The Seasonal Variation Of Gonadal Structure In Eurasian Tree Sparrows (Passer Montanus)

In this study, we studied the seasonal changes of behavior and gonadal structure inEurasian Tree Sparrows (Passer montanus) at lowland, temperate zone among thepre-breeding, the nest building, the first egg-laying, the first nestling, the second egg-laying,the second nestling, the pre-basic molting, and the wintering stages using ethological andhistomorphological methods. The conclusions were as follows:(1) The body weight of male sparrows in the entire breeding stages (the pre-breeding, thenest building, the first egg-laying, the first nestling, the second egg-laying, the second nestling,the pre-basic molting, and the wintering stages) was significantly lower than those fromnon-breeding stages (the pre-basic molting and the wintering stages). The body weight of themale sparrows in the second breeding stages (the egg-laying and the nesting stages) wassignificantly lower than those from the first breeding stages. The testicular volume and thediameter of spermatogenic tubules in the entire breeding stages were significantly lower thanthose from non-breeding stages. The testicular volume and the diameter ofspermatogenic tubules in the second breeding stages were significantly lower than those fromthe first breeding stages. The number of spermatogenic tubules (per unit area) in the entirebreeding stages was significantly lower than those from the non-breeding stages. The numberof spermatogenic tubules (per unit area) in the nestling stages was significantly higher thanthat in the egg-laying stage. The length of the ovary in the entire breeding stages wassignificantly higher than that in the non-breeding stages. Therefore, the seasonal changes ofgonadal structure of Eurasian tree sparrow, a typical multi-brooded bird species, duringdifferent life history stages may be the result of their adapting to the seasonal variation ofsurrounding environments.(2) The numbers of gonadal spermatognia, spermatocyte, spermatid and spermatozoon ofmale sparrows in the entire breeding stages were far more than that in the non-breeding stages.Leydig cells, had a round nucleus with a lot of lipid droplets during the entire breeding stages,and turned to fibroblasts in the non-breeding stages. There were primordial follicle, primaryfollicle, secondary follicle and atretic follicle in the ovary in the breeding and non-breedingstages. However, there were more primary follicle and secondary follicle in the breeding stages, while more primordial follicles in the non-breeding stages. These changes of thegonadal structure of Eurasian Tree Sparrow may be the morphological basis for their seasonalreproduction function.(3) The number of apoptotic cells in testicular (per unit area) was significantly higher inthe pre-breeding, the nest building and the second nestling stages than those in other stages.The apoptotic cells mainly concentrated in the peripheral of spermatogenic tubules. Thephenomenon of folliculars atresia existed in all life history stages. The apoptosis of gonad hadan important role to regulate the seasonal changes of development-atrophy of gonadal volumeand morphology. The regulation mechanism of gonadal apoptosis needed to be furtherinvestigated.