Embryonic and larval development of Oxygymnocypris stewartii in the Yarlung Zangbo River
雅鲁藏布江尖裸鲤胚胎和仔稚鱼发育的研究

This study was performed to describe for the first time the embryogenesis and the yolk-sac larval development of Oxygymnocypris stewartii that inhabits the cold food-impoverished habitats in the Yarlung Zangbo River, Tibetan Plateau. The unfertilized mature eggs of O. stewartii, were spherical, yellowish, demersal and 2.57 ± 0.07 mm in diameter. After fertilization and hydration, the fully swollen eggs were translucent, 3.22 ± 0.07 mm in diameter. After 265 h, O. stewartii larvae were hatched with a total length of 10.27 ± 0.15 mm at the water temperature of 9.5 ~ 11.8 oC. Around 20 day after hatching, the yolk sac of larva was absorbed completely with a total length of 15.22 ± 0.27 mm, and 80 day after hatching, hip scales appeared with a total length of 23.65 ± 0.59 mm. In comparison with other Schizothoracinae, the traits of early development of O. stewartii may enable the embryos to adapt to the torrential environment with low food rations in Tibetan plateau.