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Ordoñez JF, Wollesen T. Unfolding the ventral nerve center of chaetognaths. Neural Dev 2024; 19:5. [PMID: 38720353 PMCID: PMC11078758 DOI: 10.1186/s13064-024-00182-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 04/17/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND Chaetognaths are a clade of marine worm-like invertebrates with a heavily debated phylogenetic position. Their nervous system superficially resembles the protostome type, however, knowledge regarding the molecular processes involved in neurogenesis is lacking. To better understand these processes, we examined the expression profiles of marker genes involved in bilaterian neurogenesis during post-embryonic stages of Spadella cephaloptera. We also investigated whether the transcription factor encoding genes involved in neural patterning are regionally expressed in a staggered fashion along the mediolateral axis of the nerve cord as it has been previously demonstrated in selected vertebrate, insect, and annelid models. METHODS The expression patterns of genes involved in neural differentiation (elav), neural patterning (foxA, nkx2.2, pax6, pax3/7, and msx), and neuronal function (ChAT and VAChT) were examined in S. cephaloptera hatchlings and early juveniles using whole-mount fluorescent in situ hybridization and confocal microscopy. RESULTS The Sce-elav + profile of S. cephaloptera hatchlings reveals that, within 24 h of post-embryonic development, the developing neural territories are not limited to the regions previously ascribed to the cerebral ganglion, the ventral nerve center (VNC), and the sensory organs, but also extend to previously unreported CNS domains that likely contribute to the ventral cephalic ganglia. In general, the neural patterning genes are expressed in distinct neural subpopulations of the cerebral ganglion and the VNC in hatchlings, eventually becoming broadly expressed with reduced intensity throughout the CNS in early juveniles. Neural patterning gene expression domains are also present outside the CNS, including the digestive tract and sensory organs. ChAT and VAChT domains within the CNS are predominantly observed in specific subpopulations of the VNC territory adjacent to the ventral longitudinal muscles in hatchlings. CONCLUSIONS The observed spatial expression domains of bilaterian neural marker gene homologs in S. cephaloptera suggest evolutionarily conserved roles in neurogenesis for these genes among bilaterians. Patterning genes expressed in distinct regions of the VNC do not show a staggered medial-to-lateral expression profile directly superimposable to other bilaterian models. Only when the VNC is conceptually laterally unfolded from the longitudinal muscle into a flat structure, an expression pattern bearing resemblance to the proposed conserved bilaterian mediolateral regionalization becomes noticeable. This finding supports the idea of an ancestral mediolateral patterning of the trunk nervous system in bilaterians.
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Affiliation(s)
- June F Ordoñez
- Unit for Integrative Zoology, Department of Evolutionary Biology, University of Vienna, 1030, Vienna, Austria
| | - Tim Wollesen
- Unit for Integrative Zoology, Department of Evolutionary Biology, University of Vienna, 1030, Vienna, Austria.
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Park TYS, Nielsen ML, Parry LA, Sørensen MV, Lee M, Kihm JH, Ahn I, Park C, de Vivo G, Smith MP, Harper DAT, Nielsen AT, Vinther J. A giant stem-group chaetognath. SCIENCE ADVANCES 2024; 10:eadi6678. [PMID: 38170772 PMCID: PMC10796117 DOI: 10.1126/sciadv.adi6678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 12/01/2023] [Indexed: 01/05/2024]
Abstract
Chaetognaths, with their characteristic grasping spines, are the oldest known pelagic predators, found in the lowest Cambrian (Terreneuvian). Here, we describe a large stem chaetognath, Timorebestia koprii gen. et sp. nov., from the lower Cambrian Sirius Passet Lagerstätte, which exhibits lateral and caudal fins, a distinct head region with long antennae and a jaw apparatus similar to Amiskwia sagittiformis. Amiskwia has previously been interpreted as a total-group chaetognathiferan, as either a stem-chaetognath or gnathostomulid. We show that T. koprii shares a ventral ganglion with chaetognaths to the exclusion of other animal groups, firmly placing these fossils on the chaetognath stem. The large size (up to 30 cm) and gut contents in T. koprii suggest that early chaetognaths occupied a higher trophic position in pelagic food chains than today.
