Oocyte and ovary morphological observation of gray wolf (Canis lupus)

Abstract

Abstract The present study was carried out to describe the reproductive system of a single adult female wolf, including the uterine horns, cervix, ovaries and follicles. The cumulus oocytes complexes (COCs) and oocytes were also examined. The results showed that the size of each ovary was about 9 × 6 mm with an average of weight of 461.3 mg. The uterus was Y-shaped, and the length of each uterine horn was 14 cm. The distance from the cervix to the bifurcation of the uterine horns was also 14 cm. The left ovary had two large follicles on the surface with a diameter more than 4 mm, while the right ovary had no protuberant follicles. The ovaries were covered with a lot of fat, and were well developed. The COCs derived from the antral follicles were dark, and the nuded oocytes had a dark cytoplasm. The diameter of the oocytes removed from the antral follicles was 116.8 μm on average. The ovaries had a smooth surface and all the follicles were under the surface except for two big follicles on the left ovary. Histological examination of the ovaries by haematoxylin and eosin staining demonstrated that the primordial, primary, preantral and antral follicles were scattered in the cortex, the medulla was abundant with blood vessels. This study preliminarily reveals the features of the wolf reproductive system and the structure of its oocytes and ovaries, which might be indicative for further study and the protection of the species.