Abstract:are two economically important freshwater aquaculture species in China. Hybrids created by interspecific crossing among several fish exhibit increased growth rate, improved disease resistance, and improved environmental tolerance. In this study, the embryonic development of reciprocal hybrids of Basilewsky (DQ and QD) and F2 of (♂) F1 (F2) were described and compared to each other and their parents. Embryonic development was divided into 6 main periods based on anatomical featureszygote, cleavage, blastula, gastrula, embryonic body formation, and hatching. S. chuatsi, with a mean diameter of (1.197±0.052) mm, were both significantly bigger than that of the F1 ( males) with 1.723±0.0519) mm. Compared with the early development of other fish, e.g., , and zebrafish, we found that chromatogenesis and pigment distribution in , and the three hybrids shared common characteristics: chromatogenesis began on the yolk sac just after the closure of the blastopore. Punctiform melanin gradually spread all over the surface of the yolk sac. A neurocyte-shaped pigment subsequently centralized on the oil globule, and pigmentation later appeared on eyes and head. The features of embryonic development in the three hybrids were similar to their parents. DQ began to hatch 37 h post-fertilization at 25.5‒27.7 began to hatch 35 h, 34 h, 33 h, 31 h post-fertilization at 25, 26, 27, and 27.5, respectively. The speed of DQ, QD, and F2 embryonic development at 21.6‒28.7. Newly hatched DQ, QD, and F2 larvae were (4.1±0.4) mm3.5±0.2) mm in length, respectively. The similarity in embryonic development of the three hybrids and their parents, and the progeny of males both indicate a very close phylogenetic relationship between , which is consistent with previous studies employing 11 nuclear loci and the cytochrome b gene.
