Distribution of Tenagodus modestus (Dall, 1881) (Mollusca, Siliquariidae) along the northern coast of Brazil: New records and biogeographical notes

Distribution of Tenagodus modestus (Dall, 1881) (Mollusca, Siliquariidae) along the northern coast of Brazil: New records and biogeographical notes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Distribution of Tenagodus modestus (Dall, 1881) (Mollusca, Siliquariidae) along the northern coast of Brazil: New records and biogeographical notes Jésus Adriano Silva, Adriana Melo, Smith Ogawa, Ana Patricia Cordeiro, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8919989/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 9 You are reading this latest preprint version Abstract This study presents new records of the marine gastropod Tenagodus modestus (Dall, 1881 ), a representative of the Siliquariidae family, for the northern coast of Brazil, an extensive and highly biologically productive area composed of an Amazonian Reef System. The aim of this study is to present new occurrences of the gastropod T. modestus on the North Coast of Brazil and to update the species' distribution along the Brazilian coast. The records were reported based on a review of scientific literature, museum databases, and an expedition carried out during the 1st Amazonian Corals Expedition conducted by the Centro Nacional de Pesquisa e Conservação da Biodiversidade Marinha do Norte - CEPNOR/ICMBio, between March 7 and 14, 2025, aboard the research vessel Soloncy Moura. In total, numerous records were made for the region, indicating that the species is present and contributes to the local biodiversity, and not an occasional occurrence. Thus, we confirm the occurrence of the species on the northern coast of Brazil and indicate an increase in its distribution along the Brazilian coast from Amapá to Espírito Santo. Biogeography Amazon Continental Shelf Siliquariidae Figures Figure 1 Figure 2 Figure 3 INTRODUCTION The continental shelf of northern Brazil is extensive and highly biologically productive, comprising a Amazonian Reef System, a complex consolidated bottom environment formed by living organisms (Collette and Ruetzler, 1977; Caires, 2021). The most recent records indicate 3,286 species on the Amazonian Continental Shelf, with 472 species belonging to five classes of mollusks (bivalves, gastropods, cephalopods, polyplacophorans, and scaphopods) that are generally impacted by anthropogenic actions, such as fishing practices in the region (Klautau et al., 2025 ). Among marine gastropod mollusks, members of the family Siliquariidae are known worldwide as "snail worms" due to the spiral shape of their shells (Bieler, 1990 ; Rios, 2009 ). In total, three species of the genus Tenagodus Guettard, 1770 are known in the Western Atlantic Ocean: Tenagodus modestus (Dall, 1881 ), Tenagodus squamatus (Blainville, 1827), and Tenagodus barbadensis Bieler, 2004 (Bieler, 2004 ). These gastropods are rarely target species in research, with their records mainly occurring in studies of the composition of benthic fauna (Bieler, 1990 ). Siliquariids are reclusive creatures, living in subterranean habitats, generally associated with sponges (Bieler, 1990 , 2004 ; Pansini, Cattaneo-Vietti, & Schiaparelli, 1999). Bieler ( 2004 ) carried out a systematic review of the members of the genus Tenagodus in the Western Atlantic and provided the first detailed functional morphological study of Tenagodus modestus (Dall, 1881 ). The gastropod has a whitish coloration, with some individuals varying in light brown tones (Dall, 1981). Its vision is limited, so it feeds on suspended detritus and has restricted mobility (stationary), which causes it to reach high densities (5,400 individuals/m 2 ) (Bieler, 2004 ). They generally occur at depths of 18 to 1,472 meters (Dall, 1881 ) and have recently been found in the intertidal zone (Chagas et al, 2025). Its distribution is estimated in the Western Atlantic Ocean, from Bermuda, Florida, the Gulf of Mexico, the Caribbean Sea and the Bahamas to Brazil (Rios, 2009 ; Rosenberg, 2009 ). In Brazil, it has only confirmed records from Bahia to Espírito Santo and in the North region of Brazil, where there is an occasional report in 1975 (GBIF, 2025). Thus, the present study aims to present new occurrences of the gastropod Tenagodus modestus on the northern coast of Brazil and to update the distribution of the species along the Brazilian coast. MATERIALS AND METHODS Study area The collections were carried out on the northern coast of Brazil. The area is