Australasian Science: Australia's authority on science since 1938

Parasites a Drag for Fish

By Stephen Luntz

A parasite affects fish health more through the loss of its streamlined shape than through the blood it sucks, two PhD students at the Australian National University have found.

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While it is not clear how widely applicable their results are to other parasites, they may have profound implications for the methodology of marine biologists.

Sandra Binning and Dominique Roche put bridled monocle bream, a coral reef fish, into a tank where water flows past at an adjustable rate, forming the equivalent of a treadmill for fish. The tank also allowed them to measure oxygen consumption.

“Oxygen consumption is a proxy for energy consumption: if a fish consumes more oxygen it is burning more fuel and will need to eat more,” says Binning. “Eating more means you may be more exposed to predation and have less time for other important activities, such as attracting mates.”

Unsurprisingly, infection with the crustacean Anilocra nemipteri increased the bream’s oxygen requirements. However, the difference was small at low speeds. When the parasite was removed their oxygen consumption returned to normal within 24 hours. “This is too fast for physiological effects such as anaemia,” Roche notes.

When the students glued a plastic model of the parasite to the fish’s head, the fish required the same additional oxygen as when they were infected by a real parasite. The finding has been published in Biology Letters.

“It’s similar to drag on a car with a roof rack. At slower speeds you don’t consume more petrol. But at higher speeds, the...

The full text of this article can be purchased from Informit.