Tuesday, February 1, 2011

Seahorse shape explained as stealth-attack adaptation

From Wired

According to a new explanation of seahorse shape, those distinctive S-curve bodies let them reach further than straight-bodied ancestors.

Compared to tube-shaped pipefish, their closest relatives, seahorses extend their snouts an extra 30 percent. The difference is only a few millimeters, but for animals with a strike range of a centimeter or two, it’s a big advantage.

“This makes them stealthier and sneakier hunters,” said
Lara Ferry, an Arizona State University ecomorphologist who co-authored the study, published Jan. 25 in Nature Communications. “Their prey is less likely to spot them coming, and they are less likely to miss a meal.”

To test the link between shape and hunting ability, Ferry’s team created a computer model predicting the movements of seahorses and pipefish.
By tweaking the features of the model fish, they could estimate how body curvature affected range.
They verified their results with high-speed video of seahorses and pipefish feeding.

The videos were needed, Ferry said, because the naked eye can’t see seahorses feed.
They’re among the fastest eaters known.

“From the time they spot prey and open their mouth, to the time the shrimp is completely devoured, is only four milliseconds,” said Ferry.

Seahorses rely on stealth attack because they’re poor swimmers.
While most fish, pipefish included, swim towards their prey, seahorses hide in sea grasses or corals, hang on with a prehensile tail, and wait for tiny shrimp to float by.
To prepare for a strike, they tense their muscles and — like a stretched sling-shot — snap forward.

Seahorses are also unusual for being monogamous, and are among the only species in which males bear young.

Links :
  • BBCNews : Seahorses' body shape explained

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