Observations on morphology of post-embryonic development and histology of sensory organs in larval and juvenile Siberian sturgeon, Acipenser baerii

Abstract

Siberian sturgeon,Acipenser baerii,one of the oldest extant cold-water fish species in the world,are of considerable research and economic value.We documented the postembryonic development of the Siberian stur-geon by monitoring morphological characteristics and cell types in retina,taste buds,olfactory sac,and ampullary organs in the larvae.The stages of postembryonic development were defined based on both the external morphol-ogy and the internal organ characteristics.Larvae were reared at a water temperature of(18.0±1.0)℃ and a pH of 7.0?7.5.The newly hatched larvae(day 0) were(9.05±0.14) mm long.During the early-stages of development(days 0–7),the larvae were nurtured by a large yolk sac and the eye was the primary sense organ.The late-stage larvae(day 8?–22) were characterized by the disappearance of the yolk sac and initiation of active feeding,the formation of fins and fin rays,a shift in habitat use towards the bottom of the water column,and the completion of organ differentiation.As larvae reached the juvenile stage(day 23–57),the scutes begin to form,the organs tended to become fully developed,and the external morphology and body color pattern gradually matured into the adult pattern.We observed some differences in the development characteristics of the primary sensory organs in Sibe-rian sturgeon relative to other teleosts.Our observations suggest that Siberian sturgeon is an ancient species that occupy a unique position during the evolution of teleosts.