Metabolism and water loss rate of the haematophagous insect, Rhodnius prolixus: effect of starvation and temperature

Abstract

Abstract Haematophagous insects suffer big changes in water needs under different levels of starvation. Rhodnius prolixus is the most important haematophagous vector of Chagas disease in the north of South America and a model organism in insect physiology. Although, there are some studies on patterns of gas exchange and metabolic rates, there is little information regarding water loss in R. prolixus. We investigated if there is any modulation of water loss and metabolic rates under different requirements for saving water. We measured simultaneously CO2 production, water emission and activity on individual insects in real time by open-flow respirometry at different temperatures (15, 25 and 35°C) and post-feeding days (0, 5, 13 and 29). We found: 1) a clear drop in the metabolic rate between 5-13 days after feeding that cannot be explained by activity and 2) a decrease in water loss rate with increasing starvation level, by a decrease in cuticular water loss during the first 5 days after feeding and a drop in the respiratory component thereafter. We calculated the surface area of the insects and estimated cuticular permeability. In addition, we analyzed the pattern of gas exchange; change of cyclic to continuous pattern was affected by temperature and activity, but it was not affected by the level of starvation. Modulation of metabolic and water loss rates with temperature and starvation could help R. prolixus to be more flexible in tolerating different periods of starvation, which is adaptive in a changing environment with the uncertainty of finding a suitable host.