The Post Embryonic Development Of The Chinese Giant Salamander Gastrointestinal 5-ht Cells

Chinese giant salamander(Andrias davidianus) called giant salamander, under the Amphibia. Caudata, Implicit gills salamander families. Disturbed only in China, giant salamander is the world's largest extant amphibians and the longest life ancient animal.Morphological changes of gastrointestinal tract during postembryonic development of the Chinese giant salamander Andrias davidianus were observed. And immunohistochemistry location of the 5-HT cells in the gastrointestinal tract of giant salamander during postembryonic development was studied. It aims to study the essential characteristics of formation, differentiation and development, and accumulate the basic data such as the development, artificial breeding of giant salamander and embryonic development of the digestive system in other vertebrate. The main results and conclusions as follows:1. Anatomical observations showed that gastrointestinal tract was short without differentiation between the stomach and the intestine on the 7th day after hatching (DAH). The differentiation between the stomach and the intestine was observed on the 21st DAH. On the 35th DAH, the stomach, small intestine and large intestine were observed, stomach was intumescent. the length of the intestine increased. At this point, gastrointestinal tract organs were complete morphological differentiation. On the 56th to 350th DAH. the segments of gastrointestinal tract gradually became larger, the length gradually increased.2. Histology observations showed that the structure of gastrointestinal tract was simple only with mucous epithelium on the 7th DAH. On the 21st DAH. the stomach was composed by mucous epithelium, lamina propria. muscularis and adventitia; intestine consisted of mucous epithelium and muscularis. On the 35th DAH. muscularis mucosa can be observed in the stomach; large intestine consisted of mucous epithelium and muscularis. Adventitia of small intestine was formed on the 77th DAH. On the 98th DAH. submucosa of the stomach, a clear lamina propria of small intestine and adventitia of large intestinal could be observed. Lamina propria of large intestine was formed on the 119th DAH. On the 180th DAH, the gastrointestinal tract wall had mucous epithelium.lamina propria. submucosa. muscularis and adventitia. As the postembryonic development progressed.the structure of the gastrointestinal tract improved gradually.3. Immunohistochemical observations showed that 5-HT positive cells were detected in the stomach and small intestine, but not found in the large intestine on the 98th DAH.5-HT positive cells were observed on the 119th DAH. The distribution density of 5-HT positive cells in different organs at the same stage was that it was the most in the small intestine, followed by the stomach, and it was the least in the large intestine at the same development stage.4. Immunohistochemical observations showed that in the stomach, the growth was not obvious from 98th DAH to 147th DAH. There was significant increase between 180th DAH and 147th DAH. There was extremely significant difference between 350th DAH and 180th DAH. In the small intestine. the density of 5-HT cells increased from 98th DAH to 350th DAH. but the growth was not obvious. In the large intestine, there was no significant increase between 147th DAH and 119th. After 147th DAH, there was extremely significant difference between 350th DAH and 180th DAH that was the same as 180th DAH and 147th DAH. The distribution of 5-HT positive cells in the same organ at the different stages is:the density of 5-HT cells of gastrointestinal tract in giant salamander was increased gradually during postembryonic development.