characterized by Caires et al. ( 2021 ) as the region between the mouth of the Oiapoque River, which marks the border between Brazil and French Guiana, and the mouth of the Parnaíba River, which marks the border between the states of Maranhão and Piauí, where the Amazonian and Piauí/Maranhão sedimentary basins are located, extending for more than 2,500 km. According to the same authors, this region can be divided into three sectors: (1) the coast of Amapá, with a straight coastline and a continental shelf dominated by hard, rocky substrates; (2) the coast of Pará, with a deeply indented coastline and a continental shelf dominated by predominantly muddy substrates; and (3) the coast of Maranhão, with its jagged coastline extending to Tubarão Bay, but becoming straight between Cabo Gurupi and the Parnaíba River, and the continental shelf formed by substrates with a mixture of mud and sand. Sampling procedure During benthos sampling, two trawl dredges were collected at 12 sampling points. Each dredge was towed for 4 minutes, at depths ranging from 75 m to 164 m. After each trawl, the sampled material was placed on the ship's deck for preliminary sorting (Fig. 1 ), where organisms were separated/extracted from the sediment/rocks, coded, and fixed in 70% alcohol. After landing, the samples were sent to the Biodiversity Conservation Laboratory, linked to CEPNOR/ICMBio, for taxonomic identification according to specialized literature. Subsequently, the individuals were deposited in the Malacological Collection of the Zoology Museum of UFRA, under voucher MZUFRA Moll1488. In order to update the species' distribution limits in the region, records of its occurrence in the scientific literature on the CAPES Periodicals Portal and in databases of institutions and museums available on the Global Biodiversity Information Facility (GBIF) ( https://www.gbif.org/ ), Ocean Biodiversity Information System (OBIS) ( https://obis.org/ ), Taxonomic Catalog of the Fauna of Brazil (CTFB) ( http://fauna.jbrj.gov.br ) and on the speciesLink network ( http://www.splink.org.br/ ) were investigated. The search was conducted between November and December 2024, and the terms used to filter the articles were (“ Tenagodus modestus ” “ Tenagodus ” OR Siliquariidae OR “worm-snails” OR “Slit wormsnail”). Furthermore, records of gastropod mollusks listed and reported by the CEPNOR, which conducts continuous monitoring of marine biodiversity on the Amazon Continental Shelf, were consulted. RESULTS AND DISCUSSION The three specimens found during the scientific expedition were associated with corals (Fig. 2 A) and rhodoliths (Fig. 2 B), which contradicts what was indicated by Bieler ( 1990 ), who found the species generally associated with sponges as a substrate for attachment. The individuals found are between 60 and 80 mm long, which is consistent with previously recorded animals that generally had a total length of less than 80 mm. Even so, they are considered relatively large individuals and can reach up to 150 mm in length (Bieler, 2004 ; Rosenberg, 2009 ). A review of the literature and databases revealed other occurrences of the species in the region. The first record, in GBIF, was in 1975; 3 records from the CEPNOR report the mollusk as bycatch in snapper fishing in 2023; and, more recently, Chagas et al. (2025) described its occurrence in 2020 in the intertidal zone, in a mangrove area located in the estuary of the Primavera River, on the Amazon coast (Fig. 3 ). This study presents the species in a new area on the northern coast of Brazil, where it is found associated with coral reefs and rhodoliths (calcareous rocks). Based on these records, the presence of the species in the region is confirmed, and an increase in its biogeography along the Brazilian coast is indicated, beyond that estimated by Chagas et al. (2025) in the intertidal zone off the coast of the state of Pará. CONCLUSIONS Thus, the biogeographical expansion of Tenagodus modestus in the Northern Region of Brazil, from the state of Amapá to the coast of the state of0 Espírito Santo. This study contributes to further research on the benthic biodiversity present on the Amazonian continental shelf. Declarations Conflict of Interest The authors declare no conflict of interest. Acknowledgements We thank Centro Nacional de Pesquisa e Conservação da Biodiversidade Marinha do Norte CEPNOR/ICMBio) and crew of the research vessel Soloncy Moura. Author Contributions J.A.S.S. and A.C.M. wrote the main text of the manuscript. All authors (S.S.O., A.P.B.C., W.C.R.S., M.R.F.B., R.A.C. and