Spatial distribution of oviposition in Rhodnius prolixus and the posible cues involved

ROLANDI, C; SCHILMAN, PE

Colonia, Uruguay

Congreso; I Latin-American Association of Chemical Ecology (ALAEQ); 2010

Latin-American Association of Chemical Ecology (ALAEQ)

Oviposition aggregation pheromones are found in a variety of insects. In some cases this pheromone is on the eggs themselves [1]. Rhodnius prolixus, an important vector of Chagas’ disease in the north of South America and a classical model of insect physiology, stick their eggs to substrates. It has already been shown that oviposition substrates modulate female`s fecundity [2], but it is not clear if there are any chemical or mechanical cues mediating the preference on a particular oviposition substrate or behavior. We tested whether R. prolixus females lay their eggs with any particular spatial distribution, and the possible cues mediating that distribution. Along 13 days, one or three females were kept in a cylindrical container with filter paper in each base, which was divided in eight equal regions and serve as oviposition substrate. Experimental groups were containers: without any chemical mark, with two regions marked with an extract of 200 eggs washed in 300 µl of di-cloromethane (DCM) and with only the vehicle (control). The number of eggs in each region was counted and the degree of aggregation was analyzed. Preliminary results show that, there is spatial aggregation of eggs, but it does not seem to be mediated by a chemical cue in DCM extracts, since there were no significant differences in the number of eggs laid in the marked and unmarked regions. Conversely, the proportion of eggs laid on the edges between the filter paper and the container were significantly higher than those laid in the central area. These results do not support the hypothesis of chemical cues guiding aggregation oviposition pattern and suggest that mechanical cues are involved. Spatial aggregation of laid eggs together with a temporal synchronicity of hatching could benefit R. prolixus reproductive success by reducing the risk of predation and deleterious effects of dehydration.