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Affiliation(s)
- Tae-Yoon S. Park
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- University of Science and Technology, 217 Gajeong-ro, Daejeon 34113, Republic of Korea
| | - Morten Lunde Nielsen
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- School of Earth Sciences, Palaeobiology Research Group, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
- British Geological Survey, Nicker Hill, Keyworth NG12 5GG, UK
| | - Luke A. Parry
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | | | - Mirinae Lee
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
| | - Ji-Hoon Kihm
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- University of Science and Technology, 217 Gajeong-ro, Daejeon 34113, Republic of Korea
| | - Inhye Ahn
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- University of Science and Technology, 217 Gajeong-ro, Daejeon 34113, Republic of Korea
| | - Changkun Park
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
| | - Giacinto de Vivo
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli, Italy
| | - M. Paul Smith
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
| | - David A. T. Harper
- Palaeoecosystems Group, Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
| | - Arne T. Nielsen
- Department of Geoscience and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, Copenhagen DK-1350, Denmark
| | - Jakob Vinther
- School of Earth Sciences, Palaeobiology Research Group, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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Kaul-Strehlow S, Urata M, Minokawa T, Stach T, Wanninger A. Neurogenesis in directly and indirectly developing enteropneusts: of nets and cords. ORG DIVERS EVOL 2015. [PMID: 26225120 PMCID: PMC4514687 DOI: 10.1007/s13127-015-0201-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Concerning the evolution of deuterostomes, enteropneusts (acorn worms) occupy a pivotal role as they share some characteristics with chordates (e.g., tunicates and vertebrates) but are also closely related to echinoderms (e.g., sea urchin). The nervous system in particular can be a highly informative organ system for evolutionary inferences, and advances in fluorescent microscopy have revealed overwhelming data sets on neurogenesis in various clades. However, immunocytochemical descriptions of neurogenesis of juvenile enteropneusts are particularly scarce, impeding the reconstruction of nervous system evolution in this group. We followed morphogenesis of the nervous system in two enteropneust species, one with direct (Saccoglossus kowalevskii) and the other with indirect development (Balanoglossus misakiensis), using an antibody against serotonin and electron microscopy. We found that all serotonin-like immunoreactive (LIR) neurons in both species are bipolar ciliary neurons that are intercalated between other epidermal cells. Unlike the tornaria larva of B. misakiensis, the embryonic nervous system of S. kowalevskii lacks serotonin-LIR neurons in the apical region as well as an opisthotroch neurite ring. Comparative analysis of both species shows that the projections of the serotonin-LIR somata initially form a basiepidermal plexus throughout the body that disappears within the trunk region soon after settlement before the concentrated dorsal and ventral neurite bundles emerge. Our data reveal a highly conserved mode of neurogenesis in enteropneusts that is independent of the developing mode and is inferred to be a common feature for Enteropneusta. Moreover, all detected serotonin-LIR neurons are presumably receptor cells, and the absence of serotonin-LIR interneurons from the enteropneust nervous system, which are otherwise common in various bilaterian central nervous systems, is interpreted as a loss that might have occurred already in the last common ancestor of Ambulacraria.