A.G.C.M.K.) reviewed and approved the final version of the manuscript. Funding The authors did not receive support from any organization for the submitted work. Data Availability All data generated or analysed during this study are included in this published article. References Bieler R (1990) Sessile slit-shells–a first look at Tenagodus anatomy and biology (Cerithioidea: Siliquariidae). Western Society of Malacologists Annual Report , 22 , 21–22 Bieler R (2004) Sanitation with sponge and plunger: western Atlantic slit-wormsnails (Mollusca: Caenogastropoda: Siliquariidae). Zool J Linn Soc 140(3):307–333 Caires RA, Carvalho-Filho A, Rotundo MM, Santos WC, R. D, Klautau AG (2021) C. M. Peixes teleósteos da costa norte do Brasil . A. P. Marceniuk (Ed.). Museu Paraense Emílio Goeldi Collette BB, Rützler K (1977) Peixes de recife sobre fundos de esponjas na foz do rio Amazonas Dall WH (1881) Relatórios sobre os resultados da dragagem, sob a supervisão de Alexander Agassiz, no Golfo do México e no Mar do Caribe, 1877-79, pelo navio a vapor Blake do Serviço Geológico da Costa dos EUA. 15. Relatório preliminar sobre os moluscos. Bol do Museu de Zoologia Comparada do Harv Coll 9:33–144 de Klautau M, Cordeiro AGC, das Chagas APB, Dos Santos RA, Marceniuk WCR, da Nóbrega AP, Bentes PSV, B (2025) Hotspots de biodiversidade e espécies ameaçadas sob influência humana na plataforma continental amazônica. Relatórios Científicos 15(1):26681 GBIF Secretariat. Tenagodus modestus (Dall, 1881). GBIF Backbone Taxonomy (2025) Checklist dataset. Available at: https://doi.org/10.15468/39omei Accessed at: 2025, November 18 Pansini M, Cattaneo-Vietti R, Sehiaparelli S (1999) Relationship between sponges and a taxon of obligatory inquilines: the siliquariid molluscs. Memoirs of the Queensland Museum, Nature, 44, 427–438 Rios EDC (2009) Compendium of Brazilian sea shells. Editora Evangraf Rosenberg G (2009) Malacolog 4.1.1: A Database of Western Atlantic Marine Mollusca. at: http://www.malacolog.org . Acesso em: 18/03/2020 Accessed at: November 18, 2025 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 16 Mar, 2026 Reviews received at journal 16 Mar, 2026 Reviews received at journal 16 Mar, 2026 Reviewers agreed at journal 12 Mar, 2026 Reviewers agreed at journal 07 Mar, 2026 Reviewers invited by journal 04 Mar, 2026 Editor assigned by journal 04 Mar, 2026 Submission checks completed at journal 04 Mar, 2026 First submitted to journal 19 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8919989","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":602308518,"identity":"bf42405f-6469-4b75-a596-27ef1998b1b5","order_by":0,"name":"Jésus Adriano Silva","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYJACAxDBxg4kPsAYxGlhZmBgnAFlEAmAKpl5oAy8gF+6/ULBhz+H7fmYeQw/2/zaJs/HzMD44WMObi2Sc84UGM5sO5zYxsxjLJ3bd9uwjZmBWXLmNjz+uJGTYMzbcDiBjZktQTq35zYjUAsbMy8eLfYgLX+ADgNqSf5t2XPbnqAWA4n0A8YMbIeBhjMfk2b4cTuRoBaJGzkMhr1t6YkgLZa9DbeT25gZm/H6hX9G+jODH3+s7eXbG5tv/Phz23Z+e/PBDx/xaGFg4DEzgLMZ28BkAz71QMD++AGC84eA4lEwCkbBKBiRAAAk2kuK3yeZwwAAAABJRU5ErkJggg==","orcid":"","institution":"Centro Nacional de Pesquisa e Conservação da Biodiversidade Marinha do Norte - CEPNOR/ICMBio. 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Belém","correspondingAuthor":false,"prefix":"","firstName":"Rafael","middleName":"das","lastName":"Chagas","suffix":""},{"id":602308528,"identity":"c1b016cf-f4cb-4763-9177-7fa7e831955a","order_by":7,"name":"Alex Klautau","email":"","orcid":"","institution":"Centro Nacional de Pesquisa e Conservação da Biodiversidade Marinha do Norte - CEPNOR/ICMBio. Belém","correspondingAuthor":false,"prefix":"","firstName":"Alex","middleName":"","lastName":"Klautau","suffix":""}],"badges":[],"createdAt":"2026-02-19 18:08:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8919989/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8919989/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104248684,"identity":"62c374e3-8153-4f7e-aefc-f542c4381d03","added_by":"auto","created_at":"2026-03-09 15:46:49","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":734330,"visible":true,"origin":"","legend":"\u003cp\u003eSediments collected with the aid of a dredge on the deck of the research vessel Soloncy Moura.\u003c/p\u003e","description":"","filename":"image1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8919989/v1/10348c1392aff1ea3f7b3d90.jpeg"},{"id":104248683,"identity":"8cd4e6fc-e581-4d22-bd68-1607f85ff97e","added_by":"auto","created_at":"2026-03-09 15:46:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":531334,"visible":true,"origin":"","legend":"\u003cp\u003eTenagodus modestus associated with corals found on the Amazonian continental shelf during a CEPNOR scientific expedition. A: associated with corals. B: associated with limestone rocks.