Study On Reproductive Biology And Artificial Breeding Of Xenopus Tropicalis

Amphibia is the bridging species between terrestrial animal and aquatic animal and therefore it plays a very important role in the study of biology and is a significant species studying organism evolution. Xenopus tropicalis, as one model organism, possesses many predominant characters which are consisted of strong life, fast growth, external fertilization, in vitro development, short immature stage, high fecundity and whole visible embryonic development. Thus X. tropicalis is considered as an important study object of development biology, molecular biology and cytobiology. At present, it is widely used in the study of embryonic development, functional genomics, human hereditary disease and animal disease model.In this paper, the artificial breeding and reproductive biology of X. tropicalis was discussed. And the study of breeding was separated into the following three parts.The first part: The introduction and establishment of X. tropicalis rearing system. In this part, three different artificial rearing facilities were established for different development stages of X. tropicalis. And the optimal artificial rearing environment were:22℃～28℃,PH6.5～8.5,DO>5.0mg/L,NH₄-N<0.05mg/L,NO₂-N<0.01 mg/L,Cl-<3μg/L,150～250mg/L of water hardness.The second part: Based on the method of histology, the microtome section of spermary and ovaries at each development stage of X. tropicalis were made by paraffin slicing and HE staining, in order to clarify the development law of genitical gland of X. tropicalis. The results showed that the testis somatic index and the ovary index nearly reached the peak at the same time. And the spermary development of X. tropicalis could be separated into 5 stages, namely stage I, II, III, IV, V. While the ovaries development of Xenopus tropicalis could be separated into 6 stages. They are ovogonium hyperplasy period, oocyte growing period, transition stage of oocyte growing period, period of vitellogenesis and period of yolk obturation belonging to the 4th stage, period of oocyte nuclei dissymmetry, period of after parturited ovaries.Moreover, comparing the monthly cycle change of the ovary index with that of the testis somatic index, we found that the male and female X. tropicalis sexually matured almost at the same time after about six months growth of the gonads. Meanwhile, the ovary index and testis somatic index reached the maximal values and both of them increased with the increasing weight and length. The linear regression functions were as follows: the regression function of length and the testis somatic index of male X. tropicalis was y = 6.57x + 1.788, R2 = 0.9644; the regression function of weight and the testis somatic index of male X. tropicalis was y = 32.674x + 0.9143, R2 = 0.9407; the regression function of length and the ovary index of female X. tropicalis was y = 0.091x + 2.6516, R2 = 0.9092; the regression function of weight and the ovary index of female X. tropicalis was y = 0.5119x + 4.5476, R2 = 0.9083.The third part: We studied the embryo development process of X. tropicalis by method of photomicrograph. The results showed that the embryo development process was divided into 26 periods and the duration of the process was about 56.89±2.2 hours at 26℃.