suggest that the downstream molecular components involved in gut development in arthropods are conserved. However, Pt-forkhead (Pt-fkh) expression and function in spiders is considerably different from its D. melanogaster ortholog. Pt-fkh is expressed before gastrulation in a cell population that gives rise to endodermal and mesodermal precursors, suggesting a possible role for this factor in specification of both germ layers. To test this hypothesis, we knocked down Pt-fkh via RNA interference. Pt-fkh RNAi embryos not only fail to develop a proper gut, but also lack the mesodermal Pt-twi expressing cells. Thus, in spiders Pt-fkh specifies endodermal and mesodermal germ layers. We discuss the implications of these findings for the evolution and development of gut formation in Ecdysozoans.
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Affiliation(s)
- Natália Martins Feitosa
- Laboratório Integrado de Ciências Morfofuncionais, Núcleo em Ecologia e Desenvolvimento Socio-Ambiental de Macaé (NUPEM), Campus Macaé, Universidade Federal do Rio de Janeiro (UFRJ), Macaé, Rio de Janeiro, 27920-560, Brazil
| | - Matthias Pechmann
- Institute for Developmental Biology, University of Cologne, Cologne, North-Rhine Westphalia, 50674, Germany
| | - Evelyn E Schwager
- Department of Biological Sciences, University of Massachusetts Lowell, 198 Riverside Street, Lowell, Massachusetts, 01854
| | - Vitória Tobias-Santos
- Laboratório Integrado de Ciências Morfofuncionais, Núcleo em Ecologia e Desenvolvimento Socio-Ambiental de Macaé (NUPEM), Campus Macaé, Universidade Federal do Rio de Janeiro (UFRJ), Macaé, Rio de Janeiro, 27920-560, Brazil
| | - Alistair P McGregor
- Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, United Kingdom
| | - Wim G M Damen
- Department of Genetics, Friedrich-Schiller-Universität Jena, Philosophenweg 12, Jena, 07743, Germany
| | - Rodrigo Nunes da Fonseca
- Laboratório Integrado de Ciências Morfofuncionais, Núcleo em Ecologia e Desenvolvimento Socio-Ambiental de Macaé (NUPEM), Campus Macaé, Universidade Federal do Rio de Janeiro (UFRJ), Macaé, Rio de Janeiro, 27920-560, Brazil.,Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular (INCT-EM), Universidade Federal do Rio de Janeiro (UFRJ), 21941-599 Rio de Janeiro, Rio de Janeiro, Brazil
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Brenneis G, Bogomolova EV, Arango CP, Krapp F. From egg to "no-body": an overview and revision of developmental pathways in the ancient arthropod lineage Pycnogonida. Front Zool 2017; 14:6. [PMID: 28191025 PMCID: PMC5297176 DOI: 10.1186/s12983-017-0192-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 01/23/2017] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Arthropod diversity is unparalleled in the animal kingdom. The study of ontogeny is pivotal to understand which developmental processes underlie the incredible morphological disparity of arthropods and thus to eventually unravel evolutionary transformations leading to their success. Work on laboratory model organisms has yielded in-depth data on numerous developmental mechanisms in arthropods. Yet, although the range of studied taxa has increased noticeably since the advent of comparative evolutionary developmental biology (evo-devo), several smaller groups remain understudied. This includes the bizarre Pycnogonida (sea spiders) or "no-bodies", a taxon occupying a crucial phylogenetic position for the interpretation of arthropod development and evolution. RESULTS Pycnogonid development is variable at familial and generic levels and sometimes even congeneric species exhibit different developmental modes. Here, we summarize the available data since the late 19th century. We clarify and resolve terminological issues persisting in the pycnogonid literature and distinguish five developmental pathways, based on (1) type of the hatching stage, (2) developmental-morphological features during postembryonic development and (3) selected life history characteristics. Based on phylogenetic analyses and the fossil record, we discuss plausible plesiomorphic features of pycnogonid development that allow comparison to other arthropods. These features include (1) a holoblastic, irregular cleavage with equal-sized blastomeres, (2) initiation of gastrulation by a single bottle-shaped cell, (3) the lack of a morphologically distinct germ band during embryogenesis, (4) a parasitic free-living protonymphon larva as hatching stage and (5) a hemianamorphic development during the postlarval and juvenile phases. Further, we propose evolutionary developmental trajectories within crown-group Pycnogonida. CONCLUSIONS A resurgence of studies on pycnogonid postembryonic development has provided various new insights in the last decades. However, the scarcity of modern-day embryonic data - including the virtual lack of gene expression and functional studies - needs to be addressed in future investigations to strengthen comparisons to other arthropods and arthropod outgroups in the framework of evo-devo. Our review may serve as a basis for an informed choice of target species for such studies, which will not only shed light on chelicerate development and evolution but furthermore hold the potential to contribute important insights into the anamorphic development of the arthropod ancestor.
