Histological Observation Of The Chinese Giant Salamander Gastrointestinal Embryo Development

During the whole vital movement, the organism depend on the digestive system to absorb nutrient substances to satisfy the requirement of metabolism. So the development and perfection of digestive system is the structure foundation of nutrition intake and growth. The gastrointestinal tract is the biggest and most complicated organ with a lot of endocrine cells. The 5-HT which is excreted by the 5-HTIR cells in the digestive system was the important NT and modifier. It plays an important role in the externalization of the gastrointestinal mucus, muscle contraction and hemangiectasia, the regulation effect on the digestive system of 5-HT is very important.Chinese giant salamander is tailed amphibian that disturbed only in China. Chinese giant salamander is the biggest and the longest life amphibian in actual existence. So it is referred as live fossil. In this text, the Chinese giant salamander was the research object. The histological structure of the gastrointestinal tract at different stages during the postembryonic development was observed. The mean optical density of 5-HTIR of the gastrointestinal tract cells in the same organ of different stages and in different organs at same stage were studied. We summarized the changes of histological structure during the postembryonic development. The law of development of 5-HTIR in different organs of the gastrointestinal tract in the Anamniota and the law of development of 5-HTIR of the gastrointestinal tract in the amphibian were approached. We hope that these researches were benefit to the developmental biology, artificial breeding and resource conservation about the Chinese giant salamander. The research results as follows:1. The stomach and intestines differentiated in gastrointestinal tract of the larva after hatching for 77 days. But the differentiation is not obvious. The small intestines and large intestines can not be discriminated. The stomach was becoming larger and the intestines bent obviously. And the segment of the intestines which is close to cloaca became larger and longer between 122days and 242days after hatching. Now, the stomach, small intestines and large intestines could be clearly identified. Small intestines and large intestines of the subadult giant salamander also could be clearly identified. In this period, the duodenum and small intestines can be identified. During the postembryonic development, the gastrointestinal tract of the Chinese giant salamander gradually became perfect.2. The gastrointestinal tract wasn't well-developed in the larva after hatching for 77 days. There were only two layers—mucosa and adventitia, the intestinal villus were columnar. The three layers (mucosa, muscular layer and adventitia) in the stomach of larva after hatching for 122 days developed well and simple coiled tubular glands in the lamina propria occured. The intestinal villus was very rich and was digitiform. There were striated border on the intestinal villus and there were less globlet cells among the cellula columnoepithelialis. The three layers (mucosa, muscular layer and adventitia) were clearly identified in stomach, small intestine and large intestine in the larva after hatching for 242 days. The gastric glands in the gastric pits were abundant. However, there were no intestinal glands. The structure of the gastrointestinal tract in subadult became perfect. And the four layers (mucosa, submucosa, muscular layer and adventitia) were identified clearly. The gastric pits could be found and gastric glands were much abundant. There were abundant simple coiled tubular glands in the lamina propria. And the intestinal villus that was lobiform was very rich in duodenum. Among the cellula columnoepithelialis, the globlet cells were very abundant. While, the posterior segment of the intestinal villus was digitiform. And there were less globlet cells. Among the enterocyte in large intestine, there were globlet cells. During the postembryonic development, the structure of the gastrointestinal tract gradually became perfect.3. The examine result of 5-HTIR cells in gastrointestinal tract of the Chinese giant salamander was detected. The distribution differences in the same organs at different development stages were as follows: In stomach, there was no significant difference between the larva after hatching for 77 days and the larva after hatching for 122 days. Also there was no significant difference between the larva after hatching for 77 days and the larva after hatching for 242 days. But there were significant differences between the larva after hatching for 77 days and subadult. There was no significant difference between the larva after hatching for 122 days and the others after hatching in different stages. There was no significant difference between the larva after hatching for 242 days and subadult. In small intestine, there was no significant difference between the larva after hatching for 77 days and the larva after hatching for 122 days. There was significant difference between the larva after hatching for 77 days and the larva after hatching for 242 days. And the differences were extremely significant between the larva after hatching for 77 days and subadult. There was no significant difference between the larva after hatching for 122 days and the larva after hatching for 242 days. And there were significant differences between the larva after hatching for 122 days and subadult. There was no significant difference between the larva after hatching for 242 days and subadult. In large intestine, there was no significant difference between the larva after hatching for 122 days and the others after hatching in different stages. There was no significant difference between the larva after hatching for 242 days and subadult. 4. The distribution differences in the different organs at the same development stage were as follows: There was no significant difference between stomach and intestine of the larva after hatching for 77 days. After hatching for 122 days, there was no significant difference between stomach and small intestine and there was also no significant difference between stomach and large intestine of the larva after hatching for 122 days. But there was significant difference between the small intestine and large intestine of the larva after hatching for 122 days. There was no significant difference between stomach and small intestine of the larva after hatching for 242 days. Meanwhile, there was also no significant difference between stomach and large intestine. But there was extremely significant difference between the small intestine and large intestine of the larva after hatching for 242 days. In subadult, there was no significant difference between stomach and small intestine. There was also no significant difference between stomach and large intestine. There was extremely significant difference between the small intestine and large intestine.5. In conclusion, there was the differentiation of 5-HTIR at the early stage of postembryonic development in different organs of gastrointestinal tract in Anamnia. Meanwhile, during the development, the 5-HTIR cells increased gradually. In amphibians, the expression of 5-HTIR is higher in adult stomach and small intestine. But the expression of 5-HTIR is lower in large intestine.