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Jimi N, Britayev TA, Sako M, Woo SP, Martin D. A new genus and species of nudibranch-mimicking Syllidae (Annelida, Polychaeta). Sci Rep 2024; 14:17123. [PMID: 39075131 PMCID: PMC11286968 DOI: 10.1038/s41598-024-66465-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Accepted: 07/01/2024] [Indexed: 07/31/2024] Open
Abstract
Nudibranch mollusks, which are well-known for their vivid warning coloration and effective defenses, are mimicked by diverse invertebrates to deter predation through both Müllerian and Batesian strategies. Despite extensive documentation across different taxa, mimickers have not been detected among annelids, including polychaetes, until now. This study described a new genus and species of polychaete living on Dendronephthya octocorals in Vietnam and Japan. Belonging to Syllidae, it exhibits unique morphological adaptations such as a low number of body segments, simple chaetae concealed within the parapodia and large and fusiform antennae and cirri. Moreover, these appendages are vividly colored, featuring an internal dark red area with numerous terminal white spots and bright yellow tips, effectively contributing to mimicking the appearance of a nudibranch. This discovery not only documents the first known instance of such mimicry among annelids, but also expands our understanding of evolutionary adaptation and ecological strategies in marine invertebrates.
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Affiliation(s)
- Naoto Jimi
- Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, 429-63 Sugashima, Toba, Mie, 517-0004, Japan.
- Centre for Marine & Coastal Studies, Universiti Sains Malaysia, USM, 11800, Penang, Malaysia.
| | - Temir A Britayev
- Laboratory of Marine Invertebrates Morphology and Ecology, A. N. Severtzov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russian Federation
| | - Misato Sako
- Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, 429-63 Sugashima, Toba, Mie, 517-0004, Japan
| | - Sau Pinn Woo
- Centre for Marine & Coastal Studies, Universiti Sains Malaysia, USM, 11800, Penang, Malaysia
| | - Daniel Martin
- Department of Marine Ecology, Centre d'Estudis Avançats de Blanes (CEAB-CSIC), Blanes, Catalunya, Spain
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2
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Yang X, Aguado MT, Helm C, Zhang Z, Bleidorn C. New fossil of Gaoloufangchaeta advances the origin of Errantia (Annelida) to the early Cambrian. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231580. [PMID: 38601033 PMCID: PMC11004674 DOI: 10.1098/rsos.231580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 02/27/2024] [Accepted: 02/28/2024] [Indexed: 04/12/2024]
Abstract
Molecular clock estimates suggest the origin of Annelida dates back to the Ediacaran period, which is in discordance with the first appearance of this taxon in the early Cambrian, as evidenced by the fossil records of stem-group and basally branching crown-group annelids. Using new material from the early Cambrian Guanshan biota (Cambrian Series 2, Stage 4), we re-interpret Gaoloufangchaeta bifurcus Zhao, Li & Selden, 2023, as the earliest known errantian annelid. Gaoloufangchaeta has a prominent anterior end bearing three pairs of putatively sensory appendages and a pair of anterior eyes; a muscular eversible pharynx with papillae is identified. The presence of enlarged parapodia with acicula-like structures and long capillary chaetae suggests a pelagic lifestyle for this taxon. Our phylogenetic analyses recover Gaoloufangchaeta within the Phyllodocida (Pleistoannelida, Errantia), extending the origin of Errantia back to the early Cambrian. Our data are in line with the hypothesis that Annelida diverged before the Cambrian and indicate both morphological and ecological diversification of annelids in the early Cambrian.
