ABSTRACT
Glucocorticoid hormones play a key role in day-to-day adjustments to fluctuating metabolic needs. These hormones also mediate physiological and behavioral responses to stressful events, allowing individuals to cope with stressors. Various environmental insults, such as a food shortages, predation attempts, and agonistic encounters often elevate plasma glucocorticoid levels in vertebrates. Because exposure to maternally-derived (via circulation or egg) glucocorticoids may be detrimental to the developing embryo, maternal stress can have negative carryover effects on offspring fitness. We examined corticosterone, the primary avian glucocorticoid, concentrations in egg yolk in a plural-breeding, joint-nesting species, the smooth-billed ani (Crotophaga ani), in which females compete among themselves to lay eggs in the final incubated clutch. We investigated whether yolk corticosterone levels varied with laying order and group size. Because egg-laying competition leads to physiological and social stress that is intensified with group size and laying order, we predicted that yolk corticosterone levels should increase from the early to the late egg-laying period and from single female to multi-female groups. In this two-year field study, we found that yolk corticosterone levels of late-laid eggs within the communal clutch were higher in multi-female groups than in single female groups. Results from this study suggest that laying females experience higher levels of stress in multi-female groups and that this maternal stress influences yolk corticosterone concentrations. This study identifies a novel cost of group-living in plural-breeding cooperatively breeding birds, namely an increase in yolk corticosterone levels with group size that may result in detrimental effects on offspring development.
Subject(s)
Birds/physiology , Corticosterone/blood , Egg Yolk/physiology , Animals , Breeding , Female , RadioimmunoassayABSTRACT
Os nematóides do gênero Dispharynx (Railliet, Henry & Sisoff, 1912) parasitam aves de diversas ordens e têm sido estudados, principalmente, em aves de importância econômica devido às lesões que provocam no proventrículo dos hospedeiros. Dispharynx nasuta (Rudolphi, 1819) Stiles & Hassall, 1920 é registrado em duas espécies de Cuculiformes, anu-branco, Guira guira Gmelin, 1788 e anu-preto, Crotophaga ani Linnaeus, 1758, no Sul do Brasil. Entre 2005 e 2008 foram coletados e necropsiados 120 espécimes de G. guira e 120 espécimes de C. ani nos municípios de Cacequi, São Vicente do Sul e Jaguari, Rio Grande do Sul, Brasil. A prevalência de D. nasuta foi de 28,3% em G. guira e 26,7%, em C. ani, e a intensidade média de infecção foi de 8,81 (DP=18,41; Amplitude 1 - 82) helmintos/hospedeiro, em G. guira, e de 5,10 (DP=6,17; Amplitude 1 - 30) helmintos/hospedeiro, em C. ani. Já a abundância média de infecção foi de 2,28 (DP=10,02) helminto/hospedeiro, em G. guira, e de 1,32 (DP=3,82) helminto/hospedeiro em C. ani. Análise comparativa entre o sexo, a maturidade sexual e a estação do ano, para as duas espécies de aves, mostrou que em C. ani não ocorreram diferenças significativas com relação a qualquer dos parâmetros analisados. Em G. guira as fêmeas estavam mais parasitadas do que os machos (P=0,039); as fêmeas encontravam-se mais parasitadas no inverno (P=0,008); os machos, no verão (P=0,011); os machos jovens estavam mais parasitados do que os adultos (P=0,015). As lesões encontradas no proventrículo das aves parasitadas confirmaram o diagnóstico de hiperplasia adenomatóide do proventrículo com proventriculite granulomatosa. Esta comunicação amplia o número de espécies hospedeiras e a distribuição geográfica do nematóide D. nasuta.
Nematodes of the genus Dispharynx (Railliet, Henry & Sisoff, 1912) are parasites of several groups of birds which have been primarily studied in birds of economic importance due to the injuries caused in the host proventricle. Dispharynx nasuta (Rudolphi, 1819) Stiles & Hassall, 1920, was found in two species of Cuculiformes, guira cuckoos, Guira guira Gmelin, 1788 and smooth-billed ani, Crotophaga ani Linnaeus, 1758, in the southern-most State of Brazil. From 2005 to 2008, 120 specimens of G. guira and 120 specimens of C. ani, were collected in Cacequi, São Vicente do Sul and Jaguari, Rio Grande do Sul State, Brazil. The prevalence of D. nasuta in G. guira was 28.3% and in C. ani 26.7%; the average intensity of infection was 8.81 (DP=18.41; Amplitude 1 - 82) helminths/host in G. guira and 5.10 (DP=6.17; Amplitude 1 - 30) in C. ani; the average abundance of infection was 2.28 (DP=10.02) helminths/host in G. guira, and 1.32 (DP=3.82) in C. ani, respectively. Comparative analysis between the species, sex, sexual maturity and seasonality showed that C. ani did not present significant differences with regard to any of the analyzed parameters. Guira guira presented some differences: females had more parasites than males (P=0.039); female birds collected in the winter (P=0.008) and male birds collected in the summer had more parasites (P=0.011); and immature males had more parasites than adult males (P=0.015). The injuries found in the proventricle of the parasitized birds were compatible with adenomatoid hyperplasia and with granulomatosis proventriculitis. This communication expands the number of host species and the geographic distribution of D. nasuta.
