People

My research activities fall into two broad categories: one, the comparative physiology of diving animals and two, the functional morphology of circulatory systems in a range of vertebrates and invertebrates. From the start of my research career I brought both a behavioral and mechanistic approach to my studies on the control of heart rate and blood flow in diving animals and the impact of blood flow changes on cellular metabolism during submergence.. On the mechanistic level, most recognition has accrued for identifying the sensory receptors that cause the cardiovascular adjustments in forced and voluntary dives. For instance, with Michael Purves, I was the first to identify and define the essential role of chemoreceptors (which monitor blood oxygen levels) in forced diving responses of ducks. This is now cited as a “truth”, usually without attribution. Also, my study on blood pressure receptors was the first physiological demonstration, which I substantiated with morphological studies, of the existence of baroreceptors in non-mammalian vertebrates. In 1984, I was elected to fellowship in the Royal Society of Canada in recognition of my research on blood pressure receptors. In 1986, I gave a plenary lecture on my diving studies to the International Union of Physiological Sciences.

On the behavioral side, my colleagues and I made the fist studies of cardio-respiratory performance from free swimming salmonids and tuna and free flying birds in a wind tunnel. The salmonid exercise paper is one of the most cited papers in the fish literature. For DFO I did a study on the swimming performance of fishes from Mackenzie river which was published as a technical Bulletin (1974). Interestingly, I have concentrated recently on disproving the supposed causative relation between exercise and heart rate variability in free diving animals. With my students and collaborators, I pioneered the use of data logging devices to monitor dive depths and times, swimming velocity, heart rate, body temperature and feeding in free-ranging elephant seals and leatherback turtles. For the research on elephant seals and leatherback turtles I was honored in 2000 by the award of the Flavelle Medal of the Royal Society, for outstanding contributions to biological science in the last 10 years.

The second area of my research is concerned with the circulatory structure and function in a range of vertebrates and invertebrates. Studies have ranged from looking at the role of extra-cardiac chambers, in addition to the ventricle, in propelling blood around the circulation in fishes and frogs to the roles of the multiple hearts of invertebrates. A prolonged interest in the bulbus arteriosus, an elastic chamber between the ventricle and the aorta in teleost fish has resulted in two papers that the referees described as the “definitive” study. My research has also looked at the way active valves function in the vertebrate heart, which led to seminal studies on cardiac dynamics of crocodilians. Crocodilians have a completely divided ventricle, unlike all other reptiles, but venous blood can still be re-circulated to the body, by-passing the lungs. I have reviewed crocodilian cardiac dynamics in the Fry Medal lecture to the Canadian Society of Zoologists (1992) and plenary lectures to the International Union of Biologists in Birmingham, U.K. (1995), the German Zoological Society in Oldenburg (1996) and as a symposium contribution to the International Union of Physiological Sciences in St. Petersburg, Russia (1997). In March 2001, I was invited to present my crocodilian research as the Lubinsky lecturer at the University of Manitoba.