Ultrastructure of gametogenesis in the ovotestis of an estuarine pulmonate slug, Onchidium tigrinum (Stoliczka, 1869)
2018
Roy, Soumen | Chaki, Korak Kanti | Nag, Tapas Chandra | Misra, Kamales Kumar
The pulmonate slug Onchidium tigrinum (Stoliczka, 1869) is an estuarine protandrous gastropod. Transmission electron microscopy of both the gonadal and somatic cell populations of the ovotestis of the slug is documented. The acini of smaller slugs are comprised of developing spermatogenic cells and three to four small ill-developed oocytes. Details of the microscopic structures of Sertoli cells, interacinar cells and acinar boundary are described in-depth, revealing their secretory function. Sertoli cells are more numerous in the ovotestes of smaller slugs than in those of larger slugs. Tunnelling nanotubes of 200–400 nm in diameter are described for the first time in the Sertoli cells of molluscan ovotestis. These nanotubes may help to supply various cellular materials into distantly developing spermatogenic cells. The acini of larger slugs possess 2–3 mature oocytes along with a few spermatogenic cells. Sertoli cells, interacinar cells and spermatogonial cells are fewer in number in the acini of the ovotestis of larger individuals establishing the predominance of oogenesis in this phase of life. The number of oocytes per acinus is analysed in relation to the habitat of the pulmonates.
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