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Affiliation(s)
- Xiaoyu Yang
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming650500, People's Republic of China
- Animal Evolution and Biodiversity, Georg-August-Universität Göttingen, Göttingen37073, Germany
| | - M. Teresa Aguado
- Animal Evolution and Biodiversity, Georg-August-Universität Göttingen, Göttingen37073, Germany
| | - Conrad Helm
- Animal Evolution and Biodiversity, Georg-August-Universität Göttingen, Göttingen37073, Germany
| | - Zhiqian Zhang
- School of Fine Arts, Yunnan Normal University, Kunming650500, People's Republic of China
| | - Christoph Bleidorn
- Animal Evolution and Biodiversity, Georg-August-Universität Göttingen, Göttingen37073, Germany
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3
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Teixeira MAL, Fourreau CJL, Sempere-Valverde J, Carvalho S. Two new records and description of a new Perinereis (Annelida, Nereididae) species for the Saudi Arabian Red Sea region. Zookeys 2024; 1196:331-354. [PMID: 38726099 PMCID: PMC11079592 DOI: 10.3897/zookeys.1196.115260] [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: 11/05/2023] [Accepted: 01/26/2024] [Indexed: 05/12/2024] Open
Abstract
Annelid biodiversity studies in the Red Sea are limited and integrative taxonomy is needed to accurately improve reference libraries in the region. As part of the bioblitz effort in Saudi Arabia to assess the invertebrate biodiversity in the northern Red Sea and Gulf of Aqaba, Perinereis specimens from intertidal marine and lagoon-like rocky environments were selected for an independent assessment, given the known taxonomic ambiguities in this genus. This study used an integrative approach, combining molecular with morphological and geographic data. Our results demonstrate that specimens found mainly in the Gulf of Aqaba are not only morphologically different from other five similar Perinereis Group I species reported in the region, but phylogenetic analysis using available COI sequences from GenBank revealed different molecular operational taxonomic units, suggesting an undescribed species, P.kaustianasp. nov. The new species is genetically close and shares a similar paragnath pattern to the Indo-Pacific distributed P.helleri, in particular in Area III and Areas VII-VIII. Therefore, we suggest it may belong to the same species complex. However, P.kaustianasp. nov. differs from the latter mainly in the shorter length of the postero-dorsal tentacular cirri, median parapodia with much longer dorsal Tentacular cirri, posteriormost parapodia with much wider and greatly expanded dorsal ligules. Additionally, two new records are reported for the Saudi Neom area belonging to P.damietta and P.suezensis, previously described only for the Egyptian coast (Suez Canal) and are distributed sympatrically with the new species, but apparently not sympatric with each other.
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Affiliation(s)
- Marcos A. L. Teixeira
- Biological and Environmental Science and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Chloé Julie Loïs Fourreau
- Molecular Invertebrate Systematics and Ecology (MISE) Lab, Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Juan Sempere-Valverde
- Biological and Environmental Science and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
- Laboratorio de Biología Marina/Estación de Biología Marina del Estrecho (Ceuta), Departamento de Zoología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012, Sevilla, Spain
| | - Susana Carvalho
- Biological and Environmental Science and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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4
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Nakamura M, Oguchi K, Sato DS, Kato S, Okanishi M, Hayashi Y, Aguado MT, Miura T. Morphological, histological and gene-expression analyses on stolonization in the Japanese Green Syllid, Megasyllis nipponica (Annelida, Syllidae). Sci Rep 2023; 13:19419. [PMID: 37993494 PMCID: PMC10665476 DOI: 10.1038/s41598-023-46358-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 10/31/2023] [Indexed: 11/24/2023] Open
Abstract
Benthic annelids belonging to the family Syllidae (Annelida, Errantia, Phyllodocida) exhibit a unique reproduction mode called "schizogamy" or "stolonization", in which the posterior body part filled with gametes detaches from the original body, as a reproductive unit (stolon) that autonomously swims and spawns. In this study, morphological and histological observations on the developmental processes during stolonization were carried out in Megasyllis nipponica. Results suggest that the stolon formation started with maturation of gonads, followed by the formation of a head ganglion in the anteriormost segment of the developing stolon. Then, the detailed stolon-specific structures such as stolon eyes and notochaetae were formed. Furthermore, expression profiles of genes involved in the anterior-posterior identity (Hox genes), head determination, germ-line, and hormone regulation were compared between anterior and posterior body parts during the stolonization process. The results reveal that, in the posterior body part, genes for gonadal development were up-regulated, followed by hormone-related genes and head-determination genes. Unexpectedly, Hox genes known to identify body parts along the anterior-posterior axis showed no significant temporal expression changes. These findings suggest that during stolonization, gonad development induces the head formation of a stolon, without up-regulation of anterior Hox genes.
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Affiliation(s)
- Mayuko Nakamura
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa, 238-0225, Japan
| | - Kohei Oguchi
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa, 238-0225, Japan
| | - Daisuke S Sato
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa, 238-0225, Japan
| | - Sumika Kato
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa, 238-0225, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo, Tokyo, 113-0033, Japan
| | - Masanori Okanishi
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa, 238-0225, Japan
- Faculty of Human Environmental Studies, Hiroshima Shudo University, Ozuka-Higashi, Asaminami, Hiroshima, 731-3195, Japan
| | - Yoshinobu Hayashi
- Department of Biology, Keio University, Hiyoshi, Yokohama, 223-8521, Japan
| | - M Teresa Aguado
- Animal Evolution and Biodiversity, Georg-August-Universität Göttingen, 37073, Göttingen, Germany
| | - Toru Miura
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa, 238-0225, Japan.
