Navigation Links
Wide heads give hammerheads exceptional stereo view
Date:11/26/2009

Hammerhead sharks are some of the Ocean's most distinctive residents. 'Everyone wants to understand why they have this strange head shape,' says Michelle McComb from Florida Atlantic University. One possible reason is the shark's vision. 'Perhaps their visual field has been enhanced by their weird head shape,' says McComb, giving the sharks excellent stereovision and depth perception. However, according to McComb, there were two schools of thought on this theory. In 1942, G. Walls speculated that the sharks couldn't possibly have binocular vision because their eyes were stuck out on the sides of their heads. However, in 1984, Leonard Campagno suggested that the sharks would have excellent depth perception because their eyes are so widely separated. 'In fact one of the things they say on TV shows is that hammerheads have better vision than other sharks,' says McComb, 'but no one had ever tested this'. Teaming up with Stephen Kajiura and Timothy Tricas, the trio decided to find out how wide a hammerhead's field of view is and whether they could have binocular vision and publish their results on November 27 2009 in the Journal of Experimental Biology at http://jeb.biologists.org.

Hammerheads come in all shapes and sizes so McComb and Kajiura, opted to work with species with heads ranging from the narrowest to the widest. Fishing for juvenile scalloped hammerheads off Hawaii and bonnethead sharks in the waters around Florida, the team successfully landed the fish and quickly transported them back to local labs to test the fish's eyesight.

The team tested the field of view in each shark's eyes by sweeping a weak light in horizontal and vertical arcs around each eye and recorded the eye's electrical activity. Comparing the hammerheads with pointy nosed species, the team found that the scalloped hammerheads had the largest monocular visual field, at an amazing 182 deg., and the bonnethead had a 176 deg. visual field, which was bigger than that of the pointy nosed blacknose and lemon sharks, at 172 deg. and 159 deg., respectively.

Having collected the animals' monocular visual fields, the team plotted the visual fields of both eyes on a chart of each fish's head to see whether they overlapped. Amazingly, they did. The scalloped hammerhead had a massive binocular overlap of 32 deg. in front of their heads (three times the overlap in the pointy nosed species) while the bonnet head had a respectable 13 deg. overlap. And when the team measured the binocular overlap of the shark with the widest hammerhead, the winghead shark, it was a colossal 48 deg. The hammerheads' wide heads certainly improved their binocular vision and depth perception.

Finally, the team factored in the sharks' eye and head movements and found that the forward binocular overlaps rocketed to an impressive 69 deg. for the scalloped hammerheads and 52 deg. for the bonnetheads. Even more surprisingly, the team realised that the bonnethead and scalloped hammerheads have an excellent stereo rear-view: they have a full 360 deg. view of the world.

'When we first started the project we didn't think that the hammerhead would have binocular vision at all. We thought no way; we were out there to dispel the myth,' says McComb. But despite their preconceptions, the team have shown that the sharks not only have outstanding forward stereovision and depth perception, but a respectable stereo rear view too, which is even better than the TV shows would have us believe.


'/>"/>

Contact: Kathryn Knight
kathryn@biologists.com
44-122-342-5525
The Company of Biologists
Source:Eurekalert

Related biology news :

1. Utah ethicist heads stem cell panel
2. Venomous sea snakes play heads or tails with their predators
3. Dogs, humans, put heads together to find cure for brain cancer
4. Our brains make their own marijuana: Were all pot heads deep inside
5. Male crickets with bigger heads are better fighters, study reveals, echoing ancient Chinese text
6. CT scans reveal that dinosaurs were airheads
7. United we stand: When cooperation butts heads with competition
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/10/2016)... March 10, 2016   Unisys Corporation (NYSE: ... Protection (CBP) is testing its biometric identity solution at ... to help identify certain non-U.S. citizens leaving the ... test, designed to help determine the efficiency and accuracy of ... February and will run until May 2016. --> ...
(Date:3/8/2016)... 2016   Valencell , the leading innovator ... has secured $11M in Series D financing. The ... venture fund being launched by UAE-based financial services ... investors TDF Ventures and WSJ Joshua Fund. Valencell ... triple-digit growth and accelerate its pioneering innovation in ...
(Date:3/2/2016)... March 2, 2016 ... addition of the  "Global Biometrics Market in ... ,     (Logo: http://photos.prnewswire.com/prnh/20130307/600769) , , Global biometrics ... at a CAGR of around 27%   ... has announced the addition of the  "Global ...
Breaking Biology News(10 mins):
(Date:4/27/2016)... ... ... Pittcon Organizing Committee is pleased to announce that Charles “Chuck” Gardner was named president ... Since then, he has served in a number of key leadership positions including secretary ... and exposition committees. In his professional career, Dr. Gardner is the director of product ...
(Date:4/27/2016)... and RESEARCH TRIANGLE PARK, N.C. , ... UTHR ) announced today that Martine Rothblatt ... Therapeutics will provide an overview and update on the ... Annual Health Care Conference. The presentation will ... a.m. Eastern Time, and can be accessed via a ...
(Date:4/27/2016)... ... April 27, 2016 , ... PathSensors, Inc., a ... Board. Dr. Lamka will assist PathSensors in expanding the use of the company’s ... the CANARY® test platform for the detection of harmful pathogens, including a number ...
(Date:4/27/2016)... ... April 27, 2016 , ... Global Stem Cells Group and ... Symposium as other research and development initiatives for potential stem cell protocol management for ... Stem Cells Group executives began meeting to establish a working agenda and foster initiatives ...
Breaking Biology Technology: