Ovarian morphology of the dusky leaf monkey (Presbytis obscura): follicular development and atresia.

The ovarian morphology and the pattern of follicular development and atresia have been described for the dusky leaf monkey, Presbytis obscura, on the basis of a study of material from 44 female monkeys collected at various stages of the menstrual cycle, pregnancy and lactation. Marked differences were found in the dimensions of many ovarian components between this monkey and the other species of langur previously described. During follicular development the oocyte increased in diameter from 28 micrometer in the primordial follicle to a maximum of 85 micrometer in a pre-ovulatory follicle measuring 8.0 x 4.0 x 7.0 mm. The majority of developing follicles, however, underwent atresia with the theca interna transforming into interstitial tissue. Although present in the follicular phase of the menstrual cycle, this tissue was most pronounced during early pregnancy, at a time when lutealisation also occurred, resulting in the formation of corpora lutea atretica. These findings have been discussed in relation to other catarrhine primates.