Sex steroid levels and leydig cell ultrastructure of the male common sheath-tail bat, taphozous georgianus

Male sheath-tail bats were collected from central Queensland over a 12-month period. Plasma testo­sterone levels peaked in August, coincident with an increase in the volume of the accessory glands and ampulla/seminal vesicle secretion. Peak spermatogenesis occurred in summer and autumn and declined in the face of maximal testosterone levels in winter. Levels of androstenedione and 5a-dihydrotesto- sterone were high compared with testosterone levels and showed no significant seasonal changes. Ultrastructural examination of Leydig cell cytoplasm revealed numerous lipid droplets and mitochondria, and an abundant smooth endoplasmic reticulum. There were no seasonal changes in Leydig cell ultrastructure. The anomalous reproductive pattern in this species is consistent with the imposition of a cold-induced winter spermatogenic shutdown, on a framework of continuous spermatogenesis, with spring peaks in testosterone and accessory gland activity

Mating-associated peak in plasma testosterone concentration in wild male grey-headed flying foxes (Pteropus poliocephalus)

Plasma testosterone (T) concentrations, measured in wild bats of P. poliocephalus in Queensland in 1983-87, showed a peak during the mating season in March. Plasma androstenedione (A) concentrations changed less dramatically with season. Mean testicular concentration and total content of T and A was substantially greater in March than in regressed testes in July-October. Paired adrenal glands were heavier during February to April than during September to November. In the same wild population, throughout a single breeding season (1987), plasma T concentrations were significantly higher in mid-March than 3 weeks previously or 3 weeks later. Testicular T content rose as the breeding season progressed, being greatest during March, coinciding with the large rise in plasma T concentrations. Testicular T concentration and content were correlated significantly with plasma T concentrations. Adrenal glands contained T, but the absolute concentrations were much lower than in the testis. No significant changes in plasma, testicular or adrenal A concentrations were found as the breeding season progressed. The large increase in plasma T during the mating season appears to be due to increased testicular production

Prolonged epididymal sperm storage, and the temporal dissociation of testicular and accessory gland activity in the common sheath-tail bat, Taphozous georgianus, of tropical Australia

Peak spermatogenic activity of the common sheath-tail bat occurs in autumn, declines over winter and ceases in spring. Accessory glands enlarge in spring when mating occurs, but are regressed at other times of the year. Spermatozoa are stored in the cauda epididymidis throughout the year, and their numbers increase progressively from early summer to late autumn. Sperm storage permits asynchrony of male and female cycles and allows each to be optimally timed in relation to environmental conditions. The temporal separation of primary and secondary sexual functions in the male enables the insemination of females close to ovulation and is a consequence of the burden of sperm storage being placed upon the male

The Effect of Cryptorchidism on the Quantitative Histology, Histochemistry and Hydrolytic Enzyme Activity of the Rat Testis

Cryptorchidism of the mature rat testis led to degeneration of the seminiferous tubules and changes in enzyme patterns and activities. Spermatogenic stages 1--4, containing pachytene primary spermatocytes in late meiotic prophase, and stage 5, containing recently formed round spermatids, were damaged by 48 h. Within 96 h stages showed a loss of germinal cells into the lumen and this was almost complete by 192 h. Acid phosphatase showed increased histochemical activity in the basal area of the seminiferous tubule up to 96 h of cryptorchidism, and at 192 h much of the activity was located in large lipidcontaining bodies within the remaining seminiferous epithelium. Total and free biochemical acid phosphatase decreased during cryptorchidism in parallel with cell loss; there were no significant changes in total cathepsin D activity but free enzyme activity was increased throughout the experimental period indicating increased lability of lysosomes in the Sertoli cell. Lactate dehydrogenase activity was mainly tubular but succinate dehydrogenase also showed interstitial activity. Lipoamide dehydrogenase (NADH) was found mainly in the interstitium. During cryptorchidism both lactate and succinate dehydrogenase activity decreased in the tubules parallel to the loss of germinal cells, whereas lipoamide dehydrogenase (NADH) activity increased in both interstitial and tubular areas. It is suggested that the initial lesion in the seminiferous epithelium, produced by cryptorchidism is in the Sertoli cell and that germ cell damage may result from reduced function of the Sertoli cell

Testicular migration, spermatogenesis, temperature regulation and environment of the sheath-tail bat, Taphozous georgianus

The testes of the common sheath-tail bat of tropical Australia undergo a seasonal migration between the abdomen and the scrotal pouches, while each cauda epididymidis is permanently maintained in the scrotal pouch. Straps of smooth muscle attach to both the cranial and caudal poles of the testes, and these extend cranially to the diaphragm and caudally to the cauda epididymidis. The testicular arteries are not coiled. Among the environmental factors investigated, maximum temperature correlated most significantly with testicular descent, and the number of spermatogonia per bat also correlated most significantly with maximum temperature. Body temperature of a captive bat ranged from 25 to 38 degrees C and this was closely related to body weight and ambient temperature. It seems likely that the scrotal pouch provides a temperature slightly below that of the body and so facilitates sperm storage in the permanently scrotal cauda epididymidis. Migration of the testes probably serves to ameliorate the seasonal temperature fluctuations to which they are exposed while the relatively high correlation between maximum environment temperature and spermatogonial numbers suggests that temperature may be a proximate influence on reproduction in the sheath-tail bat