Abstract
The female reproductive cycle is modulated by internal and external signals through a complex hormone system.5 Most pinniped species are seasonal breeders where parturition and mating are highly synchronized in a 2–3 months period.1 The South American fur seal (SAFS) Arctocephalus australis, presents a seasonal reproductive cycle from November to January,3,6 but its physiology has not been studied. In the present work we describe progesterone (P4) concentration in SAFS females during the breeding season in Isla de Lobos-Uruguay related to the reproductive behavior (parturition and mating) and stage of the reproductive cycle (pregnancy and postparturition period). During an 82 day period (3 December, 2006 until 23 February, 2007) 11 females were marked, sampled and parturition and mating were recorded. Serum P4 concentration was determined by solid phase radioimmunoassay using a DPC commercial kit. This assay has been validated previously in other otariid species.4,7 Females sampled at the parturition day showed highly variable P4 concentration with an average of 6.3 ± 3.5 ng/mL, while females at 2 days postpartum had a low hormone concentration (average 0.9 ± 0.1 ng/mL). At the final stage of gestation one female had an elevated P4 concentration (22.0 ng/mL) and another female, one day post parturition, presented the highest concentration (55.4 ng/mL). Mating ranged from 3 to 7 days post parturition. Hormone concentration at parturition and peripartum period reflex the probable luteal activity at the end of pregnancy (luteolysis) and mating behavior is coincident with the early follicular phase of the estrous cycle as reported by other authors.2 In conclusion, P4 concentration showed important changes at the end of pregnancy, parturition and postpartum stages. Overall, these findings describe for the first time changes on P4 concentration related to reproductive cycle in SAFS. The present work constitutes a basic step for further studies related to pregnancy diagnosis, seasonality, embryonic diapause and reproductive success of wild South American pinniped populations.
Acknowledgements
This work was able to be completed thanks to DINARA-MGAP research permission at Isla de Lobos, fur seal keepers L. Olivera, N. Veiga, M. Casella who helped out working with animals, Dr. Ana Meikle for supporting research in wildlife physiology, König and Vetcross Laboratories who provided the anesthetic drugs and healing spray used during animal handling,Veterinaria Curupayti who provided the centrifuge for blood samples processing at the island and PEDECIBA (Programa de Desarrollo de las Ciencias Básicas-Universidad de la República) that funded hormone analysis. Special thanks to Dr. Stephanie Norman who kindly presented our poster during the IAAAM Conference.
* Presenting author
Literature Cited
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