Study On Development Of The Digestive System In Yellow Catfish Pelteobagrus Fulvidraco Larvae

Yellow catfish(Pelteobagrus fulvidraco) is an important commercial freshwater species in China. Because of its high meat quality, the yellow catfish is most welcome among people. The scale of P. fulvidraco rearing becomes larger in recent years. However, the larvae have a very high death rate during the cultivating, which is seriously restricted the large-scale culture of P. fulvidraco. In order to enhance the success of larvae rearing of P. fulvidraco, we need to know the ontogeny of its digestive system thoroughly. The purpose of this study was to understand the morphological structure of digestive tract and its function development during the ontogeny of P. fulvidraco. AB-PAS stain and real-time PCR methods were adopted in the study. We hope that this information would provide fundamental knowledge for larvae rearing management for this species. The main results are shown as follows.1. By adopting HE staining and AB-PAS staining, the study focuses on histology of peptic in P. fulvidraco larvae. At 1 dph (Day post-hatching), the buccopharyngeal cavity, stomach and intestine of larvae was close and the epithelial cells of the stomach and intestine were undifferentiated. AB-PAS staining was negative. At 3 dph, the larvae opening, the taste bud could find in Buccopharyngeal cavity, the epithelial cells of esophagus differentiated into goblet cells, the epithelial cells of the stomach which were simple columnar epithelium differentiated into gastric glands, gastric pits and goblet cells. AB-PAS staining was negative. At 5 dph, AB-PAS staining showed the mucous cells of typeⅡwere in epithelial of buccopharyngeal cavity and esophagus. This is helpful for food swallowing. The mucous cells of typeⅠwere found in epithelial of the stomach. This has an adjusting efforts to the acidic condition in stomach. The mucous cells of typeⅢand mucous cells of typeⅣwere in epithelial of intestine. At 15 dph, AB-PAS staining showed the mucous cells of typeⅢwere found in esophagus. At 25 dph, a great many gastric glands were in cardia stomach and none gastric gland found in pylorus stomach. Muscular layer differentiated into three layer, internal layer was angle muscular, mindset layer was circular muscular and external layer was portrait muscular. The results show that the histology of digestive tract of P. fulvidraco larvae grew fast at 3 dph, the organizational structure became integrity gradually with age.2. By adopting real-time PCR, the study focuses on detection and quantitation of pepsinogen, H+/K+-ATPase and trypsinogen genes expression of P. fulvidraco larvae. The results show that pepsinogen, H+/K+-ATPase and trypsinogen genes expression at 1 dph and the quantitation were very rare. The pepsinogen gene expression increased significantly from 1 to 8 dph, increased fluctuantly from 8 to 23 dph and rose sharply from 23 to 30 dph. The trend of trypsinogen gene expression was similar to pepsinogen gene expression and the quantitaiton increased significantly from 1 to 6 dph, increased fluctuantly from 6 to 23 dph and rose sharply from 23 to 30 dph. The quality of H+/K+-ATPase gene expression grew linearly from 1 to 30 dph. This means that the condition of stomach in P. fulvidraco larvae gradually changed acid post hatching. Mean while, digestive function grows rapid and digestive function was imperfect at 6 to 23 dph.3. Based on the results of the present study, we conclude that P. fulvidraco larvae were still in a sensitive period and digestive function was imperfect from 6 to 23 dph. The weaning time for P. fulvidraco larvae would be better after 23 dph.