Early Development Of Four Schizothoraeinae Fishes In The Yarlung Zangbo River, Tibet

All the four Schizothoraeinae fishes (Oxygymnocypris stewartii, Schizopygopsis younghusbandi, Schizothorax waltoni, Schizothorax o'connori), only distributed in the Yarlung Zangbo River and its tributaries, are endemic fishes of Tibet and have an importantly economic value. Recently, due to their limited natural distribution and over-exploitation for its remarkable economic-important value, they have declined dramatically. Therefore, the study on their early development from the perspective of ecology and adaptation to its environment could contribute to better understanding of the species and the efficient conservation. The key points of the present study are as follows:1. 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℃. 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.2. The unfertilized mature eggs of S. younghusbandi, were spherical, golden yellowish, demersal and 2.50±0.08 mm in diameter. After fertilization and hydration, the fully swollen eggs were translucent,3.54±0.07 mm in diameter. After 295 h, S. younghusbandi larvae were hatched with a total length of 10.86±0.33 mm at the water temperature of 9.5～11.1℃. Around 18 day after hatching, the yolk sac of larva was absorbed completely with a total length of 15.58±0.44 mm, and 77 day after hatching, hip scales appeared with a total length of 23.65±0.59 mm, lateral line completely appeared, the body type and color are Similar to adult fish.3. The unfertilized mature eggs of S. waltoni, were spherical, brown, demersal and 2.95±0.09 mm in diameter. After fertilization and hydration, the fully swollen eggs were translucent,4.03±0.06 mm in diameter. After 264 h, S. waltoni larvae were hatched with a total length of 10.67±0.17 mm at the water temperature of 10.0～12.0℃. Around 23 day after hatching, the yolk sac of larva was absorbed completely with a total length of 15.27±0.26 mm.69 day after hatching, lateral line completely appeared with a total length of 20.92±0.44 mm, the body type and color are Similar to adult fish.4. The unfertilized mature eggs of S. o'connori, were spherical, yellowish, demersal and 2.40±0.12 mm in diameter. After fertilization and hydration, the fully swollen eggs were translucent,3.67±0.10 mm in diameter. After 190 h, S. o'connori larvae were hatched with a total length of 9.84±0.28 mm at the water temperature of 12.1～13.8℃. Around 22 day after hatching, the yolk sac of larva was absorbed completely with a total length of 14.15±0.23 mm.65 day after hatching, lateral line completely appeared with a total length of 27.65±0.45 mm, the body type and color are Similar to adult fish.These early life-history traits reflect the coevolution of the four Schizothoraeinae fishes with its habitat.