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Affiliation(s)
- Sabrina Kaul-Strehlow
- Department of Integrative Zoology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
| | - Makoto Urata
- Takehara Marine Science Station, Setouchi Field Science Center, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima 725-0024 Japan
| | - Takuya Minokawa
- Research Center for Marine Biology, Tohoku University, Asamushi, Aomori, Aomori 039-3501 Japan
| | - Thomas Stach
- Institute for Biology, Humboldt-University Berlin, Philippstr. 13, 10115 Berlin, Germany
| | - Andreas Wanninger
- Department of Integrative Zoology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
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Gasmi S, Nève G, Pech N, Tekaya S, Gilles A, Perez Y. Evolutionary history of Chaetognatha inferred from molecular and morphological data: a case study for body plan simplification. Front Zool 2014; 11:84. [PMID: 25473413 PMCID: PMC4254178 DOI: 10.1186/s12983-014-0084-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 10/30/2014] [Indexed: 11/18/2022] Open
Abstract
Background Chaetognatha are a phylum of marine carnivorous animals which includes more than 130 extant species. The internal systematics of this group have been intensively debated since it was discovered in the 18th century. While they can be traced back to the earlier Cambrian, they are an extraordinarily homogeneous phylum at the morphological level - a fascinating characteristic that puzzled many a scientist who has tried to clarify their taxonomy. Recent studies which have attempted to reconstruct a phylogeny using molecular data have relied on single gene analyses and a somewhat restricted taxon sampling. Here, we present the first large scale phylogenetic study of Chaetognatha based on a combined analysis of nearly the complete ribosomal RNA (rRNA) genes. We use this analysis to infer the evolution of some morphological characters. This work includes 36 extant species, mainly obtained from Tara Oceans Expedition 2009/2012, that represent 16 genera and 6 of the 9 extant families. Results Cladistic and phenetic analysis of morphological characters, geometric morphometrics and molecular small subunit (SSU rRNA) and large subunit (LSU rRNA) ribosomal genes phylogenies provided new insights into the relationships and the evolutionary history of Chaetognatha. We propose the following clade structure for the phylum: (((Sagittidae, Krohnittidae), Spadellidae), (Eukrohniidae, Heterokrohniidae)), with the Pterosagittidae included in the Sagittidae. The clade (Sagittidae, Krohnittidae) constitutes the monophyletic order of Aphragmophora. Molecular analyses showed that the Phragmophora are paraphyletic. The Ctenodontina/Flabellodontina and Syngonata/Chorismogonata hypotheses are invalidated on the basis of both morphological and molecular data. This new phylogeny also includes resurrected and modified genera within Sagittidae. Conclusions The distribution of some morphological characters traditionally used in systematics and for species diagnosis suggests that the diversity in Chaetognatha was produced through a process of mosaic evolution. Moreover, chaetognaths have mostly evolved by simplification of their body plan and their history shows numerous convergent events of losses and reversions. The main morphological novelty observed is the acquisition of a second pair of lateral fins in Sagittidae, which represents an adaptation to the holoplanktonic niche. Electronic supplementary material The online version of this article (doi:10.1186/s12983-014-0084-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Samah Gasmi
- Aix-Marseille Université, CNRS, IRD, Avignon Université, IMBE UMR 7263, 13331 Marseille cedex 3, France ; Université de Tunis El Manar, Faculté des Sciences de Tunis, UR11ES12 Biologie de la Reproduction et du Développement animal, 2092 El Manar, Tunis Tunisie
| | - Gabriel Nève
- Aix-Marseille Université, CNRS, IRD, Avignon Université, IMBE UMR 7263, 13331 Marseille cedex 3, France
| | - Nicolas Pech
- Aix-Marseille Université, CNRS, IRD, Avignon Université, IMBE UMR 7263, 13331 Marseille cedex 3, France
| | - Saïda Tekaya
- Université de Tunis El Manar, Faculté des Sciences de Tunis, UR11ES12 Biologie de la Reproduction et du Développement animal, 2092 El Manar, Tunis Tunisie
| | - André Gilles
- Aix-Marseille Université, CNRS, IRD, Avignon Université, IMBE UMR 7263, 13331 Marseille cedex 3, France
| | - Yvan Perez
- Aix-Marseille Université, CNRS, IRD, Avignon Université, IMBE UMR 7263, 13331 Marseille cedex 3, France
