Behavioural responses of caddisfly larvae (Hydropsyche angustipennis) to hypoxia

The availability of aquatic oxygen can limit habitat suitability for benthic insects, and differences in hypoxia tolerance can therefore play a role in explaining distributions in the field. This study describes a behavioural test in which the trade off between different survival strategies after exposure to different oxygen concentrations is analyzed, using the caddisfly Hydropsyche angustipennis as a model organism. The impedance conversion technique was used to quantify patterns of behaviour for individual caddisflies at three levels of dissolved oxygen (100%, 50%, and 30% saturation) under controlled laboratory conditions. Exposure to hypoxia resulted in behavioural changes: under low-oxygen conditions, larvae increased their ventilation rate, which may increase oxygen uptake. However, they also increased the time spent on other activities, which may reflect avoidance behaviour.