Seahorses are notoriously slow and awkward. But as scientists have just learned, their unique shape allows them to overcome these limitations. Despite their cute and unassuming appearance, seahorses are actually proficient killers.
Seahorses are slow. Like, ridiculously slow. In fact, the researchers who conducted the study say they're slowest swimming fish known to science. But they can capture prey that swim at incredible speeds — and at an incredibly proficient rate; in ideal conditions, seahorses catch their intended prey 90% of the time, a success rate that would be amazing for any predator.
So how's this possible? New research shows it all has to do with the unique shape of the seahorse's head and a technique known as "pivot" feeding — a strategy requiring a sudden, rapid movement at extremely close range. But getting close to prey is not easy underwater, as many of these tasty creatures have evolved to become hydrodynamically sensitive. An approaching animal can often trigger an escape response. Seahorse prey, namely copepods, can detect waves from incoming predators and then jolt away at speeds of more than 500 body lengths per second. That's like a human swimming at 2,000 mph (3,218 km/h)!
So, for pivot feeding to work, seahorses have evolved a rather unique morphology. Its head creates what the scientists call a reduced fluid deformation zone, or "no wake zone." Essentially, its a perfectly crafted shape, particularly above the end of the snout, that minimizes the degree to which water is disturbed by an object moving through it. This allows seahorses to approach highly sensitive copepod prey undetected. And then, using a quick and deadly strike, it's game over.
To reach this conclusion, a research team from the University of Texas at Austin used a special technique to capture the movement of water around the seahorses in 3D. The technique, called holographic and particle image velocimetry (PIV), utilizes a microscope fitted with a laser and a high-speed digital camera.
Read the entire study at Nature Communications: "Morphology of seahorse head hydrodynamically aids in capture of evasive prey".