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Affiliation(s)
- Georg Brenneis
- Wellesley College, Neuroscience Program, 106 Central Street, Wellesley, MA 02481 USA
| | | | - Claudia P. Arango
- Queensland Museum, Biodiversity Program, PO Box 3300, South Brisbane, QLD 4101 Australia
| | - Franz Krapp
- Zoologisches Forschungsmuseum A. Koenig, Adenauerallee 160, D-53113 Bonn, Germany
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7
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Scholtz G, Brenneis G. The pattern of a specimen of Pycnogonum litorale (Arthropoda, Pycnogonida) with a supernumerary leg can be explained with the "boundary model" of appendage formation. Naturwissenschaften 2016; 103:13. [PMID: 26830781 PMCID: PMC4735254 DOI: 10.1007/s00114-016-1333-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 01/07/2016] [Accepted: 01/11/2016] [Indexed: 11/28/2022]
Abstract
A malformed adult female specimen of Pycnogonum litorale (Pycnogonida) with a supernumerary leg in the right body half is described concerning external and internal structures. The specimen was maintained in our laboratory culture after an injury in the right trunk region during a late postembryonic stage. The supernumerary leg is located between the second and third walking legs. The lateral processes connecting to these walking legs are fused to one large structure. Likewise, the coxae 1 of the second and third walking legs and of the supernumerary leg are fused to different degrees. The supernumerary leg is a complete walking leg with mirror image symmetry as evidenced by the position of joints and muscles. It is slightly smaller than the normal legs, but internally, it contains a branch of the ovary and a gut diverticulum as the other legs. The causes for this malformation pattern found in the Pycnogonum individual are reconstructed in the light of extirpation experiments in insects, which led to supernumerary mirror image legs, and the “boundary model” for appendage differentiation.
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Affiliation(s)
- Gerhard Scholtz
- Humboldt-Universität zu Berlin, Institut für Biologie, Vergleichende Zoologie, Philippstr. 13, 10115, Berlin, Germany.
| | - Georg Brenneis
- Humboldt-Universität zu Berlin, Institut für Biologie, Vergleichende Zoologie, Philippstr. 13, 10115, Berlin, Germany.,Neuroscience Program, Wellesley College, 106 Central Street, Wellesley, MA, 02481, USA
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Martín-Durán JM, Hejnol A. The study of Priapulus caudatus reveals conserved molecular patterning underlying different gut morphogenesis in the Ecdysozoa. BMC Biol 2015; 13:29. [PMID: 25895830 PMCID: PMC4434581 DOI: 10.1186/s12915-015-0139-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 04/13/2015] [Indexed: 12/14/2022] Open
Abstract
Background The digestive systems of animals can become highly specialized in response to their exploration and occupation of new ecological niches. Although studies on different animals have revealed commonalities in gut formation, the model systems Caenorhabditis elegans and Drosophila melanogaster, which belong to the invertebrate group Ecdysozoa, exhibit remarkable deviations in how their intestines develop. Their morphological and developmental idiosyncrasies have hindered reconstructions of ancestral gut characters for the Ecdysozoa, and limit comparisons with vertebrate models. In this respect, the phylogenetic position, and slow evolving morphological and molecular characters of marine priapulid worms advance them as a key group to decipher evolutionary events that occurred in the lineages leading to C. elegans and D. melanogaster. Results In the priapulid Priapulus caudatus, the gut consists of an ectodermal foregut and anus, and a mid region of at least partial endodermal origin. The inner gut develops into a 16-cell primordium devoid of visceral musculature, arranged in three mid tetrads and two posterior duplets. The mouth invaginates ventrally and shifts to a terminal anterior position as the ventral anterior ectoderm differentially proliferates. Contraction of the musculature occurs as the head region retracts into the trunk and resolves the definitive larval body plan. Despite obvious developmental differences with C. elegans and D. melanogaster, the expression in P. caudatus of the gut-related candidate genes NK2.1, foxQ2, FGF8/17/18, GATA456, HNF4, wnt1, and evx demonstrate three distinct evolutionarily conserved molecular profiles that correlate with morphologically identified sub-regions of the gut. Conclusions The comparative analysis of priapulid development suggests that a midgut formed by a single endodermal population of vegetal cells, a ventral mouth, and the blastoporal origin of the anus are ancestral features in the Ecdysozoa. Our molecular data on P. caudatus reveal a conserved ecdysozoan gut-patterning program and demonstrates that extreme morphological divergence has not been accompanied by major molecular innovations in transcriptional regulators during digestive system evolution in the Ecdysozoa. Our data help us understand the origins of the ecdysozoan body plan, including those of C. elegans and D. melanogaster, and this is critical for comparisons between these two prominent model systems and their vertebrate counterparts. Electronic supplementary material The online version of this article (doi:10.1186/s12915-015-0139-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- José M Martín-Durán
- Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5008, Bergen, Norway.
| | - Andreas Hejnol
- Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5008, Bergen, Norway.
