Postembryonic Ontogeny of Lake Sturgeon Acipenser Fulvescens with Quantitative Data of Forebrain Growth - Abstract
External morphological changes along lake sturgeon postembryonic development from hatching to year-0 juvenile were described. We also provided data for the growth of the olfactory bulb and telencephalon during the period based on micrographs of confocal imaging. By the time of hatching, yolk-sac larvae were approximately 1 cm in total length with many features corresponding to the pharyngula period of zebrafish embryos. Larval Stage started with the beginning of exogenous feeding when fish snout was flattened and specialized into triangular-shaped rostrum. By then, the larvae were approximately 2 cm in in total length and the forebrain was differentiated into the telencephalon and diencephalon. Sturgeon larvae transformed their eel-like body into spindle-shaped trunk armored with five rows of scutes at late Larval Stage. Juvenile Stage, when fish were over 4 cm in total length, began with the complete transformation of the ray-fin tail and disappearance of fin folds. At 7-8 cm in total length, pigment distributions resembled those in adults. In early Juvenile Stage, the olfactory bulb reduced it’s widthwise expansion pace while maintained longitudinal growth. Anatomical features of the olfactory bulb stabilized in fish larger than 5.5 cm. Quantitative data indicated steady longitudinal growth of the telencephalon during the period examined while an increase in width slowed down after fish reached 5.5-6.5 cm. The data suggest that the forebrain development is most active in fish smaller than 5.5 cm. This time period included two vulnerable phases in which fish
transformed themselves into new developmental stages. Our study has provided valuable information for future research and fisheries of lake sturgeon.