Polietismo e expectativa de vida em operárias de Atta laevigata / Polyethism and lifespan in Atta laevigata workers

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

12/02/2010

RESUMO

Age polyethism is the change in activities carried out by members of a colony during its life. Older individuals have lower future value to the colony, so it would be better for the colony if they could perform more dangerous tasks outside the nest and not return to its interior. Thus, the risk of bringing pathogens into the colony is reduced, protecting internal individuals and thereby increasing the life expectancy of the colony. The first hypothesis of this study is that external ants are older than internal ones and therefore die earlier. A complementary hypothesis is that external workers are weaker, having been previously selected by the colony to carry out dangerous tasks, since the losses would be less prejudicial to the colony. To test these hypotheses, internal e external workers of the leaf-cutter ant Atta laevigata (Smith) (Hymenoptera: Formicidae) were collected from nests in the field (Viçosa, Minas Gerais State, Brazil) and also from laboratory colonies. Ants of the same size were placed individually in Petri dishes and supplied with water and honey solution 1:1. To test the second hypothesis, ants were inoculated with the fungus Beauveria bassiana (Bals.) Vuill to compare their survival to controls. In both the field and laboratory experiments, the external workers died before the gardeners, suggesting that they are older, supporting the first hypothesis, that this species use age-dependent polyethism. In the experiment with ants from the field, there was no difference in the survival curves of external ants, inoculated or not. There was a difference in the laboratory ants. The first experiment indicates that external workers are not previously weaker, but the second suggests they are. This could be the difference betweennatural conditions (where they have more contact with pathogens so more susceptible individuals may be eliminated) and laboratory conditions (less pathogens). This study is the first step to test the conveyor belt model of Schmid-Hempel. Additional studies will be important to understand the intrinsic and extrinsic mechanisms mediating progression from internal to external activities, during aging.

ASSUNTO(S)

polietismo temporal insetos sociais atta beauveria bassiana ecologia polyethism temporal social insects atta beauveria bassiana

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