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Alwes F, Scholtz G. The early development of the onychopod cladoceran Bythotrephes longimanus (Crustacea, Branchiopoda). Front Zool 2014; 11:10. [PMID: 24507018 PMCID: PMC3930293 DOI: 10.1186/1742-9994-11-10] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 01/30/2014] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION Within arthropods, several crustacean groups are unique in their early development due to their stereotyped cell division patterns and cell lineages. However, it is still unclear whether these cell division patterns are homologous between the various crustacean groups and whether they could indicate the ground pattern of Tetraconata (Crustacea and Hexapoda). In this study we describe the early development of the raptorial water flea Bythotrephes longimanus as a representative of the Cladocera within branchiopods. RESULTS In B. longimanus the early cell lineage and the cell division pattern are stereotyped up to the fifth cell division cycle. As a morphological marker a nurse cell remnant (ncr) identifies the cell lineage of the smallest and division delayed blastomere up to the 16-cell stage. This marker might be indicative of the germ line. By combining histology, confocal laser scanning microscopy, and 4D microscopy, we reconstruct the early cell lineage and cell division pattern and follow transient formations of cell morphological structures in their temporal and spatial behavior up to gastrulation. CONCLUSIONS Correspondences to the early cleavage pattern of other Cladocera suggest that the described pattern can be assumed to be ancestral for either the entire Cladocera or for the majority of the Cladocera comprising Anomopoda, Ctenopoda and Onychopoda. The comparison to the cell division patterns of other crustacean groups such as Malacostraca, Ostracoda, and Copepoda reveals similarities that allow for a discussion of a common pattern for the crustacean groups and a ground pattern for the Tetraconata.
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Affiliation(s)
- Frederike Alwes
- Humboldt-Universität zu Berlin, Institut für Biologie/Vergleichende Zoologie, Philippstr. 13, 10115 Berlin, Germany
- Current address: Institut de Génomique Fonctionnelle de Lyon (IGFL), 32-34 avenue Tony Garnier, Lyon 69007, France
| | - Gerhard Scholtz
- Humboldt-Universität zu Berlin, Institut für Biologie/Vergleichende Zoologie, Philippstr. 13, 10115 Berlin, Germany
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Pennerstorfer M, Scholtz G. Early cleavage in Phoronis muelleri (Phoronida) displays spiral features. Evol Dev 2013; 14:484-500. [PMID: 23134207 DOI: 10.1111/ede.12002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The view that early cleavage in Phoronida follows a radial pattern is widely accepted. However, data supporting this characterization are ambiguous. Studies have been repeatedly reporting variation between individual embryos, and the occurrence of embryos exhibiting oblique divisions or nonradial cell arrangements. Such embryos were often considered to represent variation within radial cleavage, or artificial appearances. Cleavage in Phoronis muelleri was previously characterized as "derived radial," but also oblique spindles and cell elongations, and shifted cell arrangements were observed. We studied the early cleavage in P. muelleri applying 4D microscopy, fluorescent staining, and confocal laser scanning microscopy. To deal with the problem of variation we provide statistical evaluations of our data. These show that oblique divisions do not represent variational abnormalities. In fact, they reveal that most cells divide obliquely from the third cleavage onwards. What is more, in almost all cells the axis of the third cleavage is inclined dextrally. The fourth cleavage is even stronger sinistrally pronounced. Subsequently, the pattern of alternating cleavage orientation is largely restricted to animal and vegetal blastomeres. As a result of the obliqueness of divisions, four cells encircle the poles in most embryos. Cross furrows are occasionally present. We found no indications for radial cleavage in P. muelleri. In contrast, the observed cleavage displays several characters consistent with the pattern of spiral cleavage. A close relation of phoronid and spiralian cleavage is also suggested by molecular phylogenies, allying both groups in the Lophotrochozoa. We suggest our findings to represent morphological support for this lophotrochozoan/spiralian affinity of Phoronida.
