A preliminary study on development of Discogobio yunnanensis larvae and juveniles

In order to investigate the basic biological data of Discogobio yunnanensis larvae and juveniles and provide theoretical guidance for large-scale artificial breeding, we carried out an experiment at water temperature of (20±0.5) ℃ and observed the development of D.yunnanensis larvae and juveniles under digital camera system, described the external morphology and internal structure characteristics qualitatively or quantitatively. We found that the newly hatched larvae had the body mass of (0.012±0.001) g and the total length of (7.16±0.03) mm. The length and height of yolk sac were (4.04±0.02) mm and (1.35±0.02) mm, respectively. The larvae started feeding on 9^th day and the yolk sac was absorbed thoroughly on 28^th day after hatching. The stage of mixed nutrition lasted 19 d. It is speculated that the existence of this stage was conducive to establishing nutritional relationship between larvae and the outside world, and reducing the mortality rate at early developmental stage of fish. The scales appeared and developed entirely on 45^th and 80^th day after hatching. The late stage of larva lasted 17 d. In addition, we made a little adjustment to the juvenile stage according to the characteristics of D.yunnanensis, taking 165^th day after hatching as the sign of the end of juvenile stage when the sucking disc developed well. The juvenile stage lasted 120 d.