LONDON: Researchers have solved the mystery of one of nature’s oddest designs — the T-junction head of the hammerhead shark.

Until now, the best guesses have been that with eyes far apart on a bizarre brainbox called a cephalafoil, the hammerhead can either see more of the world around it and pinpoint prey more accurately; or that the head acts as a hydrodynamic foil to give the great beast extra lift.

But Stephen Kajiura of the Hawaii Institute of Marine Biology will add to the picture at an American Physiological Society meeting in San Diego. It does help the shark manoeuvre, but the hammer-shaped head is also a huge sensor, capable of detecting the electromagnetic fields of its prey.

There are several species of hammerhead: they average 3.5 metres in length, although the great hammerhead grows to about six metres. The females produce litters of 20 or 30 little sharks which grow up to feed on herring, squid, rays, crabs, sardines, swordfish, groupers, other sharks and, occasionally, humans. There have been hammerheads around for about 25 million years.

Sharks have natural electrodetectors on their heads to provide an extra sense. Dr Kajiura counted the number of electrosensory pores on ordinary sharks and hammerheads caught accidentally in nets, and found that the electroreceptors in young hammerheads were more numerous over a given area of skin. Since they had wider heads to start with, they should overall be better detectors.—Dawn/The Guardian News Service.