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5
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Suzzi AL, Huggett MJ, Gaston TF, MacFarlane GR, Alam MR, Gibb J, Stat M. eDNA metabarcoding reveals shifts in sediment eukaryote communities in a metal contaminated estuary. MARINE POLLUTION BULLETIN 2023; 191:114896. [PMID: 37058833 DOI: 10.1016/j.marpolbul.2023.114896] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 03/21/2023] [Accepted: 03/27/2023] [Indexed: 05/13/2023]
Abstract
Metal contamination is a global issue impacting biodiversity in urbanised estuaries. Traditional methods to assess biodiversity are time consuming, costly and often exclude small or cryptic organisms due to difficulties with morphological identification. Metabarcoding approaches have been increasingly recognised for their utility in monitoring, however studies have focused on freshwater and marine systems despite the ecological significance of estuaries. We targeted estuarine eukaryote communities within the sediments of Australia's largest urbanised estuary, where a history of industrial activity has resulted in a metal contamination gradient. We identified specific eukaryote families with significant correlations with bioavailable metal concentrations, indicating sensitivity or tolerance to specific metals. While polychaete families Terebellidae and Syllidae demonstrated tolerance to the contamination gradient, members of the meio- and microfaunal communities including diatoms, dinoflagellates and nematodes displayed sensitivities. These may have high value as indicators but are frequently missed in traditional surveys due to sampling limitations.
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Affiliation(s)
- Alessandra L Suzzi
- School of Environmental and Life Sciences, The University of Newcastle, Ourimbah, NSW 2258, Australia.
| | - Megan J Huggett
- School of Environmental and Life Sciences, The University of Newcastle, Ourimbah, NSW 2258, Australia
| | - Troy F Gaston
- School of Environmental and Life Sciences, The University of Newcastle, Ourimbah, NSW 2258, Australia
| | - Geoff R MacFarlane
- School of Environmental and Life Sciences, The University of Newcastle, Ourimbah, NSW 2258, Australia
| | - Md Rushna Alam
- School of Environmental and Life Sciences, The University of Newcastle, Ourimbah, NSW 2258, Australia; Department of Aquaculture, Patuakhali Science and Technology University, Dumki, Patuakhali, Bangladesh
| | - Jodie Gibb
- School of Environmental and Life Sciences, The University of Newcastle, Ourimbah, NSW 2258, Australia
| | - Michael Stat
- School of Environmental and Life Sciences, The University of Newcastle, Ourimbah, NSW 2258, Australia
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6
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Revealing the diversity of the green Eulalia (Annelida, Phyllodocidae) species complex along the European coast, with description of three new species. ORG DIVERS EVOL 2023. [DOI: 10.1007/s13127-022-00597-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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7
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Hayashi Y, Oguchi K, Nakamura M, Koshikawa S, Miura T. Construction of a massive genetic resource by transcriptome sequencing and genetic characterization of Megasyllis nipponica (Annelida: Syllidae). Genes Genet Syst 2022; 97:153-166. [PMID: 36070927 DOI: 10.1266/ggs.21-00137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Understanding the processes and consequences of the morphological diversity of organisms is one of the major goals of evolutionary biology. Studies on the evolution of developmental mechanisms of morphologies, or evo-devo, have been extensively conducted in many taxa and have revealed many interesting phenomena at the molecular level. However, many other taxa exhibiting intriguing morphological diversity remain unexplored in the field of evo-devo. Although the annelid family Syllidae shows spectacular diversity in morphological development associated with reproduction, its evo-devo study, especially on molecular development, has progressed slowly. In this study, we focused on Megasyllis nipponica as a new model species for evo-devo in syllids and performed transcriptome sequencing to develop a massive genetic resource, which will be useful for future molecular studies. From the transcriptome data, we identified candidate genes that are likely involved in morphogenesis, including genes involved in hormone regulation, sex determination and appendage development. Furthermore, a computational analysis of the transcriptome sequence data indicated the occurrence of DNA methylation in coding regions of the M. nipponica genome. In addition, flow cytometry analysis showed that the genome size of M. nipponica was approximately 524 megabases. These results facilitate the study of morphogenesis in molecular terms and contribute to our understanding of the morphological diversity in syllids.
