Changes in androgen concentrations during puberty and their relation to behaviour in male Saccostomus campestris (Gray 1844), an African rodent

Abstract

Sexual development in male Saccostomus campestris, the pouched mouse, was studied in terms of morphological development and changes in concentrations of plasma testosterone and androstenedione. The interaction of adult females and males following the introduction of a male was observed at all stages of the oestrous cycle. The histology of the reproductive organs is similar to that of other rodents. Measurements of the diameter of the seminiferous tubules and the width of the seminiferous epithelium suggest asymptotic growth but, although the diameter had not reached the asymptote at 70 days of age the epithelial width was close to the calculated asymptote at 55 days of age. Intraindividual variation was no greater than variation between individuals of the same age from 55-70 days. Spermatids were not seen in any animals younger than 45 days, but all animals over 55 days of age had spermatozoa in the epididymis. By 70 days of age, fertile matings were observed. At this stage, the seminiferous tubule diameter was still increasing slowly but plasma concentrations of testosterone and androstenedione had reached adult levels; at no time was the concentration of testosterone greater than androstenedione. The males were never aggressive towards females; however, they were severely attacked by females at all stages of the oestrous cycle except pro-oestrus. Only rarely did males show aggression to other males.