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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 2x2 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. The Amazonian manatee is a threatened aquatic mammal endemic to the Amazon basin and the species is a seasonal breeder. The aim of this study was to evaluate the effect of the season on the reproductive hormone levels of captive Amazonian manatees. Different from males, all female hormones levels showed seasonal variation. The results strongly suggest the existence of reproductive seasonality in Amazonian manatees, even in captive conditions; however, apparently only females exhibit reproductive quiescence during the non-breeding season. [ABSTRACT FROM AUTHOR]

The measurement of steroid hormones (e.g., androgens, estrogens, progestins, and glucocorticoids) in alternative matrices (e.g., feces, urine, blubber, saliva, blow, milk, and ocular secretion) has been increasingly used in research with aquatic mammals. The aim of this review is to briefly summarize studies using steroid analysis in alternative matrices from captive and free-ranging aquatic mammal species. The analysis of steroid hormones from alternative matrices is a powerful tool to obtain information about reproductive biology and social behavior in free-ranging aquatic mammals, as well as to help in the management of captive animals. However, for a consistent monitoring of steroid hormones in alternative matrices, it is of crucial importance to verify if a chosen matrix and assay reliably reflects physiologic events. [ABSTRACT FROM AUTHOR]