Seasonal changes in circulating testosterone and androstenedione concentration and their correlation with the anomalous reproductive pattern in the male Indian sheath-tailed bat, Taphozous longimanus

The relationship between reproductive organs, circulating testosterone, and androstenedione concentration in the male sheath-tailed bat, Taphozous lon gimanus, was studied. The masses of testis, accessory sex gland (prostate, ampullary), and epididymides showed three peaks, one each in October, Janua ry, and April. Monthly changes in testosterone also peaked during October, January, and April and closely coincided with the peak spermatogenesis. Ser um androstenedione concentration peaked during November and January. Testos terone showed a strong correlation with masses of testis and accessory sex glands, while androstenedione showed strong correlation with the body mass. Different threshold levels of testosterone may be required to trigger sper matogenesis, secretory activity of accessory sex glands and mating in Tapho zous longimanus and may be responsible for reproductive asynchrony in this species. Higher circulating concentrations of testosterone and androstenedi one throughout the year in this species, as compared with other mammalian s pecies, may be responsible for prolonged retention of sperm in the epididym ides. (C) 2000 Wiley-Liss, Inc.