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Affiliation(s)
- Markus Pennerstorfer
- Institut für Biologie, Vergleichende Zoologie, Humboldt-Universität zu Berlin, Philippstr. 13, 10115, Berlin, Germany
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11
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Martín-Durán JM, Janssen R, Wennberg S, Budd GE, Hejnol A. Deuterostomic development in the protostome Priapulus caudatus. Curr Biol 2012; 22:2161-6. [PMID: 23103190 DOI: 10.1016/j.cub.2012.09.037] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Revised: 09/02/2012] [Accepted: 09/18/2012] [Indexed: 01/18/2023]
Abstract
The fate of the blastopore during development in the bilaterian ancestor is currently not well understood. In deuterostomes, the blastopore forms the anus, but its fate in protostome groups is variable. This variability, combined with an absence of information from key taxa, hampers the reconstruction of the ancestral developmental mode of the Protostomia and the Bilateria. The blastopore fate of the bilaterian ancestor plays a crucial role in understanding the transition from radial to bilateral symmetric organisms. Priapulids have a conservative morphology, an abundant Cambrian fossil record, and a phylogenetic position that make them a key group in understanding protostome evolution. Here, we characterize gastrulation and the embryonic expression of genes involved in bilaterian foregut and hindgut patterning in Priapulus caudatus. We show that the blastopore gives rise to the anus at the vegetal pole and that the hindgut markers brachyury and caudal are expressed in the blastopore and anus, whereas the foregut markers foxA and goosecoid are expressed in the mouth in the animal hemisphere. Thereby, gastrulation in the conservatively evolving protostome P. caudatus follows strictly a deuterostomic pattern. These results are more compatible with a deuterostomic rather than protostomic (blastopore forms the mouth) or amphistomic (mouth and anus are formed simultaneously) mode of development in the last common bilaterian ancestor.
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Affiliation(s)
- José M Martín-Durán
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen 5008, Norway
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Brenneis G, Arango CP, Scholtz G. Morphogenesis of Pseudopallene sp. (Pycnogonida, Callipallenidae) II: postembryonic development. Dev Genes Evol 2011; 221:329-50. [DOI: 10.1007/s00427-011-0381-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 11/08/2011] [Indexed: 12/22/2022]
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13
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Morphogenesis of Pseudopallene sp. (Pycnogonida, Callipallenidae) I: embryonic development. Dev Genes Evol 2011; 221:309-28. [DOI: 10.1007/s00427-011-0382-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 11/08/2011] [Indexed: 12/20/2022]
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Machner J, Scholtz G. A scanning electron microscopy study of the embryonic development of Pycnogonum litorale (Arthropoda, Pycnogonida). J Morphol 2010; 271:1306-18. [DOI: 10.1002/jmor.10871] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Laumann M, Bergmann P, Norton RA, Heethoff M. First cleavages, preblastula and blastula in the parthenogenetic mite Archegozetes longisetosus (Acari, Oribatida) indicate holoblastic rather than superficial cleavage. ARTHROPOD STRUCTURE & DEVELOPMENT 2010; 39:276-286. [PMID: 20153841 DOI: 10.1016/j.asd.2010.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 02/02/2010] [Accepted: 02/05/2010] [Indexed: 05/28/2023]
Abstract
The mode of cleavage in the Acari is generalized as superficial or intralecithal, with a preceding phase of total (holoblastic) cleavage, but the knowledge is fragmentary and conclusions have been inconsistent, even when relating to the same species. Since no data about early embryology is available for the speciose group Oribatida, we studied Archegozetes longisetosus using transmission electron microscopy. We focused on early cleavages and the formation of the blastula, as these are the important and controversial points in early embryology of the Acari. We expected, as postulated for other acarine eggs, the early cleavages to be holoblastic and followed by a superficial preblastoderm stage. The early cleavages of A. longisetosus are holoblastic and blastomeres give rise to yolk-free micromeres and macromeres containing all the yolk. In contrast to expectations, the micromeres do not form a superficial preblastoderm layer. They are scattered along the embryonic surface and form an external, monocellular layer that covers the whole surface of the embryo. Since each of the existing TEM studies of mites shows this same pattern, and since this specialized form of total cleavage seems to be unique in Chelicerata, it may be the general mode of cleavage in Acari. However, the question will require much more investigation, especially since most data relate to the Actinotrichida and very few are currently available for species in the other major group, the Anactinotrichida.
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Affiliation(s)
- Michael Laumann
- University of Tübingen, Department of Evolutionary Biology of Invertebrates, Auf der Morgenstelle 28E, 72076 Tübingen, Germany.
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