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Affiliation(s)
| | - Kohei Oguchi
- Misaki Marine Biological Station, School of Science, The University of Tokyo.,National Institute of Advanced Industrial Science and Technology (AIST)
| | - Mayuko Nakamura
- Misaki Marine Biological Station, School of Science, The University of Tokyo
| | - Shigeyuki Koshikawa
- Faculty of Environmental Earth Science, Hokkaido University.,Graduate School of Environmental Science, Hokkaido University
| | - Toru Miura
- Misaki Marine Biological Station, School of Science, The University of Tokyo
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8
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OUP accepted manuscript. Zool J Linn Soc 2022. [DOI: 10.1093/zoolinnean/zlac046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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9
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Are well-studied marine biodiversity hotspots still blackspots for animal barcoding? Glob Ecol Conserv 2021. [DOI: 10.1016/j.gecco.2021.e01909] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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10
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Tilic E, Stiller J, Campos E, Pleijel F, Rouse GW. Phylogenomics resolves ambiguous relationships within Aciculata (Errantia, Annelida). Mol Phylogenet Evol 2021; 166:107339. [PMID: 34751138 DOI: 10.1016/j.ympev.2021.107339] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 10/23/2021] [Accepted: 10/27/2021] [Indexed: 10/20/2022]
Abstract
Aciculata (Eunicida + Phyllodocida) is among the largest clades of annelids, comprising almost half of the known diversity of all marine annelids. Despite the group's large size and biological importance, most phylogenomic studies on Annelida to date have had a limited sampling of this clade. The phylogenetic placement of many clades within Phyllodocida in particular has remained poorly understood. To resolve the relationships within Aciculata we conducted a large-scale phylogenomic analysis based on 24 transcriptomes (13 new), chosen to represent many family-ranked taxa that have never been included in a broad phylogenomic study. Our sampling also includes several enigmatic taxa with challenging phylogenetic placement, such as Histriobdella, Struwela, Lacydonia, Pilargis and the holopelagic worms Lopadorrhynchus, Travisiopsis and Tomopteris. Our robust phylogeny allows us to name and place some of these problematic clades and has significant implications on the systematics of the group. Within Eunicida we reinstate the names Eunicoidea and Oenonoidea. Within Phyllodocida we delineate Phyllodociformia, Glyceriformia, Nereidiformia, Nephtyiformia and Aphroditiformia. Phyllodociformia now includes: Lacydonia, Typhloscolecidae, Lopadorrhynchidae and Phyllodocidae. Nephtyiformia includes Nephtyidae and Pilargidae. We also broaden the delineation of Glyceriformia to include Sphaerodoridae, Tomopteridae and Glyceroidea (Glyceridae + Goniadidae). Furthermore, our study demonstrates and explores how conflicting, yet highly supported topologies can result from confounding signals in gene trees.
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Affiliation(s)
- Ekin Tilic
- Scripps Institution of Oceanography, UC San Diego, La Jolla, CA, USA; Institute of Evolutionary Biology and Animal Ecology, University of Bonn, Germany; Marine Biological Section, Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark.
| | - Josefin Stiller
- Centre for Biodiversity Genomics, Section for Ecology and Evolution, Department of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Ernesto Campos
- Facultad de Ciencias, Universidad Autónoma de Baja California. Ensenada, Baja California, México
| | - Fredrik Pleijel
- Department of Marine Sciences, University of Gothenburg, Tjärnö, Sweden
| | - Greg W Rouse
- Scripps Institution of Oceanography, UC San Diego, La Jolla, CA, USA.
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11
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Nascimento RL, Fukuda MV, Paresque K, Nogueira JMDM, de Paiva PC. A synopsis of Salvatoria McIntosh, 1885 (Annelida: Syllidae: Exogoninae) from Brazilian coastal and oceanic waters. PLoS One 2021; 16:e0250472. [PMID: 33951079 PMCID: PMC8099080 DOI: 10.1371/journal.pone.0250472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 04/07/2021] [Indexed: 11/19/2022] Open
Abstract
We compiled the records for the genus Salvatoria from Brazilian coastal and oceanic habitats, collected by several projects along the years. Here we present 12 species, eight of which already reported-S. breviarticulata comb. nov., S. clavata, S. euritmica, S. heterocirra, S. limbata, S. longiarticulata comb. nov., S. neapolitana and S. cf. nitidula-with comments regarding the confidence of some of these records. We also describe three new species, S. marielleae n. sp. and Salvatoria nitiduloides n. sp., based on material from Fernando de Noronha and Trindade islands, off the Northeastern Brazilian coast, and S. ypsiloides n. sp., from Fernando de Noronha and also, Campos Basin, off Southeastern Brazilian coast, in depths down to 970 m. Finally, we report a probably undescribed species, Salvatoria sp., represented by only one specimen lacking median antenna, preventing us to proceed with further identification properly. A dichotomous identification key and a comparative table with morphological data of specimens belonging to these species are also provided.
