Histology of reproduction in harp and grey seals during pregnancy, postparturition, and estrus

Abstract

Reproductive tracts were collected on the eastern coast of Canada from adult female grey seals (Halichoerus grypus) during gestation and postparturition, and from adult female harp seals (Phoca groenlandica) during delayed implantation and postparturition. Reproductive tracts were fixed in 10% buffered formalin for light microscopy. The placental site and adjacent tissue were preserved in 2% glutaraldehyde – 1% paraformaldehyde for scanning electron microscopy. During the delay of blastocyst implantation, the endometria of the gravid and nongravid uterine horns were similar in microscopic appearance. During gestation, maternal septa were often surrounded by maternal epithelium deep into the placental labyrinth except distally, where the maternal cells were replaced by syncytium. Marginal hematomas increased in size and complexity throughout placentation. Following parturition, uterine regression occurred earlier in harp seals (10 days postpartum) than in grey seals (21–25 days postpartum). Postpartum changes were most pronounced in the placental site where the blood vessels underwent extensive reorganization. In some specimens, the extensively vascularized placental site of the previous pregnancy was still apparent 12 months later. Epithelial replacement in the uterus was complete in grey seals 21–25 days postpartum and sooner in harp seals. Cervical and vaginal stratification occurred in both phocids following parturition and increased towards estrus. A recently ovulated grey seal was obtained between 21 and 25 days postpartum. The vaginal stratification and the presence of sperm in their uterine horns indicated that grey seals began estrus about 12–17 days postpartum. In harp seals, estrus appeared to occur towards the end of the lactational period, about 10–12 days postpartum.

Determining Pregnancy From Blubber in Three Species of Delphinids

“…Nevertheless, this female's progesterone levels were already down to 30% of the lowest level we observed for L. borealis carrying a fetus. In most mammals, after normal parturition, the uterus regains prepregnancy state within a short period (Henell et al 1983, Ouellette and Ronald 1985Katila 1988, Dolezel et al 1991). For example, in cattle, uterine morphology returns to non‐gravid shape within ten days postparturition (Dolezel et al 1991).…”

Growth and seasonal fluctuations in size and condition of male Northwest Atlantic harp seals Phoca groenlandica: an analysis using sequential growth curves

“…Late February can therefore be considered the beginning of the rut in male harp seals from this population. Yet most females mated after March 19, after they had completed their 12 d nursing period (Kovacs & Lavigne 1985, Ouellette & Ronald 1985, Sivertsen 1941, Sergeant 1991. Thus males are in the rutting state and reduce their feed intake about 3 wk before most copulations take place, probably to insure that they can service females that whelp early or barren females that may come in estrus before reproducing females.…”

Decline in the Pregnancy Rate of Baltic Grey Seal Females during the 2000s

“…In cases when CA and the placental scar were on opposite sides (usually they are on the same side, Atkinson 1997) or when there were signs of scars in both uterine horns, mainly concerned older females. In multiparous females, one can sometimes see signs of placental scars from earlier years (Ouellette & Ronald 1985), which may result in overestimates of the pregnancy rate. However, pregnancy rate on the basis of placental scars/CA in spring and that based on fetuses in autumn did not differ significantly.…”