Determination of annual reproductive cycle in male sterlet, Acipenser ruthenus using histology and ultrasound imaging

Abstract

The aim of this study was to evaluate seasonal testicular development in the cultured sterlet, Acipenser ruthenus. During annual sexual cycle of male sterlet, stages of gonad maturity were examined using histology and ultrasonography approaches. The histology identified males at different stages of maturity among fish sampled monthly. According to the seasonal changes in the testes, reproductive cycle was divided into four stages including resting, pre-spawning, spawning and post-spawning. The histology examination revealed considerable variation in testicular developmental stages. These changes were identified based on persistent spermatogenesis and asynchronous gonad development in testes, showing regulation of annual gonadal cycle is influenced by season. Also, the results obtained using ultrasound suggested that reproductive stages can be identified based on morphology and tissue echogenicity. At each phase of testicular development, gonadosomatic index (GSI) and number of spermatogenic cysts were variable. The present study focused on determination of annual reproductive development in cultured male sterlet which clearly identifies reproductive stage in each season as valuable guide for future researches on reproductive biology of sterlet. This study presents basic knowledge about reproductive biology in sterlet contributing to optimal broodstocks management that allows comparison of reproductive development among sturgeon species.

Influence of Environmental Temperature and Hormonal Stimulation on the In Vitro Sperm Maturation in Sterlet Acipenser ruthenus in Advance of the Spawning Season

“…As documented by Amiri et al [10], at this stage in the bester large amounts of spermatozoa were released from spermatocysts starting from November and were maintained throughout the winter, while no sign of spontaneous spermiation and no sperm release after hand stripping were observed. A similar situation, when seminiferous tubules were full of spermatozoa, was also described for the testes of several sturgeon species [35,[60][61][62][63][64][65][66][67][68]. All these demonstrate that release of spermatozoa from seminiferous tubules in sturgeon can occur starting at the early overwintering period, irrespectively of the location of the species' natural habitat or farming conditions.…”