Philip Matthews

Research in my laboratory focuses on understanding the respiratory adaptations of animals, primarily insects. During their 400 million year evolutionary journey, the insects have become the most abundant and diverse of all animals, among the first to invade the land and the first to evolve flight. Much of their success can be attributed to a highly efficient respiratory system, capable of functioning in environments where oxygen is scarce (e.g., underwater and in decomposing material) and when extreme demands are placed on oxygen supply (e.g., during flight). I am particularly interested in those insect groups that have re-adopted an aquatic lifestyle, evolving various gas-exchange strategies. These range from snorkels and siphons through to compressible and incompressible gas gills (air bubbles) and tracheal gills (elaborations of the cuticle). During their development many insects transition from the aquatic to the terrestrial environment, so the respiratory adaptations associated with breathing water and air can be studied within a single species. The goal of my current NSERC research program is to investigate the respiratory and acid-base challenges associated with the water-to-air transitions displayed by dragonflies, damselflies, mayflies and stoneflies.
I am also interested in understanding why some insects breathe episodically while at rest, holding their breath for minutes to hours between brief bouts of gas exchange. These so-called discontinuous gas-exchange cycles appear to have evolved independently within at least 5 insect orders. However, the advantages associated with adopting this breathing pattern, and the neurological processes that underlie its production, remain the subject of lively debate. My previous research explored the gas-exchange strategies of terrestrial organisms, both animal and plant, that have secondarily invaded the freshwater aquatic environment. This included determining how sacred lotus use their leaves to pump pressurised air down to their roots growing in anoxic mud, and how bubbles of air carried by diving aquatic hemipterans (bugs) act as temporary ‘gas gills’ and buoyancy control devices.

My lab uses a wide range of research techniques, with an emphasis on in vivo measurements. To this end I use implantable fibre-optic sensors to measure oxygen levels directly within the insect tracheal system and pH levels within the insect’s haemolymph. These measurements are combined with flow-through respirometry systems to simultaneously record rates of oxygen consumption and carbon dioxide production. Video tracking and motion detectors record ventilatory movements and activity.