Seasonal variation in urinary and salivary reproductive hormone levels in Amazonian manatees (Trichechus inunguis)
Rodrigo S. Amaral A B D , Fernando C. W. Rosas B , Vera M. F. da Silva B , Laura H. Graham C , Priscila Viau A , Marcilio Nichi A and Claudio A. Oliveira A
+ Author Affiliations
- Author Affiliations
A Faculty of Veterinary Medicine and Animal Science, University of São Paulo – USP, São Paulo, SP 05580-270, Brazil.
B Laboratory of Aquatic Mammals, National Institute of Amazonian Research – INPA, Manaus, AM 69060-001, Brazil.
C Department of Animal and Poultry Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
D Corresponding author. Email: rsamaral@gmail.com
Reproduction, Fertility and Development 27(7) 1065-1071 https://doi.org/10.1071/RD13334
Submitted: 1 October 2013 Accepted: 7 March 2014 Published: 2 April 2014
Abstract
The Amazonian manatee (Trichechus inunguis) is a threatened aquatic mammal endemic to the Amazon basin. The aim of this study was to evaluate the urinary and salivary reproductive hormone levels of captive Amazonian manatees collected during two seasons of the year. Salivary samples from four males and urinary and salivary samples from three females were collected during two seasons (March–June and September–November) over two consecutive years. Salivary testosterone in males was measured by radioimmunoassay and reproductive hormones in females (salivary progesterone and oestradiol and urinary progestogens, oestrogens and luteinising hormone) were measured by enzyme immunoassay. The data were analysed in a 2×2 factorial design, where the factors were year and season. There was no effect of year or season for salivary testosterone. All female hormones showed a seasonal effect (higher hormone levels during March–June than September–November) or an interaction between year and season (P < 0.05). These results strongly indicate the existence of reproductive seasonality in Amazonian manatees; however, apparently only females exhibit reproductive quiescence during the non-breeding season. Further long-term studies are necessary to elucidate which environmental parameters are related to reproductive seasonality in T. inunguis and how this species responds physiologically to those stimuli.
Additional keywords: reproduction, saliva, sirenian, steroids, urine.
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