New Information on the Hammerhead Shark Published

Study published in a current problem of the Journal of Experimental Biology might have solved the enigma of why hammerhead sharks have such odd-shaped heads.

One theory suggests that the broadly set eyes provide the sharks better binocular vision, scientific opinion that have been sharply divided by an issue for years.

Michelle McComb, Timothy Tricas and Stephen Kajiura examined this theory by evaluating the visual areas of three hammerhead species: the bonnethead shark, (Sphyrna tiburo), scalloped hammerhead shark (Sphyrna lewini) and the winghead shark (Eusphyra blochii), with that of two ordinary shark species: the orange shark (Negaprion brevirostris) and the blacknose shark (Carcharhinus acronotus).

Copyright © Barry Peters, Creative Commons

The writers put devices on the shark’s skin to measure its mind exercise when beams of sunshine were shone from various places around the tank; they additionally measured eye turn and mind yaw to ascertain if the sharks pay for big blind places before the top.

The results suggest that the area of binocular vision was around four occasions greater in hammerhead sharks than in ordinary sharks: the anterior binocular overlap of the orange and blacknose sharks were 10 and 11 degrees respectively, while those of the bonnethead, scalloped hammerhead and winghead sharks were 13, 34 and 48 degrees respectively.

These outcomes suggest that the higher the sideways growth of the mind, the bigger the binocular field of vision (bonnethead sharks have the lowest sideways expansion of the mind and winghead sharks the greatest).

For more details, see the newspaper: McComb, DM, TC Tricas and SM Kajiura (2009) Increased visual areas in hammerhead sharks. Journal of Experimental Biology 212, pp.
4010–4018.