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-8919989/v1/13f64e576f9d6d22c85601b4.png"},{"id":104405137,"identity":"5ed122b9-cb1a-4101-ada7-40fe501e5c65","added_by":"auto","created_at":"2026-03-11 12:21:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":857159,"visible":true,"origin":"","legend":"\u003cp\u003eMap of Tenagodus modestus recording points on the Brazilian North Coast.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-8919989/v1/bcdc949bb61cd7976397c54d.png"},{"id":104410862,"identity":"bb0f5783-8751-4564-a730-d23af588ee9b","added_by":"auto","created_at":"2026-03-11 12:54:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2638548,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8919989/v1/1a405064-7093-48fc-8351-4ec633d1ec8e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Distribution of Tenagodus modestus (Dall, 1881) (Mollusca, Siliquariidae) along the northern coast of Brazil: New records and biogeographical notes","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe continental shelf of northern Brazil is extensive and highly biologically productive, comprising a Amazonian Reef System, a complex consolidated bottom environment formed by living organisms (Collette and Ruetzler, 1977; Caires, 2021). The most recent records indicate 3,286 species on the Amazonian Continental Shelf, with 472 species belonging to five classes of mollusks (bivalves, gastropods, cephalopods, polyplacophorans, and scaphopods) that are generally impacted by anthropogenic actions, such as fishing practices in the region (Klautau et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAmong marine gastropod mollusks, members of the family Siliquariidae are known worldwide as \"snail worms\" due to the spiral shape of their shells (Bieler, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Rios, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). In total, three species of the genus \u003cem\u003eTenagodus\u003c/em\u003e Guettard, 1770 are known in the Western Atlantic Ocean: \u003cem\u003eTenagodus modestus\u003c/em\u003e (Dall, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1881\u003c/span\u003e), \u003cem\u003eTenagodus squamatus\u003c/em\u003e (Blainville, 1827), and \u003cem\u003eTenagodus barbadensis\u003c/em\u003e Bieler, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2004\u003c/span\u003e (Bieler, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). These gastropods are rarely target species in research, with their records mainly occurring in studies of the composition of benthic fauna (Bieler, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). Siliquariids are reclusive creatures, living in subterranean habitats, generally associated with sponges (Bieler, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1990\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Pansini, Cattaneo-Vietti, \u0026amp; Schiaparelli, 1999).\u003c/p\u003e \u003cp\u003eBieler (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) carried out a systematic review of the members of the genus \u003cem\u003eTenagodus\u003c/em\u003e in the Western Atlantic and provided the first detailed functional morphological study of \u003cem\u003eTenagodus modestus\u003c/em\u003e (Dall, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1881\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe gastropod has a whitish coloration, with some individuals varying in light brown tones (Dall, 1981). Its vision is limited, so it feeds on suspended detritus and has restricted mobility (stationary), which causes it to reach high densities (5,400 individuals/m\u003csup\u003e2\u003c/sup\u003e) (Bieler, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). They generally occur at depths of 18 to 1,472 meters (Dall, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1881\u003c/span\u003e) and have recently been found in the intertidal zone (Chagas et al, 2025).\u003c/p\u003e \u003cp\u003eIts distribution is estimated in the Western Atlantic Ocean, from Bermuda, Florida, the Gulf of Mexico, the Caribbean Sea and the Bahamas to Brazil (Rios, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Rosenberg, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). In Brazil, it has only confirmed records from Bahia to Esp\u0026iacute;rito Santo and in the North region of Brazil, where there is an occasional report in 1975 (GBIF, 2025).