The Female Reproductive-Tract of the Australian Sea Lion, Neophoca-Cinerea (Peron, 1816) (Carnivora, Otariidae)

Abstract

This first account of the morphology of the female reproductive tract of the Australian sea lion, Neophoca cinerea, is based on examination of 15 specimens. The morphology of the female reproductive tract is similar in most respects to that in other pinniped species; only features peculiar to the species are described. The Y-shaped, bicornuate uterus is for the most part septate, but has a common uterine canal that is relatively much longer than that in other otariids. The uterine mucosa of newborns is slightly hypertrophied and regresses considerably by 3 weeks postpartum. During the embryonic diapause the uterine mucosa has serrated luminal epithelium, coiled uterine glands, and tall luminal and glandular epithelia. The mucosa of the adult vagina decreases in thickness from 100-mu-m at about 2 weeks postpartum to 20-mu-m 14.5 weeks postpartum, indicative of the regressive phase typical of the delay period in other pinnipeds. The urethral meatus lacks urinary papillae, unlike most other pinnipeds. A relatively large clitoris is present, and an os clitoridis was collected from one old individual. A monoestrous cycle seemed to occur in four animals, but a polyoestrous cycle is suspected in at least one individual. Ovulation occurs from alternate ovaries in successive pregnancies. Corpora albicantia are retained for at least three breeding seasons and probably longer. Implantation occurs in the midsection of the uterine cornu, ipsilateral to the ovary that released the egg. The maximum period of embryonic diapause cannot be ascertained from the available data, although a delay of about 8-9 months is possible if the breeding cycle (pregnancy cycle) lasts about 18 months.