Early primary-rather than primordial follicles constitute the main follicular reserve in the African elephant (Loxodonta africana)

Abstract

Information on the ovarian follicle reserve in the African elephant (Loxodonta africana) is lacking. This study set out to determine the ratios of early preantral follicles and their relative dimensions in the ovaries of 16 African elephant aged 10–34 years. The ovaries were sectioned histologically. Follicles were counted and classified according to expansion of the pre-granulosa cells. Early primary follicles were the most common (75.8% ± 11.8%), followed by true primary follicles (23.8% ± 11.8%), whereas primordial follicles were the most rare (<2%). Measurements made on at least 100 early preantral follicles from each animal (n = 1464) indicate that growth in oocyte and nuclear diameters started with transition to the true primary stage P < 0.01. This, together with the observed ratios between the three types of early preantral follicles suggest that both classical primordial and early primary follicles contribute to the ovarian reserve in the African elephant.