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Nearly one-fourth of the 36 seahorse species assessed by the International Union for Conservation of Nature are threatened with extinction. Illustrates SEAHORSES (category a) by Juliet Eilperin (c) 2012, The Washington Post. Moved Monday April 16, 2012. (MUST CREDIT: Michelle Fisher/Mote Marine Laboratory). ORG XMIT: MIN2013120622104831

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Briefs: Seahorses have a head for hunting

  • December 7, 2013 - 3:46 PM

Seahorses have a head for hunting

One of the most effective predators in the animal kingdom is smaller than your thumb, and it won’t win any races. The dwarf seahorse is less than an inch long, and with its S-shaped body and small dorsal fin, it’s going nowhere fast. But oddly enough, this unusual body shape and lack of speed make the seahorse a menacing hunter.

Unlike fish with protruding jaws, the seahorse has a long, thin snout that it rotates toward prey in a swift snatching motion called pivot feeding. This millisecond maneuver creates suction that pulls in the seahorse’s prey, but it works only at extremely close range.

“We knew that these sea horses were feeding successfully by doing this short-range swinging motion,” says Brad Gemmell of the University of Texas at Austin’s Marine Science Institute. “But they must first overwhelm the ability of the prey to escape. Our question was: How do they get so close without alerting their prey?”

This is no mean feat. Copepods, the tiny crustaceans that dwarf seahorses eat, are highly sensitive to changes in the water around them. They rely on small sensitive hairs to detect motion, and once they sense danger they have one of the fastest escape responses of any organism on the planet: They are able to flee at 500 body lengths per second. By comparison, a cheetah can manage only 30 body lengths per second.

Gemmell and a team of researchers used high-speed cameras to measure the movements of seahorses. They found that the water just above the snout of the seahorse was significantly less turbulent than above or to the side of its body. As a sea horse orients itself toward its prey, the calmer water directly above its mouth allows it to sneak up and pounce.

The “no-wake zone” allowed the sneaky seahorses to catch their intended prey an impressive 90 percent of the time, said the authors of the study, which was published in Nature Communications.

 

faulty Brain tie may be behind dyslexia

A faulty connection between where the brain stores the auditory building blocks of language and where it processes them may be to blame for dyslexia, a new study suggests.

The findings represent the first neuroanatomical evidence that the spelling and reading disorder striking people who otherwise can speak a language fluently lies in a connectivity problem in the brain’s white matter, where nerve fibers relay electrochemical signals. Various degrees of dyslexia strike about one in 10 people, making it difficult for them to analyze and assemble letter combinations and relate them to the auditory packets of learned language, called phonemes.

A Belgium-based research team used functional magnetic resonance imaging machines to scan the brains of 45 college-age adults (23 with dyslexia, 22 without) while they distinguished among a variety of sounds, some of which differed in subtle ways, then built a sophisticated correlational map.

Both groups were able to distinguish and sort those sounds accurately, though the dyslexic group did so more slowly, said the study published online in the journal Science. But the white matter tracts connecting the phoneme area to a part of the brain that contains the Broca’s area, which regulates the conversion of language to speech, was weaker for the dyslexics as a group, the study found.

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