Quick Dips

The Fishy Fast Lane

It's fish on the table at Massey University, but the physiologists are studying it rather than eating it. Dr Peter Davie and his colleagues are examining a wide range of fishes to learn more about how the heart and coronary circulation system function. The fishes range from sedate flounders to speedy tuna.

"Tuna are fishes who live in the metabolic and physiological fast lane, " says Davie. "If anything needs a coronary unit, tuna does."

Some fishes have coronary circulations which support high blood pressure and high levels of activity. Others have a more primitive system and consequently take things slowly. The tuna's heart, for example, beats 110 times a minute, the trout's only 50. Fish thus represent an evolutionary spectrum in terms of development of the circulatory system.

The coronary control systems that the active fish have are similar to those of mammals, involving nerves, receptors and hormones as well as a variety of arterial mechanisms. These ensure that high blood pressure is maintained, the heart can beat faster and faster swimming speeds are possible. A better understanding of how fish hearts function may ultimately provide greater understanding of the human circulatory system.