\u003c/p\u003e \u003cp\u003eThus, the present study aims to present new occurrences of the gastropod \u003cem\u003eTenagodus modestus\u003c/em\u003e on the northern coast of Brazil and to update the distribution of the species along the Brazilian coast.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cp\u003eStudy area\u003c/p\u003e \u003cp\u003eThe collections were carried out on the northern coast of Brazil. The area is characterized by Caires et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) as the region between the mouth of the Oiapoque River, which marks the border between Brazil and French Guiana, and the mouth of the Parna\u0026iacute;ba River, which marks the border between the states of Maranh\u0026atilde;o and Piau\u0026iacute;, where the Amazonian and Piau\u0026iacute;/Maranh\u0026atilde;o sedimentary basins are located, extending for more than 2,500 km. According to the same authors, this region can be divided into three sectors: (1) the coast of Amap\u0026aacute;, with a straight coastline and a continental shelf dominated by hard, rocky substrates; (2) the coast of Par\u0026aacute;, with a deeply indented coastline and a continental shelf dominated by predominantly muddy substrates; and (3) the coast of Maranh\u0026atilde;o, with its jagged coastline extending to Tubar\u0026atilde;o Bay, but becoming straight between Cabo Gurupi and the Parna\u0026iacute;ba River, and the continental shelf formed by substrates with a mixture of mud and sand.\u003c/p\u003e \u003cp\u003eSampling procedure\u003c/p\u003e \u003cp\u003eDuring benthos sampling, two trawl dredges were collected at 12 sampling points. Each dredge was towed for 4 minutes, at depths ranging from 75 m to 164 m. After each trawl, the sampled material was placed on the ship's deck for preliminary sorting (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), where organisms were separated/extracted from the sediment/rocks, coded, and fixed in 70% alcohol. After landing, the samples were sent to the Biodiversity Conservation Laboratory, linked to CEPNOR/ICMBio, for taxonomic identification according to specialized literature. Subsequently, the individuals were deposited in the Malacological Collection of the Zoology Museum of UFRA, under voucher MZUFRA Moll1488.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn order to update the species' distribution limits in the region, records of its occurrence in the scientific literature on the CAPES Periodicals Portal and in databases of institutions and museums available on the Global Biodiversity Information Facility (GBIF) (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.gbif.org/\u003c/span\u003e\u003cspan address=\"https://www.gbif.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e), Ocean Biodiversity Information System (OBIS) (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://obis.org/\u003c/span\u003e\u003cspan address=\"https://obis.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e), Taxonomic Catalog of the Fauna of Brazil (CTFB) (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://fauna.jbrj.gov.br\u003c/span\u003e\u003cspan address=\"http://fauna.jbrj.gov.br\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) and on the speciesLink network (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.splink.org.br/\u003c/span\u003e\u003cspan address=\"http://www.splink.org.br/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) were investigated.\u003c/p\u003e \u003cp\u003eThe search was conducted between November and December 2024, and the terms used to filter the articles were (\u0026ldquo;\u003cem\u003eTenagodus modestus\u003c/em\u003e\u0026rdquo; \u0026ldquo;\u003cem\u003eTenagodus\u003c/em\u003e\u0026rdquo; OR Siliquariidae OR \u0026ldquo;worm-snails\u0026rdquo; OR \u0026ldquo;Slit wormsnail\u0026rdquo;).\u003c/p\u003e \u003cp\u003eFurthermore, records of gastropod mollusks listed and reported by the CEPNOR, which conducts continuous monitoring of marine biodiversity on the Amazon Continental Shelf, were consulted.\u003c/p\u003e"},{"header":"RESULTS AND DISCUSSION","content":"\u003cp\u003eThe three specimens found during the scientific expedition were associated with corals (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA) and rhodoliths (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB), which contradicts what was indicated by Bieler (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), who found the species generally associated with sponges as a substrate for attachment.