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

An updated look at the mating system, parental care and androgen seasonal variations in ratites

Androgens modulate multiple key aspects of male reproduction, from morphology to mating behavior. Across animals the seasonal patterns of androgens are tightly linked to many of the species' life-history traits and their evolution. One popular framework to address this issue has been the Challenge Hypothesis, which proposed a testosterone-mediated trade-off between mating and parental care in males. Given the lack of empirical support, especially in birds, this hypothesis has been recently revisited (Challenge Hypothesis 2.0), integrating aspects such as male-female interactions and the diversity of reproductive systems in birds. Ratites constitute the most basal avian group (Palaeognathae: ratites together with Tinamiformes) and have certain characteristics that make them unique. They are flightless and generally have promiscuous mating systems with communal nests and male-only parental care (nest building, incubation and chick rearing). Furthermore, male testosterone concentrations remain high during the entire parental care period. Here we review the reproductive biology of ratites, integrating information on seasonal variations in parental care, social interactions and androgen levels across the group, in light of the Challenge Hypotheses and the Challenge Hypothesis 2.0 (there are no seasonal hormonal data for Tinamiformes, therefore they are not included in this review). We also discuss the constraints that could explain the lack of experimental approaches in behavioral endocrinology across ratites. I hope this review will motivate further research on this basal group of birds and further our understanding of the evolution of the mechanisms in the endocrine system that underly reproductive behavior across birds.

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, β-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.

Genetic identification of the ciliates from greater rheas (Rhea americana) and lesser rheas (Rhea pennata) as Balantioides coli

The ciliate species Balantioides coli can be cross-transmitted between humans and several animal species. Usually harmless, sometimes it can be pathogenic and cause the death of the host. In birds, B. coli has been confirmed in ostriches by genetic analysis, but the identification from South American greater rheas (Rhea americana) and lesser rheas (Rhea pennata pennata) is tentative. Since these species are reared for commercial purposes and for reintroduction into the wild, it is necessary to elucidate whether the ciliate from rheas is B. coli to minimize health risks for humans and for other domestic and wild animals. Individual parasite cells are collected from Argentinean isolates of reared greater rheas and of wild and reared lesser rheas, and their ITS region was PCR amplified; the cloning products were sequenced and compared with sequences available in public databases. The results have shown that several sequence types are expressed at the same time in the parasite cells, and all correspond to B. coli, confirming the possibility of cross-transmission of the parasite between wild and reared South American rheas and several mammal species and humans.

Effect of maternal environment on yolk immunoreactive corticosterone and its influence on adrenocortical and behavioral activity in chicks of Greater Rhea (Rhea americana)

Maternal corticosterone in avian eggs may modify offspring phenotype in order to increase survival in poor environments. In the Greater Rhea (Rhea americana), we previously found that yolk immunoreactive corticosterone is influenced by the quality of the maternal environment: eggs laid by females of the intensive rearing system (IRS), living in poor captive conditions, had higher yolk immunoreactive corticosterone than those produced by females of the semi-extensive rearing system (SRS), living in better conditions. Here, we evaluate if these different hormone levels are associated with the production of different phenotypes. We collected eggs from the IRS and SRS for hormonal quantification and artificial incubation. Then, half of the chicks selected from each environment were exposed to a capture and restraint protocol, and the rest remained undisturbed and were used as controls. In the IRS, we found that higher yolk immunoreactive corticosterone was associated with the production of chicks that had reduced hatchability, lower hatchling mass and higher baseline fecal glucocorticoid metabolites (FGM) than those produced by SRS females. Moreover, after capture and restraint, IRS chicks did not modify their FGM nor their behaviors compared to their controls, while SRS chicks increased their FGM and spent more time ambulating and less time pecking, compared to their controls. These results indicate that yolk immunoreactive corticosterone could modify offspring phenotype. Although future studies are needed to elucidate their implications for fitness, our results suggest that yolk corticosterone could be mediating an adaptive maternal effect that allows individuals to better cope with poor conditions.