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Fast fish evolved similar design separately

Great white sharks and tuna separately evolved similar builds for speed, scientists said Wednesday.
A GREAT WHITE SHARK EXAMINES A DIVING CAGE OF THE SOUTHERN CAPE COAST
Sharks and tuna have been separated on the evolutionary tree for over 400 million years, but have similar muscles and tendons.Reuters
/ Source: Reuters

Great white sharks and tuna have a similar build for speed despite evolving separately for millions of years, scientists said Wednesday.

"Nature does it best in terms of design," said Jeanine Donley of the Scripps Institution of Oceanography in California. "It is amazing that they have developed to be so similar."

Lamnid sharks, which include mako and great whites, have been separated on the evolutionary tree from bony fishes, such as tuna, for over 400 million years. But the muscles and tendons that enable them to swim so fast are remarkably similar.

"Tunas and lamnid sharks have a body form that represents an extreme in biomechanical design for high-performance swimming," Donley said.

Lamnid sharks, which inhabit tropical to cold temperate waters in almost all seas, and tuna diverged from their ancestors in the design of their swimming features millions of years ago.

Their specialized features distinguish them from nearly all other fish and make them more like each other than their closest relatives.

The team, who reported their results in the science journal Nature, used video footage of sharks swimming in a tunnel and a device that measures muscle length during movement.

They believe it was evolutionary selection that allowed them to swim at high speed with a minimum of movement.

"There are body shapes ... the roundness, the degree of tapering, even the tail shape, that you can calculate what would be approximately the most efficient for steady, straight swimming or burst swimming," Donley said.

"These two types of fish have this particular type of body shape which is ideal for hydromechanical efficiency."

Commenting on the research, Adam Summers of the University of California, Irvine, said scientists have been speculating on the similarities between tuna and mako sharks for decades.

"Understanding the mechanisms behind their locomotion could lead to high-speed autonomous underwater vehicles," he added.