Meeting Abstract
The insects have successfully reinvaded the aquatic environment numerous times, adapting their air-filled respiratory systems to function underwater. The evolution of tracheal gills enabled insects to exploit the aquatic environment as water-breathing animals, but they all must still transform back into air-breathers when they metamorphose into flying adults. Dragonflies are developmentally amphibious insects that spend the majority of their life as aquatic nymphs, breathing water using a rectal gill, and a few months as adults, breathing air using an open tracheal system. We have begun to investigate the respiratory physiology of the water-breathing nymphs, and the physiological changes that occur during their transition to life in air. Measurements on the total CO2 content of nymph and adult haemolymph reveal that nymphs have a higher total CO2 compared to water-breathing vertebrates, but it is not significantly different to that of an air breathing adult dragonfly. The significance of these findings will be discussed in relation to the efficiency of the rectal gill as a gas exchange organ.
