Progesterone and oestradiol-17 beta concentration profiles throughout the reproductive cycle in harbour seals (Phoca vitulina).
Serum samples of harbour seals kept in captivity were analysed for progesterone and oestradiol-17 beta. The hormone profiles obtained were used to describe a complete reproductive cycle. A clear peak in oestradiol values, indicative of ovulation, was followed by elevated concentrations of progesterone. Implantation probably occurred 3-3.5 months thereafter. Progesterone concentrations rose significantly in the last 3-4 months of gestation, whereas oestradiol concentrations gradually increased after implantation. Lactational oestrus was marked by a peak of oestradiol on average 25 days after parturition and lactation lasted 4-5 weeks. Previous pregnancy had a marked influence on the timing of oestrus; females with offspring started a new reproductive cycle about 14 days later than previously non-pregnant seals. No differences in timing of parturition between the 2 groups were observed. This was probably the result of a flexible period of delayed implantation.
Reijnders
P J
PJ
Research Institute for Nature Management, Dept. Estuarine Ecology, Den Burg, The Netherlands.
D000818:Animals; D010065:Embryo Implantation, Delayed / Q000502:physiology; D004958:Estradiol / Q000097:blood*; D005260:Female; D007774:Lactation / Q000097:blood; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D012098:Reproduction / Q000502:physiology*; D046048:Seals, Earless / Q000097:blood*; D012621:Seasons
D011374:Progesterone; D004958:Estradiol