ontogeny of gill structure in sterlet, acipenser ruthenus (linnaeus, 1758)

the ontogeny of the gill structure in starlet ( acipenser ruthenus ) was studied histologically from hatching up to 50 days post hatching (dph). based on the obtained results, the first developmental phase of the biological systems in this species was started from hatching with an intense organogenesis and the second phase from 9 dph with the beginning of exogenous feeding. the gill anlage was visible in the pharyngeal region at 1 dph. the mouth and gill slits opened at 2 dph along with the formation of four pairs of the primordial gill arches. at 3 dph, the primordial gill filaments formed. the development of the primordial lamellae and pseudobranch were observed at 8 dph. the primordial gill filaments of the pseudobranch were appeared at 9 dph. the chloride cells appeared at 8 dph on the base of the gill filaments. the gill structure of the sterlet larvae at 31 dph was similar to that of the adults. the results of this study provided a proper indicator for aquaculture practice of starlet.