T as electromagnetic

Animals / What is the meaning of the unique head structure of the haptischen

By Tim Redford

Photo: Todd Kennedy Petition. The head is a huge sensor

Researchers have solved the mystery of one of the strangest designs in nature - the head of the heptacean, which is shaped like the letter T.

Until now, one of the accepted explanations for the special head shape was that thanks to eyes located at a great distance from each other on an expanded brain box, the shark could see a larger segment of the world around it, and focus on the prey with greater precision. According to another theory, the head serves as a kind of hydrodynamic lever that helps the giant animal to maneuver through the water more efficiently.

But Stephen Kajiura of the Hawaii Institute of Marine Biology added new information to the picture yesterday. In a lecture he gave at the conference of the American Physiological Society in San Diego, Kajiura claimed that the head does indeed help the shark to maneuver in the water, but it is also a huge sensor capable of locating the electromagnetic fields of its prey.

There are several species of the haftich: their average length is 3.5 meters, although the damaged haftich reaches up to six meters. The females spawn about 20 to 30 small sharks that feed on squid, barnacles, crabs, sardines, swordfish, buritans, other sharks and sometimes humans. Hammerheads have existed on Earth for 25 million years.

Sharks have natural electromagnetic sensors on their heads that act as an extra sense. Caggiora counted the electromagnetic pores known as "Ampoules of Lorenzini" in normal sharks and in hammerheads accidentally caught in nets. He found that juvenile hammerheads had more sensors than sand sharks on a given skin area. Because hammerheads have wider heads to begin with, Kajiura assumed their detection abilities were better.

He photographed the sharks as they swam: hammerheads maneuvered better than sandbar sharks, making sharper turns at higher speeds. But the real test was when Kajiura turned on electric lures in the shark enclosure and followed their movements in slow motion.

The hammerheads bit the lures every time. In contrast, the sand sharks sometimes missed the electrical signal even when it was ten centimeters away from them. The T-shape didn't give the hammerfish greater sensitivity, Caggiora concluded, but instead allowed their sensors to cover a wider search area. In this way, the chances of the sharks to encounter prey and grab it in their jaws are improved.

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