| This experiment is base on the research of the embryonic and postembryonic development of the hybrid F1of Ancherythroculter nigrocauda (♂) and Culter alburnus (♀). According to the ontogeny of larval digestive system and feeding habits, we get the results as follows:1. The hybridizations between parent fish of Ancherythroculter nigrocauda (♂) and Culter alburnus (♀) were carried out in July,2010, the embryonic and postembryonic development of the hybrid were observed and recorded. Result shows that:the fertilized eggs had a light yellow surface, a sphere-like form and a diameter of0.86-0.95mm.The progress of embryonic developmental is composed of7stages:One cell stage, Cleavage stage, Blastula stage, Neumla stage, Gastrula stage, apparatus-forming stage, Hatching-out stage and can be divided further into29periods. At water temperature of24-25℃, the first cleavage was at40min after fertilization(af); the most larvae hatched out at26h af when the total length of the newly hatched larvae ranged from4.5to5.05mm and the accumulative temperature reached647.7℃· h. Postembryonic development of hybrid is consisted of larvae phase and juvenile phase. The larvae phase developed completely at288h after hatching (ah) and juvenile phase sustained240h during which scales emerged and covered the fish surface. A one-chambered gas bladder was observed at104h ah, meanwhile larvae began to feed exogenously, and two chambers occurred at264h ah. The metamorphosis occurred during264to288h ah. The embryonic stage is the onset of the whole life history of fish. During this stage, the larvae are susceptible to circumstance. In a word ascertaining on embryonic development not only accumulates the fundamental data of Culture fish but also provides theoretical guide for artificial rearing.2. The histological development of larval digestive system was studied by the adoption of HE staining. The ontogeny of intestine, esophagus and buccopharyngeal cavity in1-30d ah larvae were observed. The results showed that:intestine, esophagus and buccopharyngeal cavity appeared at3d ah. At5d ah, testes buds and oral valve appeared in buccopharyngeal cavity, meanwhile, striated border and mucous membrane were also observed in intestine. The buccopharyngeal cavity developed completely at9d ah. At12d ah, the straight intestine differentiated into a "Z"-formed tube with anterior intestine, middle intestine and hind intestine. In general, although the larvae of5d ah began feeding exogenously, its digestive system didn’t develop completely in function. Buccopharyngeal cavity and esophagus were not completed until9d ah, and the intestine completed in histology at30d ah. The structure of larval digestive gut in early history has a close relationship with digestive function. Thereby the study on digestive gut could help to ascertain its physiological and functional development. In this way, the theoretical reference could be provided for the larval rearing process.3. The hybrid F1fry grew rapidly after hatching. The length of larvae during period of5to30d ah increased from6.68±0.87mm to27.61±5.51mm. Relationship equation between body length and body weight was described as W=0.0061L3.2452(W:body weight; L:body length). The major preys are rotifers and Pandorian morum which accounted for20-30%of mouth diameter in5d ah larval. Fish mainly consumed cladocerans during6to16d ah. On18d ah, fish shifted diets to chironomids larvae and adults. In addition, the feeding rhythm of fry in early life belongs to diurnal rhythm. Fish of8d ah and30d ah feed on preys within8:00-17:00mainly. One feeding peak of8d ah fish was14:00-17:00, while two feeding peaks of30d ah fish were5:00-8:00and14:00-17:00. Feeding state of larvae fish is an important factor which determines its own growth. In conclusion investigations into fish growth and feeding habit provide significant evidence in establishing rearing strategy to ensure a high survival ratio. |
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