Male reproductive cycle of the toad Bufo melanostictus in Taiwan

The male reproductive cycle of the toad, Bufo melanostictus, was studied with emphasis on spermatogenic activity, plasma androgen, and changes in the weights of testes, liver, and fat bodies. A total of 98 toads were collected between March 1990 and March 1991 in central Taiwan. Histological evidence indicated that the spermatogenic cycle of this toad is of a fluctuating continuous type. Although cell nests of all spermatogenic types were present every month of the year, the greatest intensity of spermatogenic activity, as expressed by the presence of sperm bundles, occurred in March. Both testicular weight and plasma androgen levels peaked in March. The weights of fat bodies peaked in July, which was not coincident with the beginning of breeding. Combined data from spermatogenic activity, plasma androgen levels, and changes in the weights of testes, fat bodies, and livers revealed that B. melanostictus is a continuous breeder. However, its annual reproductive cycle could be divided into 4 periods: 1) breeding period (February-April); 2) postbreeding period (May-June); 3) reproductive energy preservation period (July-September); and 4) torpid period (October-January).