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Sharks & Rays Cool Facts: The Hammerhead

Why has the odd shape of the hammerhead´s head been so successful over the last 20 to 25 million years?

Sharks and rays form an amazing group of animals called elasmobranchs. Although there are lots of things yet to be discovered about this group, some particular features have drawn scientists’ attention, like the shape of the hammerhead shark. This shark owes its name to the weird shape of its head which has persisted for over the past 20-25 million years! Its presence in many hammerhead shark species with different head shapes tell of its evolutionary success.

There are a few hypotheses as to why this shape has been so successful and what advantages it gives to the shark. Some scientists think that this shape could be useful to trap its favorite prey, stingrays, by pinning them to the seafloor. Others think that the broader shape helps to find its prey because sharks and rays have hundreds of pores on their heads which are the open end of electrically sensitive organs known as ampullae of Lorenzini. Each ampulla, or vesicle, is filled with conductive gel and neurons project into the gel. The hammerhead shark has a much wider area on its head to have more of these sensory organs to better track odors and to detect the electric currents generated by potential prey more accurately. The shark’s eye placement, on each end of its very wide head, enhances binocular vision and allows it to scan more area more quickly than other sharks can. Scientists have found that hammerhead sharks could sense the electric field 50% farther away than could other sharks of the same size. It has also been suggested that it increases maneuvering capabilities.  When a hammerhead shark changes direction, it can tilt its big winglike head which is far forward of its center of gravity, and exert a huge turning force on the body. So, this shark can turn more quickly and make sharp turns more often than other species of sharks.

More information is needed to fully understand how this shape evolved and how it has persisted through time, although these are only some examples of the questions surrounding the hammerhead sharks. But whatever the reasons are for these particular body shapes, what it is for sure is how majestic these animals are when you are lucky enough to find them swimming around.  

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