Seasonal changes in plasma levels of sex hormones in the greater Rhea (Rhea americana), a South American Ratite with a complex mating system

Seasonal rhythm in sex hormones has been extensively studied in birds, as well as its relationship with the type of mating system. The Greater Rhea (Rhea americana), a South American ratite species, reproduces seasonally and has a complex mating system: female-defense polygyny and sequential polyand...

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Bibliographic Details
Published in:PloS one 2014-05, Vol.9 (5), p.e97334-e97334
Main Authors: Valdez, Diego J, Vera Cortez, Marilina, Della Costa, Natalia S, Lèche, Alvina, Hansen, Cristian, Navarro, Joaquín L, Martella, Mónica B
Format: Article
Language:English
Subjects:
17β-Estradiol
Adults
Analysis
Androgens
Animal reproduction
Animals
Animals, Zoo
Annual oscillation
Annual variations
Argentina
Biology and Life Sciences
Birds
Chromatography, High Pressure Liquid - veterinary
Ecology and Environmental Sciences
Egg laying
Eggs
Electrochemiluminescence
Endocrinology
Estradiol
Estradiol - blood
Estrogens
Female
Females
Gender differences
High performance liquid chromatography
Hormones
Hypotheses
Incubation
Liquid chromatography
Luminescent Measurements - veterinary
Male
Males
Mating
Models, Statistical
Oscillations
Parental behavior
Photoreceptors
Plasma
Plasma levels
Polyandry
Polygamy
Polygyny
Reproduction (biology)
Rhea americana
Rheiformes - blood
Rheiformes - physiology
Seasonal variations
Seasons
Sex hormones
Sexual Behavior, Animal - physiology
Signal transduction
Testosterone
Testosterone - blood
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Summary:Seasonal rhythm in sex hormones has been extensively studied in birds, as well as its relationship with the type of mating system. The Greater Rhea (Rhea americana), a South American ratite species, reproduces seasonally and has a complex mating system: female-defense polygyny and sequential polyandry. The present study aimed at analyzing the endocrine basis of reproduction in this species and its relationship with its mating system. We used HPLC and electrochemiluminescence techniques to identify and measure plasma testosterone and estradiol levels. Annual oscillations in sex hormones, testosterone and estradiol, in adult males and females were observed. Lower levels of these hormones were exhibited during the non reproductive season (February to July), whereas their maximum values were reached in September for males and November-December for females. These fluctuations reflect the seasonal changes in gonadal function. By contrast, no significant sex hormones oscillations were observed in juvenile males and females (negative control of seasonal changes). Greater rheas maintain high testosterone and estradiol levels throughout the reproductive period. The high testosterone levels during incubation and chick rearing did not inhibit parental behavior in males, which appears not to conform to the "Challenge Hypothesis". In females, the high estradiol levels throughout the reproductive season would be needed to sustain their long egg-laying period.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0097334