First assessment of persistent organic pollutants in the Greater rhea (Rhea americana), a near-threatened flightless herbivorous bird of the Pampas grasslands.

Persistent organic pollutants (POPs) are still globally distributed and can exert different effects on ecosystems. Little is known about the occurrence of these contaminants in terrestrial birds from South America. In this study, POPs were assessed for the first time in a flightless herbivorous species from the Pampas grasslands, the Greater rhea (Rhea americana). Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) were determined in 18 samples of feathers from free-ranging and captive individuals inhabiting four sites with different land uses in central Argentina. Among the 16 POPs tested in those feathers, 6 PCBs (28, 52, 101, 138, 153, and 180) and 8 OCPs (α-HCH, ß-HCH, γ-HCH, p,p'-DDE, p,p'-DDD, o,p'-DDT, p,p'-DDT, and HCB) were quantified. No PBDEs were detected. The total concentration of POPs was higher in populations living in an intensive crop production area (agriculture 159 ng g -1 and farm: 97.53 ng g-1) compared with the population in an urban area (zoo 45.86 ng g-1) and an agroecosystem with extensive rearing of livestock (cattle rearing 36.77 ng g-1). PCBs were the most abundant pollutants in all the populations studied. Lower chlorinated CB 52 and CB 101 were the principal PCB congeners detected, representing at least 70% of the total quantified. All populations studied showed a DDE + DDD/DDT ratio > 1, indicating a historical application of this insecticide. This study provides a new contribution to the scarce data on POP concentrations in South American bird species. Further investigations are needed to evaluate their potential effects on the health of individuals and populations.

State of the art knowledge in adrenocortical and behavioral responses to environmental challenges in a threatened South American ratite: Implications to in situ and ex-situ conservation.

The Greater Rhea (Rhea americana) is an endemic ratite to South America, whose wild populations have undergone a remarkable decrease due to habitat degradation and fragmentation by the expansion of the agricultural frontier, poaching and predation by dogs. Anthropogenic perturbations in wild environments, as well as the management in captivity, can generate different stress responses in this species, thus, the monitoring of adrenocortical and behavioral activities are considered primary assessment tools with both conservation and welfare implications. In this review we analyze and integrate the different measurements of glucocorticoids (in plasma, feces, and yolk) carried out in different captive and wild populations, taking into account the diverse predictable and unpredictable conditions to which the Greater Rhea responds in each of those environments. In addition, the translocation of this bird is presented as an application of stress physiology in field ecology for conservation purposes, in which we evaluated how this species responds when it is released into a novel environment. Our results indicate that this ratite has a striking high sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis compared to that of other bird species and shows a wide variety of adrenocortical responses depending on the environment in which it lives. This suggests that its HPA axis has a phenotypic plasticity that enables the rhea to cope with the environmental challenges. In this sense, we propose that one of the routes of this plasticity could be mediated by the maternal transfer of steroid hormones to the egg. Finally, we discuss the importance of integrating the monitoring of the adrenocortical response along with the environmental variables that define the life history of the species, in management and conservation programs ex-situ and in situ.

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 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.

Physiological stress in captive Greater rheas (Rhea americana): highly sensitive plasma corticosterone response to an ACTH challenge.

Up to the present no studies have been conducted either on baseline concentrations of adrenal hormones or on hormonal responses to stress in Greater rhea (Rhea americana) and most ratite species. The aims of this work were to assess the presence of corticosterone in plasma of Greater rhea, to validate a corticosterone (125)I-radioimmunoassay for determining corticosterone levels in plasma samples and to study the activation of the adrenal gland after an adrenocorticotrophic hormone (ACTH) challenge. Six captive Greater rhea juveniles of 10 months of age received an intravenous ACTH injection. Blood samples were taken at 0min (baseline pre-ACTH levels), and post-injection at 15, 30, 60min and at 24 and 48h. The high pressure liquid chromatography (HPLC) analysis of pooled plasma showed that corticosterone is the glucocorticoid found in the plasma of Greater rhea. Biochemical assays of standard validation (e.g., parallelism, exogenous corticosterone recovery) showed that measurements of corticosterone present in the plasma of the Greater rhea provided by commercial corticosterone (125)I-radioimmunoassay were accurate and precise. ACTH challenge induced a more than 40-fold increase in plasma corticosterone at 60min post-ACTH (from 4.0 to 166.5ng/ml, on average). The corticosterone response to ACTH in Greater rhea was higher than is usual in birds, an apparently typical characteristic of ratites.