Do eutardigrades have a copulatory organ? The case of Halobiotus crispae Kristensen

Biserova, N.M.; Bannikova, M.A.; Nikolaeva, O.V.; Aleoshin, V.V.

Авторы: Biserova N.M., Bannikova M.A., Nikolaeva O.V., Aleoshin V.V.
Журнал: Зоология беспозвоночных
Том: 22
Номер: 1
Год издания: 2025
Издательство: Товарищество науч. изд. КМК
Местоположение издательства: М.
Первая страница: 8
Последняя страница: 20
DOI: 10.15298/invertzool.22.1.01
Аннотация: ABSTRACT: Reproductive strategies of tardigrades vary considerably among taxa. Speciesof Heterotardigrada have separate gonopore and anus, whereas Eutardigrada species havea single cloacal opening, which is a shared exit from the cloaca, hindgut, and Malpighiantubules. While internal fertilization has been hypothesized for certain species based on thepresence of spermatozoa in female spermathecae, the mechanism of sperm transfer remainsundocumented. Notably, sexual dimorphism has not previously been reported in eutardigrades.In this study, males and females of the eutardigrade Halobiotus crispae Kristensen, 1982were collected from sand samples in the intertidal zone of Olenevsky Island, White Sea,and analyzed using molecular, electron-microscopy and immunocytochemical methods. Ourfindings advance the understanding of H. crispae reproductive biology, including the firstdocumented evidence of sexual dimorphism in eutardigrades. Males possess a protrusiblecloacal cylinder, hypothesized to function as a copulatory organ. Distinct morphologicaldifferences in cloacal structure were observed in two sexes. Males have oval-shaped andsmaller cloaca with smaller cloacal plates; females have larger, diamond-shaped cloaca,with acute-triangular cloacal plates. Additionally, sensory organs and musculature near thecloacal plates and in the fourth pair of legs have been found which suggest neural regulationduring mating, potentially guiding copulatory interactions. The proposed role of the malecloacal cylinder as a copulatory organ supports the hypothesis of internal fertilization in thisgroup, changing the current understanding of reproductive strategies in tardigrades. Thesefindings underscore the need for deeper exploration of tardigrade reproduction, particularlyto clarify the prevalence and mechanisms of internal fertilization across species.
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Do eutardigrades have a copulatory organ? The case of Halobiotus crispae Kristensenстатья Исследовательская статья

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