Study of Embryonic and Postembryonic Development of the Hybrid(Ctenopharyngodon idellus ♀ ×Elopichthys bambusa♂)

[ Objective ] The purpose was to provide a reference for crossbreeding of grass carp. [ Method] We conducted hybridization between Ctenopharyngodon ideUus （ ♀ ） and Elopichthys bambusa ♂ ） by artificial methods. The process of embryo and postembryonic development were observed and recorded. [ Result ] The fertilization rate, hatching rate and survival rate of the hybrid F1 were （75.8 ± 6. 2）%, （41.9 ± 8.2）% and （9.3± 3.7）%, respectively. At the water temperature of 20.1 -21.6℃, the larvae was hatched for about 34 h and 25 rain after fertilization. The whole length of newly-hatched larvae of the hybrid Fl was （5.8 ± 0.12） mm. The larvae could feed rotifer and unicellular algae after 3 or 4 days hatching. Postembryonic development of the hybrid at the formation of scales, lasted for 65 days when the young was（74.0 ± 2.1 ） mm in whole length. [ Conclusion] The embryonic development of hybrid F1 was intermediate to their parents, the form of the hybrid F1 was similar to that of their female line of grass carp. The growth rate of larva was faster than that of grass carp and similar to that of their paternal fish.

Embryonic and Postembryonic Development of Percocypris pingi pingi( Tchang)

This study aimed to investigate the morphological characteristics of Percocypris pingi pingi （Tchang） at the embryonic and postembryonic developmental periods and to demonstrate the early developmental stage of P. pingi pingi （Tchang）. According to the results, the fully mature eggs were spherical, orange-col- ored, sticky, 2.2 mm in diameter; the maximum outer diameter reached 3.2 -3.8 mm after absorbing water. When water temperature was （18 -＋ 0.5） ~C, the first cleavage occun~ at 2h 28 min post-fertilization; organs began to form at 45 h 23 min post-fertilization; larvae were hatched at 126 h 28 min post-fertilization. Newly hatched larvae exhibited a total length of 10.4 mm, with large and compressed yolk sacs. According to the morphological characteristics, the embryonic de- velopmental process of P. pingi pingi （Tchang） could be divided into seven continuous stages, including fertilized egg stage, cleavage stage, blastula stage, early gastrula stage, neurala stage, organ formation stage and hatching stage, which were further divided into 32 phases. When water temperature ranged from 18.8 ~C to 25.0 ~C, the whole developmental process of P. pingi pingi （Tchang） from larvae to juveniles lasted 93 d. According to the morphological and ecological charac- teristics, the pestembryonic developmental process of P. pingi pingi （Tchang） could be divided into three stages, including yolk-sac larva stage, late larva stage and junenile stage. This study laid solid foundation for .

Differences in postembryonic dorsal fin development resulted in phenotypic divergence in two goldfish strains, Red Cap Oranda and Ranchu

Goldfish(Carassius auratus auratus)are important ornamental fish that have experienced extreme anthropogenic selection and exhibit diverse phenotypes.Loss of the dorsal fin is a key characteristic that distinguishes the Egg-goldfish from the Wen-goldfish.However,the mechanisms underlying the divergence in dorsal fin development are still unknown between the Egg-goldfish and the Wen-goldfish.In this study,we sought to unravel the postembryonic developmental processes of two goldfish strains,Red Cap Oranda,a representative of the Wen-goldfish,and Ranchu,a representative of the Egg-goldfish.We examined the developmental morphology of the dorsal fin in five-month-old goldfish larvae using both Alcian blue-alizarin red staining and X-ray photography.We showed that the developmental processes of the dorsal fin fold were different in Ranchu compared to Red Cap Oranda,despite similarity in their general developmental processes.We categorized the postembryonic development of Ranchu larvae into four types based on the number of the initial residual dorsal fin fold appearing at protruding-mouth stage.The number,size and position of the initial residual dorsal fin fold appeared at hatching affected and eventually determined the phenotypic variations in dorsal fin defects in Ranchu.In addition,we genotyped the eomesa gene to determine whether it would be a candidate gene responsible for the loss of the dorsal fin in Ranchu.The eomesa CDS sequence exhibited no nonsense mutation in Ranchu.In summary,the absence of the dorsal fin fold during postembryonic development eventually resulted in the loss of the dorsal fin in Ranchu.Further investigation is required to determine whether other genes and developmental pathways play important roles in the loss of the dorsal fin in Ranchu.