Stress-induced antioxidant defense response and body mass loss in microfilariae-infected breeding adult male village weavers ( Ploceus cucullatus )

Abstract

Studies on the impact of microfilariae does not only contribute to ecological conservation but bird-human-environmental interaction. As such, breeding and survival in the face of infections are among the ultimate goals of all species; however, this may also incur a cost of physiological or oxidative stress response when infected breeding birds must invest additional nutrients to suppress the activities of infections during breeding. We aimed to investigate how adult male breeding and non-breeding village weavers (Ploceus cucullatus) body condition, corticosterone (CORT) and superoxide dismutase (SOD) varied with microfilariae-infections during breeding period. Body condition was measured as body mass corrected for the size of adult male breeding and non-breeding birds during their breeding period. About 106 adult male village weavers were trapped at breeding, and our results suggests more 56% (33 out of 59) breeding birds were found to be infected, while 44% (26 out of 59) were not infected. In a general linear model (GLM), body mass correlated (P < 0.05) to microfilariae infection status and the interaction between infection and body size. Whereas, SOD only correlated to the infections status, and CORT concentration correlated with the breeding status of the birds during the breeding season. Based on the direction of relationship, CORT concentration was significantly higher in the breeding adult male birds during breeding, while microfilariae caused a reduction in body mass and a rise in SOD activity of the infected birds. Suggesting a poor body condition in the infected birds, and a stress-mediated antioxidant defense response that may have a long-term future implication in the breeding village weavers.