The Study On Cell Apoptosis And Related Proteins During Spermatogenesis Of Reticulitermes Aculabialis

Termites are the oldest social insects in the world, with a very wonderful and complex caste differentiation. Termite's grade decision does not depend on the genetic characteristics of fertilized eggs. The fertilized eggs do not contain particular factors which determine the caste differentiation. The phenomenon of caste differentiation appears after the egg stage, as it does like the bees, called "non-genetic polymorphism". The occurrence of germ cells is very important in the insect life cycle stage, especially in the social insects, the phenomenon shows a especial survival strategy in the colony. In recent years, hormonal regulate germ cell development and thus the caste differentiation of social insects are more reported, while the role of apoptosis and its related proteins are less reported. In this paper, we use one of the most harmful termite----Reticulitermes aculabialis as the research material, compared the productives'gonad and germ cells with non-productives'by microscopic histology and immunohistochemistry methods.In order to explore the regulation of different termite castes' fertility differentiation we have studied the role of apoptosis and its related proteins Bcl-2 and Bax during spermatogenesis. The results are as follow:1. The comparison of germ cell number between reproductives and non-reproductivesReproductives and workers have complete spermatogenesis process, including spermatogonia, primary spermatocytes, secondary spermatocytes, spermatid and sperm. The both format sperm in the testis, while soldiers only have spermatogonia, primary spermatocytes and secondary spermatocyte stages, no spermatid and sperm stages. The research of this part is about the comparation of the germ cell total number among reproductive, worker and soldier and the comparation of the germ cell number during the same period among the three castes. As a result, the total number of germ cell in adult reproductive testis was about 3903±357; the total number of last instar nymphs was about 2492±238; the number of germ cell in the testis of mature worker amount to 2175±209; the number of germ cell in soldier testis only 174±18, sharply less than other castes. The ratio of the total number among different castes were:adult reproductive:the last instar nymph=8:5; adult reproductive:mature worker=9:5, the last instar nymph:mature worker=11:10, worker:mature soldier=25:2.The total number of germ cell showed significant differences among different castes. The comparison of germ cell number in different stages of reproductive, worker and soldier testis showed a significant difference. proving Reticulitermes aculabialis'reproductive ability differentiation firstly reflected on the number difference of germ cell which can reflect the degree of gonadal development, thereby affecting the differentiation of reproductive ability. From the study of germ cell number between different worker ages found the germ cell number of the mature worker was significantly higher than the others'. Young worker's gonadal development is restrained. But in certain circumstances young worker's testis can largely developed, indicating that worker has the potential ability for further development.2. Apoptosis during reproductive, worker and soldier spermatogenesisThere is apoptosis during reproductive, worker and soldier spermatogenesis, and mainly occured in spermatogonia, primary spermatocytes and spermatid stages. Compared with reproductive, worker's germ cell apoptosis rate was significantly higher, indicating that worker's gonad more degenerated than reproductive's, but worker can form sperm during spermatogenesis, suggesting that worker has the potential ability of developing into supplymentary reproductive termite. Soldiers only have spermatogonia, primary spermatocytes and secondary spermatocytes stages, no spermatid and sperm stages, and the apoptosis rate of each period was significantly higher than the same period germ cell of other castes'. This indicated that soldier's gonad was extremely degenerated and didn't have the potential ability to develope into supplymentary reproductive termite.3. Germ cell apoptosis and related proteins-Bcl-2-like and Bax-likeBoth reproductives and workers have the Bcl-2-like positive expression. Compared to adult male termite, Bcl-2-like positive expression rate in spermatogonia of last instar nymphs and mature worker performance a very significant difference. In worker testis only secondary spermatocytes express high rate of Bcl-2-like, the primary spermatocyte, spermatid and sperm have lower Bcl-2-like expression than reproductives. Both reproductives and workers have the Bax-like positive expression. The Bax-like positive expression rate of spermatogonia, secondary spermatocytes, spermatid and sperm in worker's testis was significantly more than the same period germ cell of reproductives. Particularly, the Bax-like positive expression rate of sperm was significantly increased. It suggests that a large number of sperm was dead in worker's testis. Maybe it is an important reason for worker's sperm have no fertility. Bcl-2-like is apoptosis inhibitor, Bax-like is pro-apoptotic factor, the ratio of the two decide a cell's fate. From the study of the ratio between Bcl-2-like and Bax-like we found that in worker's testis there was a large number of germ cell progressed apoptosis. This part provides a further evidence for worker's lower reproductive ability on molecular level.In conclusion, we found the reproductive ability differentiation among reproductives, workers and soldiers was affected by their germ cell number and proved that apoptosis, Bcl-2-like and Bax-like were exactly existing during spermatogenesis. The workers do not have the reproductive ability, while when the colony needs, worker can transform into supplementary reproductives to maintine the colony's stibility. We also set a theoretical foundation on the study of caste differentiation from apoptosis level.