REPRODUCTION IN THE MALE STOAT, <i>MUSTELA ERMINEA</i>

Abstract

Summary. The male stoat has a well-defined breeding season extending from May until the end of July. The testis then regresses rapidly and remains in quiescence until the end of November when the seminiferous tubules consist of a peripheral layer of supporting cells and occasional spermatogonia. The onset of spermatogenesis in December is marked by the appearance of primary spermatocytes and, by April, most of the tubules contain germinal cells in all stages of spermatogenesis. Spermatozoa are not found in the cauda epididymidis until May. Juvenile males, unlike the females, attain sexual maturity in the spring following the year in which they were born. Testosterone concentrations of plasma samples obtained from adults at intervals throughout the year were determined by gas-liquid chromatography. Levels rose with the onset of spermatogenesis and reached a maximum during March and April. They decreased in May but another smaller peak developed during June and July corresponding to the mating period. This peak may be related to maintenance of the accessory sex organs and libido.