O transporte de carga por Acromyrmex subterraneus: investigação do efeito da marcação química e da atividade individual

Abstract

Cutting ant workers collect fresh plant fragments, which are used as substrate for the cultivation of the symbiotic fungus. The diet of cutter ant workers, especially offspring, consists of the consumption of the fungus symbiont, which makes foraging a prime activity for the success of their colonies. Thus, the mass of the plant fragment transported to the colony is directly related to the success of the foraging, since this interferes in the speed of the workers' movement and in the feeding of the colony. To identify the factors that can modulate the determination of the load carried in leaf cutting ants, it was evaluated how the trail pheromone influences the determination of the vegetal fragment carried by the workers of Acromyrmex subterraneus. At the same time, there was interference of the chemical signal in the flow of workers, as well as the load carried in the displacement speed. Using a trail with prior chemical marking at the beginning of foraging, no variation of the transported vegetable mass was recorded, however, there was a reduction in the flow of workers leaving the colony and those returning without carrying cargo, as well as the speed of movement of workers with load. Since the pheromonal chemical track interfered with the flow of workers along the foraging trail, it is assumed that the determination of the transported load may be related to the interactions between the workers. In the second experiment, it was investigated whether the individual activity of the forage of Acromyrmex subterraneus influences the determination of the transported plant fragment. By observing individually tagged forages during the same foraging event, the number of trips carried out carrying vegetable fragment was recorded, in which it was verified that the individual activity of the forage did not interfere in the transported foliar mass, that is, the mass of the transported vegetable fragment was the same independent of the number of trips made by the same worker. It was also recorded that most of the workers had carried out up to three trips, being therefore most of the transport of leaves realized by workers who do not exclusively perform the foraging activity, which are denominated of non-elite workers. Suggesting a colony's collective effort to ensure foraging success. In this way, the physical factors, for example, the relation between worker size and fragment and the mechanisms of collection and obtaining of resources are included, the interactions between the individuals of the colony, which are fundamental for modulation of the transported vegetal load by the workers.