{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T02:57:13Z","timestamp":1792119433535,"version":"4.4.0"},"reference-count":50,"publisher":"Wiley","issue":"12","license":[{"start":{"date-parts":[[2024,12,11]],"date-time":"2024-12-11T00:00:00Z","timestamp":1733875200000},"content-version":"vor","delay-in-days":10,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Journal of Morphology"],"published-print":{"date-parts":[[2024,12]]},"abstract":"<jats:title>ABSTRACT<\/jats:title><jats:p>In the phylum Nemertea, the class Hoplonemertea (former Enopla) comprises the largest number of studied species with complex spermatozoa. <jats:italic>Asteronemertes gibsoni<\/jats:italic> Chernyshev, 1991, a nemertean species having a symbiotic relationship with sea stars, is characterized by complex filiform spermatozoa. Here, spermatogenesis and spermatozoon structure in <jats:italic>A. gibsoni<\/jats:italic> have been examined using light and electron microscopy. Numerous proacrosomal vesicles of two kinds have been found in early spermatogenic cells. In spermatozoa, the elongated acrosomal complex consists of two components: a core, which is a spindle\u2010shaped electron\u2010dense acrosomal vesicle with a long anterior end, and its casing of moderate electron density that covers the acrosomal vesicle completely. The acrosomal complex is located laterally relative to the elongated nucleus. The acrosomal casing bears two rows of small, short channels between the nucleus and the electron\u2010dense acrosomal core. In late spermatids, the elongations of the acrosomal complex and the nucleus occur simultaneously and are mediated by numerous microtubules that disappear during the latest stages of spermiogenesis. The flagellum in spermatogenic cells and spermatozoa contains an axoneme with the usual 9\u2009\u00d7\u20092\u2009+\u20092 microtubular organization and is posteriorly oriented in spermatozoa. As known to date, <jats:italic>A. gibsoni<\/jats:italic> has the most modified spermatozoa among investigated Nemertea, and the complex structure of its sperm is suggested to be associated with the reproductive biology, in particular, with fertilization. Additionally, a number of similar ultrastructural features in spermatozoon organization have been found in <jats:italic>A. gibsoni<\/jats:italic> and <jats:italic>Kurilonemertes phyllospadicola<\/jats:italic> whose phylogenetic relationship was previously proven.<\/jats:p>","DOI":"10.1002\/jmor.70014","type":"journal-article","created":{"date-parts":[[2024,12,11]],"date-time":"2024-12-11T19:02:17Z","timestamp":1733943737000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Spermatozoa and Spermatogenesis in the Ribbon Worm <i>Asteronemertes gibsoni<\/i> (Hoplonemertea, Oerstediidae), a Symbiont of Sea Stars"],"prefix":"10.1002","volume":"285","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6499-0195","authenticated-orcid":false,"given":"Olga V.","family":"Yurchenko","sequence":"first","affiliation":[{"name":"A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences Vladivostok Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alexey V.","family":"Chernyshev","sequence":"additional","affiliation":[{"name":"A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences Vladivostok Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2024,12,11]]},"reference":[{"key":"e_1_2_9_2_1","first-page":"181","article-title":"Spermatozoon of Nemertine Malacobdella grossa","volume":"3","author":"Afzelius B.","year":"1971","journal-title":"Journal of Submicroscopic Cytology"},{"key":"e_1_2_9_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/B978-0-08-018006-9.50006-0"},{"key":"e_1_2_9_4_1","doi-asserted-by":"publisher","DOI":"10.1007\/s00435-024-00659-2"},{"key":"e_1_2_9_5_1","first-page":"34","article-title":"Tetrastemma commensalis and Asteronemertes gibsoni Gen. et sp. n. (Hoplonemertini, Tetrastemmidae)\u2014Commensals of the Starfishes","volume":"70","author":"Chernyshev A. 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