Observation on embryonic development, morphology and growth of larvae and juveniles of Aspiorhynchus laticeps

In this study, the embryonic development and morphological changes of larvae and juveniles of Aspiorhynchus laticeps were observed by dry fertilization. The results show that the eggs were sinking eggs, and the color of egg cells was bluish gray and slightly sticky. A total of 21.45×10⁴ mature eggs were obtained and the average of fertilization rate and hatching rate were 88.95% and 93.27%, respectively. The diameter of mature eggs was (2.46±0.13) mm, and that of fertilized eggs was (3.42±0.15) mm. According to the external morphology and typical characteristics of embryo development, it can be divided into eight stages: fertilization, cleavage, blastocyst, gastrula, neuroembryo, organ differentiation and hatching. It took 115.5 h for the whole embryo to develop, and the total accumulative temperature was 3 765.42 ℃·h. The total length of newly hatched larvae was (7.58±0.31) mm. The development of prelarva from hatching to yolk absorption took approximately 9 d, and the specific growth rate (SGR) of total length was (3.63±0.68)% and that of total length was (3.51±2.10)%. The juvenile period lasted 63 d and the SGR of total length was (1.32±0.17)%, significantly different from those of early and late larval stages (P<0.05). The total length and body mass of A. laticeps young fish was (15.71±0.89) cm and (28.29±6.15) g, respectively, and the body color and body shape were similar to adult fish.