Ovarian follicular morphometry of South American fur seal pups (Arctophoca australis).

The aim of this study was to analyze the morphometric characteristics of ovarian follicles and their distribution in the ovarian cortex in South American fur seal pups (Arctophoca australis). Samples were obtained from animals stranded in the Uruguayan Atlantic coast. Ovaries were dissected, fixed, weighed, and processed by standard histological techniques. Ovarian weight increased with pup age and body length. There was an increase in the diameter of the oocytes (22.24 ± 0.6 to 68.2 ± 5.3 µm), the nuclei (10.04 ± 0.2 to 20.7 ± 1.6 µm), and follicles (30.4 ± 1.2 to 252.6 ± 53.6 µm) of type 1 to type 5 follicles; there was a wide range of variation in the diameter of follicle type 4 and 5. Granulosa layer thickness increased between follicles type 3 and 4, whereas between type 4 and 5 there was a reduction. Thecal layer from follicles type 3 and 4 consisted of 1-2 layers of cells, whereas type 5 showed an increase in thickness (3.13 ± 0.3 to 13.8 ± 5.2 µm). Follicles type 1 and 2 occupied superficial regions within the ovarian cortex while the remaining follicles had a deeper location. These results provide a basis for comparison with females of other age categories as well as follicular dynamics studies in South American fur seals.