Annual plasma testosterone cycle and ejaculatory ability in the laboratory-housed crab-eating macaque (Macaca fascicularis)

Abstract

Summary. Six fertile and healthy adult Macaca fascicularis males were studied. Radioimmunological assay of the plasma testosterone, sampled without anesthesia in the afternoon at the beginning of each month, showed an annual hormone cycle with a maximum (16.7 ! 1.1 ng/ml) in the fall and a minimum (9.5 ! 0.9 ng/ml) in the spring ( fig. 1). Using the ratio : number of ejaculations/number of trials, the ejaculatory ability of these animals ( fig. 2) was estimated for 10 min in the presence of females between days 12 and 15 of their menstrual cycle. This ability showed no cyclic variation during the year.Comparing the annual variation of testosterone levels in macaque males (Macaca mulatto, Macaca arctoides, Macaca nemestrina, Macaca fascicularis) and man, we found that, except for Macaca arctoides and Macaca nemestrina, the maximal simian levels always coincided with autumn and the minimal levels with spring in spite of the different rearing environments. (table 2).After studying ejaculatory ability and plasma testosterone level in the intact macaque throughout the year and comparing it to the results obtained by Resko and Phoenix (1972), Phoenix et al. (1973) and bVilson (1974, 1975) studying castrated males, we believe that above a minimal level, variation in the plasma testosterone level does not affect male sexual behavior, at least as far as ejaculatory ability is concerned. Moreover, du ring this study we noted that above a maximal plasma testosterone level, varying with the season, the ejaculation rate may be depressed ( fig. 3).Introduction.

Reproductive exocrine and endocrine profiles and their seasonality in male langur monkeys (Presbytis entellus entellus)

“…In the present study circannual changes in the testosterone, cortisol, and prolactin levels in langurs are similar to those reported in squirrel monkey [ 171 and man [25]. In rhesus, bonnet and cyanomologous monkeys, the testosterone levels fluctuate according to the season and mating activities [6,9,13,32]. Lack of seasonality in some of the androgen dependent parameters such as response to electro-ejaculation, testicular volume, and spermatogenesis in langurs suggested that the basal level of testosterone observed during different months of the year is sufficient to maintain the exocrine testicular functions and sexual behaviour throughout the year.…”

“…During non-breeding season the animals, either do not respond to electro-ejaculation or produce only minimal volume of semen with many abnormal spermatozoa [32]. However, no such seasonal variations in semenological parameters were reported in the bonnets, Macaca rudiata [28], Macaca fascicularis [6], and baboons [%I. In human, although a large temporal variations in the sperm concentrations found between years and within years, a general trend was noted that a higher sperm concentration during February and March and a lower sperm concentration during September [30].…”

Preliminary Report on Histological Characteristics of Male Reproductive Organs in Senile Japanese Macaques

“…There are many reports on the histological structure of the male reproductive organ as well as their seasonal changes (Kinzey, 1971;Glick, 1979). Testicular function, and annual changes of histological features have also been widely reported for Japanese macaques (Matsubayashi and Enomoto, 1983), crabeating macaques (Dang and Meusy-Dessolle, 1981) and rhesus monkeys (cordon et al, 1976;Sade, 1964;Wickings and Nieshlag, 1980;Zamboni et al, 1974). However, anatomical studies of senility of the reproductive system of non-human primates have not been published.…”