Migratory testis, spermatogenesis and reproductive cycle of the neotropical broad-eared bat Nyctinomops laticaudatus (Molossidae)

Abstract

We describe for the first time the displacement mechanism of migratory testis in Nyctinomops laticaudatus, which is little known in bats, in addition to histological analysis of its gonads. Data on testis anatomy and activity were obtained from 20 males. Males had migratory testes as they are displaced in the inguinal canals between intra and external abdominal positions. The displacement mechanism consisted of a testis ligament composed mainly of smooth muscle tissue attached to the cranial pole of the testis. Since the epididymis is closely tied to the testis, both organs are displaced together, regardless of the individual reproductive condition. Males and females showed seasonal monoestry, with a short mating period at the beginning of the dry season. The occurrence of breeding males was inversely proportional to rain and air temperature. At the mid-dry season, when air temperatures are also lower, males showed testis regressing, remaining in a reproductive hiatus for several months (rest/recrudescence) until the beginning of in the next dry season. Pregnant females were captured at the end of the dry season, and the birth of the young occurred during the rainy season, a time of greater food availability. Thus, females coordinated their reproductive phases to a more favorable period of the year for their survival and that of the offspring. Males associated their spermatogenic activity to a time of no environmental nor physiological restriction related to low air temperature.