关键词: 高原鼢鼠, 季节性繁殖, 精子发生, 睾酮, 维甲酸, 精原细胞

Abstract: Seasonal reproduction is a life history adaptation that helps animals survive under the changes of their environments. Seasonal reproduction is tightly regulated by the hypothalamus-pituitary-gonad (HPG) axis. Plateau zokor (Eospalax baileyi) is an underground rodent native to the Qinghai-Tibet plateau and they breed only in April to July. How gametogenesis and reproductive activities are regulated in underground mammals remains largely unclear. In the present study, we showed that spermatogenesis in adult male plateau zokor was seasonally regulated. Seminiferous tubules of plateau zokor contained well-developed germ cells including elongated sperm during breeding season (April to June). Based on the cell association and morphological features, the seminiferous epithelium can be divided into 10 stages. During non-breeding season, seminiferous tubules only contained spermatogonia and Sertoli cells, indicating spermatogenesis had been arrested. Levels of gonadotropin-releasing hormone, luteinizing hormone and testosterone were significantly increased in breeding season with notable reduction of melatonin (P < 0.05), while follicle-stimulating hormone level did not show a significant change. Further analysis revealed that biogenesis of retinoic acid, responsible for spermatogonial differentiation, was changed dramatically. As expected, supplementation of retinoic acid induced resumption of spermatogenesis in reproductively dormant animals. Together, these data demonstrated morphological features and key regulatory factors of seasonal spermatogenesis in plateau zokor. This study can provide a reference for understanding similar mechanism existed in other underground rodents.

Key words: Plateau zokor, Seasonal reproduction, Spermatogenesis, Testosterone, Retinoic acid, Spermatogonia