The Biology Of The Seasonal Reproduction Of Chinese Skinks (Eumeces Chinensis)

In this dissertation, Eumeces chinensis distributing mainly in China, as a model animal was used to study patterns of reproductive biology of squamate reptiles. By means of microscope, ultrastructure, radioimmunity and molecular biology, I observed the relationship between seasonal changes of testes histological structure, spermatogenesis, spermiogenesis as well as the characteristics of spermatozoon; analyzed t he r elationship b etween gonadal c hanges d uring t he b reeding s eason a nd variations in plasma sex steroid hormone levels; probed the effects of ambient temperature on the recrudescence and regression of gonads; tested the influences of different ambient temperatures in the lab made on reproductive outputs of maternity and characteristics of hatchlings; analyzed the karyotypes and cloned the Sox genes of males and females to test the differences between them. The aim of the study is to clarify (1) disciplines of annual changes of male gonad, (2) clues of phylogenesis in spermatogenesis and the structure of spermatozoa, (3) endocrine mechanism in the reproductive process, (4) the maternal egg formation and reproductive output under different ambient temperatures as well as the resulting differences of hatchling phenotype, and (5) the mechanism of sex determination primarily.The main results and conclusions are summarized as the following:I. Annual variation in gonads of male E. chinensisSeasonal changes in testes, epididymides, and ductus deferens were very pronounced in E. chinensis. The largest testes were observed in March, and the smallest from May to September. Epididymides were also largest in March, but smallest from August to September. Ductus deferens were largest in April, and smallest from August to October. A rapid increase in the thickness of the germinal epithelium occurred in late September, suggesting an initiation of testicular recrudescence. After the winter dormancy, the diameter of seminiferous tubules increased steadily and reached its peak in late March, when sperms had already appeared inside the lumen of seminiferous tubules. Spermatogenesis was very active in April, but ceased soon in late May. A large number of matured sperms could be found in the lumen of ductus epididymis in late April, but none could be found in July.The wall of seminiferous tubules consisted of almost a single layer of spermatogonia and Sertoli cells in July and August. Based on descriptions by Radder et al. (2001) for the annual cycle of testicular activity of lizards, annual testicular activities of E. chinensis can be divided into six stages, including Stage I in August, Stage II from September to February, Stage III from early to mid-March, Stage IV from late March to April, Stage V from May to June, and Stage VI in July. These results, coupled with the data reported previously for adult females, showed that male and female reproductive cycles of E. chinensis were associated, as spermatogenesis and vitellogenesis initiated almost synchronically and mating activities resulting in fertilization of eggs occured only in April and May.II. The ultrastructure of spermiogenesis and spermatozoon ofE. chinensisThere were Golgi complex and mitochondrial aggregate in the early spermatids of E. chinensis, and the proacrosomal vesicle secreted by Golgi complex moved toward the nucleus; Subsequent courses of spermatid differentiation could be divided into four steps: Stage I, the nucleus formed a concavity to accommodate the proacrosomal vesicle, and acrosomal vesicle came into being. In this stage, an acrosomal grnule w as a Iso first s een i n t he d eepest p oint o f t he a crosomal v esicle, facing the center of the nuclear concavity, and the proximal centriole and flagellum appearing; S tage II, t he n ucleus e nlongates a nd p ushed t he p osterior s urface o f t he acrosomal vesicle upward giving it a flattened appearance, and chromatin condensed into fibers 1 ike s hort filaments; S tage III , t he nucleus w ent o n p rolonging a nd t he chromatin fibers changed into chromatin threads which were or...