January 26, 2011

Why Are Seahorses Shaped Like That?

Scientists say that they now understand why the seahorse evolved its equine-like head and S-shape.

BBC reports that a new study has shown that seahorses are able to strike at more distant prey, compared to straight-bodied pipefish, from which they evolved.

The research team found that seahorses' delicate curves evolved to help it hunt and feed.

Both seahorse and pipefish feed on tiny marine creatures, striking at them and sucking them into their snouts.

However, seahorses sit and wait for their little victims to pass by, unlike most pipefish.

Sam Van Wassenbergh from the University of Antwerp in Belgium showed by using high-speed footage and mathematical models that the curve in a seahorse's "neck" allows it to strike at more distant prey.

"They rotate their heads upward to bring their mouth close to the prey [passing above]," Wassenbergh told BBC News.

Seahorses' curved bodies mean that when they do this, their mouths also moved forward, helping to bring passing small crustaceans within sucking distance of their snouts.

"My theory is that you have this ancestral pipefish-like fish and they evolved a more cryptic lifestyle," Wassenbergh told BBC.

He said this shift in behavior to become a more "sit and wait feeder" meant that they needed to capture prey that was further away.

So these new fish then became S-shaped seahorses, which could use their bodies to strike out.

"They grasp with their tail, to attach to seagrass and wait for food to pass by within striking distance," he says.

The study was published in the journal Nature Communications.


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