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"Nichi, Marcilio"

 
 
Amaral, Rodrigo de Souza; Rosas, Fernando César Weber; Viau, Priscilla; Nichi, Marcilio; Silva, Vera Maria Ferreira da; Oliveira, Cláudio Alvarenga (detail)
   
2011
Monitoring salivary testosterone concentrations from captive Amazonian manatees (Trichechus inunguis): Is there seasonal pattern?
Reproduction, Fertility and Development 23(1): 181-181. DOI:10.1071/RDv23n1Ab156. Dec. 2010.
–ABSTRACT: Seasonality of reproduction in many nondomestic animal species appears to represent an accommodation to environmental variables, as food availability, in which influence reproductive success. Males can show a decrease of testicular size, sperm concentration, and serum concentration of testosterone because of food restriction. The Amazonian manatee (Trichechus inunguis, Mammalia: Sirenia) is a threatened aquatic mammal, endemic of the Amazon basin (South America), and is the only sirenian that occurs exclusively in fresh water. Although information is lacking about the reproductive endocrinology of free-ranging T. inunguis, they are considered seasonal breeders, with copulation and births occurring between December and July, coinciding with the increase in Amazon basin water levels and the period of most availability of food for the species (Best 1982 Biotropica 14, 76–78). Salivary steroid measurement is a noninvasive way to monitor steroid concentration, which is well correlated with the level of steroids in the serum. The aim of this study was to verify if testosterone concentrations of male T. inunguis kept in captivity, without variation of food availability, show a seasonal pattern. We used 4 adult male Amazonian manatees kept in captivity in the Laboratory of Aquatic Mammals of the National Institute of Amazonian Research–LMA/INPA, Brazil. They were fed all year with paragrass and vegetables, at not less than 8% of body weight per day. For sample collection, the pool was drained and saliva was collected from mouth mucosa using a metal spoon. Samples were collected weekly for 12 weeks in 2 periods (March–June and September–November). Salivary testosterone was measured by RIA for total testosterone using an adapted protocol previously validated for the species (Amaral et al. 2009 J. Zoo Wildl. Med. 40, 458–465) The data were analysed in a 3 × 2 factorial design, where the factors were month (each 4 weeks = 1 month) and period, using GLM test for repeated-measures. The means of salivary androgen levels were 28.80 ± 18.56 pg mL–1 and 30.77 ± 16.76 pg mL–1 for first and second periods, respectively. There were no significant main effects of month (P = 0.454), period (P = 0.607), or interaction between factors (P = 0.635). These results suggest that captive male Amazonian manatees apparently do not show reproductive seasonality. However, it is recommended to verify the existence of variation in testicular size and sperm concentration. This finding is important information for the future reproductive management of captive Amazonian manatee.
 
 
Amaral, Rodrigo de Souza; Rosas, Fernando Cesar Weber; Silva, Vera Maria Ferreira da; Nichi, Marcilio; Oliveira, Cláudio Alvarenga (detail)
   
2013
Endocrine monitoring of the ovarian cycle in captive female Amazonian manatees (Trichechus inunguis).
Animal Reproduction Science 142(1-2): 84-88. 1 tab. 1 fig. Nov. 2013.
–ABSTRACT: The Amazonian manatee (Trichechus inunguis; Mammalia: Sirenia), a threatened aquatic mammal endemic to the Amazon basin, is the only sirenian that lives exclusively in fresh water. Information about the reproductive endocrinology of the Amazonian manatee is scarce; therefore, the aim of this study was to monitor salivary progesterone and estradiol patterns during the ovarian cycle in T. inunguis. Salivary samples were collected daily during a 12-week period of two consecutive years from two captive adult females. The salivary estradiol and progesterone were measured by enzyme immunoassay. The results were analyzed in an iterative process of excluding values that were higher than the mean plus 2 standard deviations until the basal values were determined. The interval between two peaks of salivary estradiol followed by a rise of progesterone was considered as one complete cycle for the calculation of the cycle length. We observed only three complete cycles in all samples analyzed. The cycle length ranged from 42 to 48 days (mean of 44.67 days). We also observed two distinct salivary estradiol peaks during all cycles analyzed, with the first peak occurring before the rise in salivary progesterone and the second occurred followed by a return to basal progesterone levels. This is the first in-depth study of the ovarian cycle in Amazonian manatees. Our results demonstrate that salivary samples can be a useful tool in the endocrine monitoring of this species and suggest that T. inunguis shows a peculiar hormonal pattern during the ovarian cycle, a finding that may have physiological and ecological significance in the reproductive strategy of these animals.
 
 
Amaral, Rodrigo S.; Rosas, Fernando César Weber; Silva, Vera M. F. da; Graham, Laura H.; Viau, Priscila; Nichi, Marcilio; Oliveira, Claudio A. (detail)
   
2014
Seasonal variation in urinary and salivary reproductive hormone levels in Amazonian manatees (Trichechus inunguis).
Reproduction, Fertility & Development 10.1071/RD13334 Publ. online Apr. 2, 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.

Daryl P. Domning, Research Associate, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, and Laboratory of Evolutionary Biology, Department of Anatomy, College of Medicine, Howard University, Washington, D.C. 20059.
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