\u003c/p\u003e \u003cp\u003eThe individuals found are between 60 and 80 mm long, which is consistent with previously recorded animals that generally had a total length of less than 80 mm. Even so, they are considered relatively large individuals and can reach up to 150 mm in length (Bieler, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Rosenberg, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA review of the literature and databases revealed other occurrences of the species in the region. The first record, in GBIF, was in 1975; 3 records from the CEPNOR report the mollusk as bycatch in snapper fishing in 2023; and, more recently, Chagas et al. (2025) described its occurrence in 2020 in the intertidal zone, in a mangrove area located in the estuary of the Primavera River, on the Amazon coast (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis study presents the species in a new area on the northern coast of Brazil, where it is found associated with coral reefs and rhodoliths (calcareous rocks). Based on these records, the presence of the species in the region is confirmed, and an increase in its biogeography along the Brazilian coast is indicated, beyond that estimated by Chagas et al. (2025) in the intertidal zone off the coast of the state of Par\u0026aacute;.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eThus, the biogeographical expansion of \u003cem\u003eTenagodus modestus\u003c/em\u003e in the Northern Region of Brazil, from the state of Amap\u0026aacute; to the coast of the state of0 Esp\u0026iacute;rito Santo. This study contributes to further research on the benthic biodiversity present on the Amazonian continental shelf.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank Centro Nacional de Pesquisa e Conserva\u0026ccedil;\u0026atilde;o da Biodiversidade Marinha do Norte CEPNOR/ICMBio) and crew of the research vessel Soloncy Moura.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJ.A.S.S. and A.C.M. wrote the main text of the manuscript. All authors (S.S.O., A.P.B.C., W.C.R.S., M.R.F.B., R.A.C. and A.G.C.M.K.) reviewed and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors did not receive support from any organization for the submitted work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBieler R (1990) Sessile slit-shells\u0026ndash;a first look at Tenagodus anatomy and biology (Cerithioidea: Siliquariidae). \u003cem\u003eWestern Society of Malacologists Annual Report\u003c/em\u003e, \u003cem\u003e22\u003c/em\u003e, 21\u0026ndash;22\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBieler R (2004) Sanitation with sponge and plunger: western Atlantic slit-wormsnails (Mollusca: Caenogastropoda: Siliquariidae). Zool J Linn Soc 140(3):307\u0026ndash;333\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCaires RA, Carvalho-Filho A, Rotundo MM, Santos WC, R. D, Klautau AG (2021) C. M. \u003cem\u003ePeixes tele\u0026oacute;steos da costa norte do Brasil\u003c/em\u003e. A. P. Marceniuk (Ed.). Museu Paraense Em\u0026iacute;lio Goeldi\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCollette BB, R\u0026uuml;tzler K (1977) Peixes de recife sobre fundos de esponjas na foz do rio Amazonas\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDall WH (1881) Relat\u0026oacute;rios sobre os resultados da dragagem, sob a supervis\u0026atilde;o de Alexander Agassiz, no Golfo do M\u0026eacute;xico e no Mar do Caribe, 1877-79, pelo navio a vapor Blake do Servi\u0026ccedil;o Geol\u0026oacute;gico da Costa dos EUA. 15. Relat\u0026oacute;rio preliminar sobre os moluscos. Bol do Museu de Zoologia Comparada do Harv Coll 9:33\u0026ndash;144\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Klautau M, Cordeiro AGC, das Chagas APB, Dos Santos RA, Marceniuk WCR, da N\u0026oacute;brega AP, Bentes PSV, B (2025) Hotspots de biodiversidade e esp\u0026eacute;cies amea\u0026ccedil;adas sob influ\u0026ecirc;ncia humana na plataforma continental amaz\u0026ocirc;nica. Relat\u0026oacute;rios Cient\u0026iacute;ficos 15(1):26681\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGBIF Secretariat. Tenagodus modestus (Dall, 1881). GBIF Backbone Taxonomy (2025) Checklist dataset. Available at: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.15468/39omei\u003c/span\u003e\u003cspan address=\"10.15468/39omei\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e Accessed at: 2025, November 18\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePansini M, Cattaneo-Vietti R, Sehiaparelli S (1999) Relationship between sponges and