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Müller CHG, Rieger V, Perez Y, Harzsch S. Immunohistochemical and ultrastructural studies on ciliary sense organs of arrow worms (Chaetognatha). ZOOMORPHOLOGY 2013. [DOI: 10.1007/s00435-013-0211-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Perez Y, Rieger V, Martin E, Müller CHG, Harzsch S. Neurogenesis in an early protostome relative: progenitor cells in the ventral nerve center of chaetognath hatchlings are arranged in a highly organized geometrical pattern. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 320:179-93. [PMID: 23483730 DOI: 10.1002/jez.b.22493] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 12/29/2012] [Accepted: 01/23/2013] [Indexed: 01/08/2023]
Abstract
Emerging evidence suggests that Chaetognatha represent an evolutionary lineage that is the sister group to all other Protostomia thus promoting these animals as a pivotal model for our understanding of bilaterian evolutionary history. We have analyzed the proliferation of neuronal progenitor cells in the developing ventral nerve center (VNC) of Spadella cephaloptera hatchlings. To that end, for the first time in Chaetognatha, we performed in vivo incorporation experiments with the S-phase specific mitosis marker bromodeoxyuridine (BrdU). Our experiments provide evidence for a high level of mitotic activity in the VNC for ca. 3 days after hatching. Neurogenesis is carried by presumptive neuronal progenitor cells that cycle rapidly and most likely divide asymmetrically. These progenitors are arranged in a distinct grid-like geometrical pattern including about 35 transverse rows. Considering Chaetognaths to be an early offshoot of the protostome lineage we conclude that the presence of neuronal progenitor cells with asymmetric division seems to be a feature that is rooted deeply in the Metazoa. In the light of previous evidence indicating the presence of serially iterated peptidergic neurons with individual identities in the chaetognath VNC, we discuss if these neuronal progenitor cells give rise to distinct lineages. Furthermore, we evaluate the serially iterated arrangement of the progenitor cells in the light of evolution of segmentation.
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Affiliation(s)
- Yvan Perez
- Institut Méditerranéen de Biodiversité et d'Ecologie Evolution Genome Environment, IMBE-UMR CNRS 7263/IRD 237 Aix-Marseille Université/Centre St Charles, Marseille cedex 3, France
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The central and peripheral nervous system of Cephalodiscus gracilis (Pterobranchia, Deuterostomia). ZOOMORPHOLOGY 2012. [DOI: 10.1007/s00435-011-0144-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Rieger V, Perez Y, Müller CHG, Lacalli T, Hansson BS, Harzsch S. Development of the nervous system in hatchlings of Spadella cephaloptera (Chaetognatha), and implications for nervous system evolution in Bilateria. Dev Growth Differ 2011; 53:740-59. [PMID: 21671921 DOI: 10.1111/j.1440-169x.2011.01283.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Chaetognaths (arrow worms) play an important role as predators in planktonic food webs. Their phylogenetic position is unresolved, and among the numerous hypotheses, affinities to both protostomes and deuterostomes have been suggested. Many aspects of their life history, including ontogenesis, are poorly understood and, though some aspects of their embryonic and postembryonic development have been described, knowledge of early neural development is still limited. This study sets out to provide new insights into neurogenesis of newly hatched Spadella cephaloptera and their development during the following days, with attention to the two main nervous centers, the brain and the ventral nerve center. These were examined with immunohistological methods and confocal laser-scan microscopic analysis, using antibodies against tubulin, FMRFamide, and synapsin to trace the emergence of neuropils and the establishment of specific peptidergic subsystems. At hatching, the neuronal architecture of the ventral nerve center is already well established, whereas the brain and the associated vestibular ganglia are still rudimentary. The development of the brain proceeds rapidly over the next 6 days to a state that resembles the adult pattern. These data are discussed in relation to the larval life style and behaviors such as feeding. In addition, we compare the larval chaetognath nervous system and that of other bilaterian taxa in order to extract information with phylogenetic value. We conclude that larval neurogenesis in chaetognaths does not suggest an especially close relationship to either deuterostomes or protostomes, but instead displays many apomorphic features.
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Affiliation(s)
- Verena Rieger
- Zoologisches Institut und Museum, Cytologie und Evolutionsbiologie, Ernst Moritz Arndt Universität Greifswald, Soldmannstraße 23, 17487 Greifswald.
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Harzsch S, Wanninger A. Evolution of invertebrate nervous systems: the Chaetognatha as a case study. ACTA ZOOL-STOCKHOLM 2010. [DOI: 10.1111/j.1463-6395.2009.00423.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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