May 7, 2015
Eric Hopton for redOrbit.com – Your Universe Online
Not all fish species are completely cold-blooded. Some have a unique physiological characteristic – a web of arteries and veins that allows them to raise their internal temperatures higher than that of the water surrounding them. This gives them a big ecological advantage over their truly cold-blooded cousins as they can move up to twice as fast and twice the distance. One species, the white shark, has a migration range greater than that of the humpback whale.
An international team of scientists, including UC Santa Barbara research biologist Jenn Caselle, found that species with the ability to warm their core, a process called endothermy, can swim two and a half times faster and have much wider ranges. Some, including certain sharks and tuna species, can travel distances comparable to those of warm-blooded animals such as penguins and other marine mammals.
Transport costs on the rise
“The cost of moving faster and farther is high so there has to be an ecological reason that outweighs the physiological expenditure,” said Caselle. “These endothermic fishes are putting a lot more energy into each unit of movement than their cold-blooded counterparts are.
“In fact, the estimated cost of transport is twice as high, but in return they’re getting benefits from that increased swimming speed and wider range of migration,” she added. “We hypothesize these gains allow these endotherms to be more efficient hunters and to span larger areas in their migration, which probably provides feeding and reproduction benefits.”
The team beefed up existing data with new information by attaching sensors, designed and built by lead author Yuuki Watanabe of Japan’s National Institute of Polar Research, to several sharks in different locations around the world.
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