Embryonic Development and Morphologic Observations of Newly-Hatched Cheilinus undulatus Larvae

Abstract:

The humphead wrasse, Cheilinus undulatus, is one of the most famous endangered reef fish in the world. As a social hermaphroditic fish, it has special biological characteristics and high economic value. In this study, we observed the embryonic development of C. undulatus and analyzed its features under a microscopy. Six periods, including zygote, cleavage, blastula, gastrula-neural, organogenesis, and hatching, were divided during the embryonic development of C. undulatus. These 6 periods include 26 stages, including zygote, blastoderm formation, multi-cell, morula, and tail bud stage etc. The results showed that C. undulatus had a float, transparent, spherical egg with a big oil globule. The diameter (635.6±50.0) μm of the egg was obviously shorter than eggs of many marine fishes. The neural plate appeared in the mid to late gastrula stage, and the embryonic development of C. undulatus was remarkably quicker than other fishes under the same condition. The fertilized eggs were hatched after 15.5 h at water temperature of 27.7−29.0℃ and salinity of 30. The total length of newly-hatched larvae were (1305.5±50.0) μm with an elliptic large yolk sac over the head and a shining oil globule in the front of it. These results suggest that the embryo development of C. undulatus was faster than many other fishes due to smaller egg. The special embryonic development features of the humphead wrasse may cause high mortality in the post embryonic stage.