THE MALE REPRODUCTIVE-CYCLE OF 3 SPECIES OF AUSTRALIAN VESPERTILIONIDBAT

The male reproductive cycles of three species of vespertilionid bat (N yctophilus geoffroyi, N. major, and Vespadelus regulus) are described. Descriptions are based on the degree of testicular and cauda epididym al development estimated from field captures, and for N. geoffroyi, on histological examination of fixed specimens and assays of their testi cular testosterone concentrations. All species were found to undergo a dissociated pattern of reproduction the activity of the testes and ac cessory glands of reproduction were asynchronous. Spermatogenesis occu rred in summer/early autumn (December-March) and testes generally regr essed before mating began in autumn (March-May). Spermatozoa were stor ed in the cauda epididymides during the mating period. Leydig cells of N. geoffroyi involuted prior to mating but the prostate gland remaine d enlarged and secretory during winter (June-August), regressing in la te spring (November). Testicular testosterone concentrations were grea test when Leydig cells were maximally enlarged, and concentrations wer e low during the mating period. The reproductive cycle of all species apparently involved asynchrony between primary and secondary sexual fu nction, which is typical of vespertilionid bats inhabiting temperate l atitudes. As mating occurs when sperm stores cannot be replenished, se lection for prudent sperm allocation may be expected.