Hammer Time

Every time you see me that Hammer’s just so hype
I’m dope on the floor and I’m magic on the mic
Now why would I ever stop doing this
With others makin’ records that just don’t hit

I toured around the world from London to the Bay
It’s Hammer Go, Hammer MC Hammer, Yo Hammer
And the rest can go and play

This post was chosen as an Editor's Selection for ResearchBlogging.org

There are two kinds of people.  Those who admit they love and know the lyrics to You Can’t Touch This and those who won’t admit they do.  There are also two kinds of sharks.  Those that bring the hammer and those that don’t.

Hammerhead sharks possess an amazing horizontally expanded head, reaching widths of 50% in some species, referred to as cephalofoils (from the Latin cephalicus meaning head and foil from hydrofoil) However, the evolutionary processes that drove the amazing head shapes of hammerheads remained a puzzle.

The cephalofoil is thought to confer multiple advantages for the skark, turning sharks into supersharks. Researchers speculate that it could potentially provide greater swimming ability and maneuverability, enhanced ability to capture and eat prey, heightened electrosense, and superior olfactory abilities. As if sharp teeth and speed were not enough?

Photo from Wikimedia Commons and available through the Creative Commons Attribution 2.0 License.

Photo from Wikimedia Commons and available through the Creative Commons Attribution 2.0 License.

New work by McComb and colleagues examines another hypothesis—enhanced sight. Increasing distance between the eyes may increase stereovision and depth perception. The team compared sharks with varying size cephalofoils, from hammerheads with a head shaped like a shovel to those with a prominent T-shape. By passing a weak light over each eye and recording the eye’s electrical activity, McComb and authors were able to measure the field of view for each shark.

Hammerhead possessed the largest visual fields from 176-182 degrees compared to pointy nosed sharks at 159-172 degrees. The team also found that scallop hammerheads possessed tremendous binocular overlap at 32 degrees with the widest hammerhead, the winghead shark, 48 degrees, nearly three times the overlap of common sharks. The cephalofoil also benefits hammerheads in one other way—rear vision. Common sharks can only look forward compared to the full 360 degree view of a hammerhead. Hammerheads also compensated for blind areas by moving the head back and forth left to right, i.e. yawing, which increased with the size of the cephalofoil. This provides the hammerheads with a greater viewable space and more spatial information.

School of scalloped hammerheads (Sphyrna lewini) in the Galapagos. Source Anthony Patterson available from Wikimedia commons and available Creative Commons Attribution 2.0 License.

School of scalloped hammerheads (Sphyrna lewini) in the Galapagos. Source: Anthony Patterson. Available from Wikimedia Commons and available Creative Commons Attribution 2.0 License.

Thus the Hammer is just so hype because of increased sight…not dopeness on the dancefloor or the mic.

Variation in cephalofoils in hammerhead sharks

Variation in cephalofoils in hammerhead sharks. Figure from McComb et al. 2009

McComb, D., Tricas, T., & Kajiura, S. (2009). Enhanced visual fields in hammerhead sharks Journal of Experimental Biology, 212 (24), 4010-4018 DOI: 10.1242/jeb.032615

Dr. M (1618 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, created to facilitate research to address fundamental questions in evolutionary science. He has conducted deep-sea research for 11 years and published over 40 papers in the area. He has participated in dozens of expeditions taking him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses mainly on marine systems and particularly the biology of body size, biodiversity, and energy flow. He focuses often on deep-sea systems as a natural test of the consequences of energy limitation on biological systems. He is the author and chief editor of Deep-Sea News, a popular deep-sea themed blog, rated the number one ocean blog on the web and winner of numerous awards. Craig’s popular writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.





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5 comments on “Hammer Time
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  2. That is really neat! But I don’t understand how the field-of-view test results also ruled out the other supposed benefits of the cephalofoil that you mentioned: “greater swimming ability and maneuverability, enhanced ability to capture and eat prey, heightened electrosense, and superior olfactory abilities…”?

  3. @DeLene
    They don’t necessarily rule the other factors out. However, this is the only one of the hypotheses that is tested and/or positively supported.

  4. Pingback: ResearchBlogging.org News » Blog Archive » Editor’s Selections: Speciation, Sharks, and Invasions

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