Sex- and seasonally related changes in plasma gonadotropins and sex steroids concentration in the European beaver (Castor fiber)
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The European beaver (Castor fiber) is the largest free-living rodent in Eurasia which belongs to the group of long-day breeders. A seasonally changing photoperiod may be related to cyclic changes in the secretion of gonadotropins and sex steroids. The goal of our study was to determine sex- and seasonally dependent changes in the concentration of gonadotropins (LH—luteinizing hormone and FSH—follicle-stimulating hormone) and steroids (T—testosterone, E2—estradiol, and P4—progesterone) in the blood plasma of free-living male and female beavers. Blood samples were collected in April—pregnancy in females; July—the end of lactation, raising of offspring; and November—sexual silence. Our results indicate that in females, a higher FSH concentration was noted in July and November than in April. Plasma T content did not differ between males and females, but in females, it was higher in April as compared with July or November. Plasma P4 concentration was the highest in females in April. In summary, our findings indicate, for the first time, that in the European beaver occur sex- and/or seasonally related changes in the concentration of plasma FSH and sex steroids (T and P4). Seasonal differences in the tested hormones can be associated with the differential activity of the hypothalamo-pituitary-gonadal axis during various reproductive stages of the beaver.
KeywordsBeaver Castor fiber Gonadotropins Sex steroids
This study was supported by the National Science Centre (project No. 2012/07/B/NZ9/01335), the Ministry of Higher Education (project No. 528/0206/882), and individual scholarships from PhD students programs (1. Author Katarzyna Chojnowska is a beneficiary of the project “Scholarships for PhD students of Podlaskie Voivodeship.” The project is co-financed by the European Social Fund, Polish Government, and Podlaskie Voivodeship, project No. POKL.08.02.02-20-002/12; 2. Author Joanna Czerwinska is a beneficiary of the project co-financed by the European Social Fund, project No. CIiTT/RIM WiM/2014/59). The authors would like to thank Jan Gozdziewski from the Polish Hunting Association in Suwalki for capturing and delivery of animals; Grzegorz Belzecki, Ph.D. from The Kielanowski Institute of Animal Physiology and Nutrition of Polish Academy of Sciences in Jabłonna and Zygmunt Gizejewski, Prof. from Research Station of Ecological Agriculture and Preservation Animal Breeding of the Polish Academy of Sciences in Popielno for cooperation and sharing of materials to research.
All experimental procedures were conducted in accordance with ethical standards of the institutional Animal Ethical Committees (ministerial approval: RDOS-28-OOP-6631-0007-638/09/10/pj and local approvals: SGGW/11/2010 and UWM/87/2012/DTN).
Conflict of interest
The authors declare that they have no competing interests.
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