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Electroreception in Hammerhead Sharks
All living marine organisms generate an electric field around their body and all elasmobranchs possess a sensory system, the Ampullae of Lorenzini (AoL), which enables them to detect these weak electric fields and use them to orient to cryptic prey.
Although current research examines only prey-simulating electric fields, the experimental protocol could be expanded to test a variety of attractive and adversive stimuli. Funding for the research described above was provided in part by the Raney Fund for Ichthyological Research.
Quicktime Movie
(3.7 MB) of a juvenile hammerhead biting an electrode (~25 sec) This site was
created by Timothy Fitzgerald and is maintained by
Nick
Whitney |
The electroreception
research at HIMB focuses on detection of these prey-simulating electric fields in a
semi-natural habitat. A 1m x 1m clear acrylic plate is placed on the bottom of the
shark pond and one of four electric dipoles is activated with a weak electric
current. The sharks orient to the electric field and bite it as if it were a natural
prey item. The response behavior is videotaped from the surface and analyzed frame
by frame to quantify orientation distance and angle which are then used to calculate the
strength of the electric field at the point where the shark initiated its attack.
Positive feeding
responses have been elicited from several shark species, but most of the research at HIMB
is conducted with juvenile scalloped hammerhead sharks (Sphyrna lewini). Hammerhead
sharks have a unique head morphology which as not arisen in any other fish. This
unusual head shape may confer a sensory advantage by spacing AoL pores over a wider area
and also making the lengths of the AoL canals longer than in a carcharhiniform
shark. By comparing the response of hammerhead and carcharhinid sharks it may be
possible to determine if the hammerheads are indeed more sensitive to weak electric
fields.