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Affiliation(s)
- Rodolfo Leandro Nascimento
- Laboratório de Polychaeta, Departamento de Zoologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
- Programa de Pós–graduação em Biodiversidade e Biologia Evolutiva, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Karla Paresque
- Laboratório de Bentologia, Instituto de Ciências Biológicas e da Saúde, Universidade Federal de Alagoas, Maceió, Alagoas, Brazil
| | - João Miguel de Matos Nogueira
- Laboratório de Poliquetologia (LaPol), Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Paulo Cesar de Paiva
- Laboratório de Polychaeta, Departamento de Zoologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
- Programa de Pós–graduação em Biodiversidade e Biologia Evolutiva, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
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12
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Ponz-Segrelles G, Glasby CJ, Helm C, Beckers P, Hammel JU, Ribeiro RP, Aguado MT. Integrative anatomical study of the branched annelid Ramisyllis multicaudata (Annelida, Syllidae). J Morphol 2021; 282:900-916. [PMID: 33813762 DOI: 10.1002/jmor.21356] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/26/2021] [Accepted: 03/30/2021] [Indexed: 01/14/2023]
Abstract
The sponge-dwelling Syllidae Ramisyllis multicaudata and Syllis ramosa are the only annelid species for which a branched body with one head and multiple posterior ends is known. In these species, the head is located deep within the sponge, and the branches extend through the canal system of their host. The morphology of these creatures has captivated annelid biologists since they were first discovered in the late XIXth century, and their external characteristics have been well documented. However, how their branched bodies fit within their symbiotic host sponges and how branches translate into internal anatomy has not been documented before. These features are crucially relevant for understanding the body of these animals, and therefore, the aim of this study was to investigate these aspects. In order to assess these questions, live observation, as wells as histology, immunohistochemistry, micro-computed tomography, and transmission electron microscopy techniques were used on specimens of R. multicaudata. By using these techniques, we show that the complex body of R. multicaudata specimens extends greatly through the canal system of their host sponges. We demonstrate that iterative external bifurcation of the body is accompanied by the bifurcation of the longitudinal organ systems that are characteristic of annelids. Additionally, we also highlight that the bifurcation process leaves an unmistakable fingerprint in the form of newly-described "muscle bridges." These structures theoretically allow one to distinguish original and derived branches at each bifurcation. Last, we characterize some of the internal anatomical features of the stolons (reproductive units) of R. multicaudata, particularly their nervous system. Here, we provide the first study of the internal anatomy of a branched annelid. This information is not only crucial to deepen our understanding of these animals and their biology, but it will also be key to inform future studies that try to explain how this morphology evolved.
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Affiliation(s)
| | - Christopher J Glasby
- Natural Sciences Department, Museum and Art Gallery of the Northern Territory, Darwin, Northern Territory, Australia
| | - Conrad Helm
- Animal Evolution & Biodiversity, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Patrick Beckers
- Institute of Evolutionary Biology and Ecology, University of Bonn, Bonn, Germany
| | - Jörg U Hammel
- Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
| | - Rannyele P Ribeiro
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - M Teresa Aguado
- Animal Evolution & Biodiversity, Georg-August-Universität Göttingen, Göttingen, Germany
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13
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Abstract
Annelida is a ubiquitous, common and diverse group of organisms, found in terrestrial, fresh waters and marine environments. Despite the large efforts put into resolving the evolutionary relationships of these and other Lophotrochozoa, and the delineation of the basal nodes within the group, these are still unanswered. Annelida holds an enormous diversity of forms and biological strategies alongside a large number of species, following Arthropoda, Mollusca, Vertebrata and perhaps Platyhelminthes, among the species most rich in phyla within Metazoa. The number of currently accepted annelid species changes rapidly when taxonomic groups are revised due to synonymies and descriptions of a new species. The group is also experiencing a recent increase in species numbers as a consequence of the use of molecular taxonomy methods, which allows the delineation of the entities within species complexes. This review aims at succinctly reviewing the state-of-the-art of annelid diversity and summarizing the main systematic revisions carried out in the group. Moreover, it should be considered as the introduction to the papers that form this Special Issue on Systematics and Biodiversity of Annelids.
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