a taxon of obligatory inquilines: the siliquariid molluscs. Memoirs of the Queensland Museum, Nature, 44, 427\u0026ndash;438\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRios EDC (2009) Compendium of Brazilian sea shells. Editora Evangraf\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRosenberg G (2009) Malacolog 4.1.1: A Database of Western Atlantic Marine Mollusca. at: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.malacolog.org\u003c/span\u003e\u003cspan address=\"http://www.malacolog.org\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. Acesso em: 18/03/2020 Accessed at: November 18, 2025\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"thalassas-an-international-journal-of-marine-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"thal","sideBox":"Learn more about [Thalassas: An International Journal of Marine Sciences](http://link.springer.com/journal/41208)","snPcode":"41208","submissionUrl":"https://submission.nature.com/new-submission/41208/3","title":"Thalassas: An International Journal of Marine Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Biogeography, Amazon Continental Shelf, Siliquariidae","lastPublishedDoi":"10.21203/rs.3.rs-8919989/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8919989/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study presents new records of the marine gastropod \u003cem\u003eTenagodus modestus\u003c/em\u003e (Dall, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1881\u003c/span\u003e), a representative of the Siliquariidae family, for the northern coast of Brazil, an extensive and highly biologically productive area composed of an Amazonian Reef System. The aim of this study is to present new occurrences of the gastropod \u003cem\u003eT. modestus\u003c/em\u003e on the North Coast of Brazil and to update the species' distribution along the Brazilian coast. The records were reported based on a review of scientific literature, museum databases, and an expedition carried out during the 1st Amazonian Corals Expedition conducted by the Centro Nacional de Pesquisa e Conserva\u0026ccedil;\u0026atilde;o da Biodiversidade Marinha do Norte - CEPNOR/ICMBio, between March 7 and 14, 2025, aboard the research vessel Soloncy Moura. In total, numerous records were made for the region, indicating that the species is present and contributes to the local biodiversity, and not an occasional occurrence. Thus, we confirm the occurrence of the species on the northern coast of Brazil and indicate an increase in its distribution along the Brazilian coast from Amap\u0026aacute; to Esp\u0026iacute;rito Santo.\u003c/p\u003e","manuscriptTitle":"Distribution of Tenagodus modestus (Dall, 1881) (Mollusca, Siliquariidae) along the northern coast of Brazil: New records and biogeographical notes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-09 15:46:37","doi":"10.21203/rs.3.rs-8919989/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-16T17:48:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-16T17:12:53+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-16T14:27:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"135439785057761006499478976057631587591","date":"2026-03-12T11:31:29+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"82828506697128381908183289648643945410","date":"2026-03-07T11:26:49+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-04T18:11:32+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-04T17:57:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-04T09:05:33+00:00","index":"","fulltext":""},{"type":"submitted","content":"Thalassas: An International Journal of Marine Sciences","date":"2026-02-19T17:54:56+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"thalassas-an-international-journal-of-marine-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"thal","sideBox":"Learn more about [Thalassas: An International Journal of Marine Sciences](http://link.springer.com/journal/41208)","snPcode":"41208","submissionUrl":"https://submission.nature.com/new-submission/41208/3","title":"Thalassas: An International Journal of Marine Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9ec05278-de1f-4566-8e8e-8e3244c927cf","owner":[],"postedDate":"March 9th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-03-16T17:55:31+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-09 15:46:37","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8919989","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8919989","identity":"rs-8919989","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}