engleski

Histological analysis of the silver smelt, Argentina sphyraena (Pisces, Argentinidae) gonads during the spawning period

The silver smelt, Argentina sphyraena is a bathydemersal species inhabiting the continental shelf and upper slope waters of the eastern North Atlantic and the Mediterranean. This species is usually found at depths between 100 and 200 m in the Adriatic where its spawning period is extended from winter to spring. Enhanced by the lack of data on the silver smelt reproductive biology, female and male gonads were processed for routine histology in order to describe developmental stages of germ cells during the spawning period of investigated species in the eastern Adriatic. Analysis revealed asynchronous development of the ovaries and testes with germ cells of both sex being in different stages of development. Four stages in oocyte development were observed. Primary growth stage included oocytes in perinucleolus phase, while chromatin nucleolar oocytes were not observed. Average cellular diameter of perinucleolar oocytes was 96.73 µm (± 15.07 SD) and oocytes in cortical alveolus stage 215.22 µm (± 45.02 SD). Vitellogenic growth stage included early and late vitellogenic oocytes, with their diameters of 365.53 µm (± 39.37 SD) and 519.15 µm (± 30.04 SD), respectively. Maturation stage was characterized by advanced yolked oocytes with an average diameter of 705.50 µm (± 67.43 SD). Testes were staged as mid-spermatogenic, since approximately equal numbers of spermatocytes, spermatids and spermatozoa were observed. The diameter of seminiferous tubules varied from 143.32 to 239.66 µm, with an average value of 188.34 µm (± 22.50 SD). Presented data indicate that A. sphyraena is an asynchronous spawner that has prolonged spawning season.

Argentina sphyraena; reproduction; Adriatic

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