Shark Electric Sense
Ampullae of Lorenzini Electroreceptors Detect Electromagnetic Fields
Aug 2, 2008
In addition to the familiar senses of smell, touch, tasting, hearing and sight sharks can detect vibration and electric signals.
Sharks' Sensitive Sense of Smell
Some species of shark can detect one part per million of blood in seawater, and many are attracted to the smell of sewage outfalls. A few species of shark will occasionally poke their heads out of the water (spy-hop) and look around. It is thought that this might be more to do with ‘smelling around’ since smells carry better in air then in water.
Touch and Taste
Sharks often grab things in their mouth to investigate them. They frequently bite buoys, and maybe the occasional swimmer who gets grabbed is more an object of curiosity than an intended meal. This might also go some way to explain ‘attacks’ on boats – a curious electromagnetic field requires further investigation.
Sight
Shark eyes are especially effective in dark conditions because they have an extra layer of tissue behind the retina which reflects the light. In all other ways the shark’s eye is similar to that of other vertebrates. Some species have an extra membrane covering the eye which protects the eye without loss of vision.
Hearing and Lateral Line Sense
Sharks probably hear very well, and this sense is merged with their lateral line sense. All fish have this additional sense, which detects vibrations. It allows sharks to home in on unusual struggling in the water.
Electroreception
The ‘Ampullae of Lorenzini’ in the head of a shark can detect the very weak electromagnetic fields given off by all living things. They can also pick up the signals given off by rusting metal, and of boats as they move through the earth’s electromagnetic field. It has been suggested that this might explain why sharks sometimes attack boats – they are just a bit confused! Detecting the earth’s magnetic field itself might also help sharks to navigate.
Recent research, using tags and satellite surveillance has shown that some sharks (Basking Sharks) are capable of long distance migrations – from Britain to Canada in one individual. Some Great Whites regularly move from California to Hawaii and back, but it is not clear why they do this.
Brain
The shark brain is roughly the same size (considering body mass) as in other vertebrates, and some species are quite good at problem solving. As would be expected the hunters appear to be the most intelligent, sometimes even appearing to ‘play’ with objects such as seaweed. They can also learn, and Great Whites are reputed to be scared of schools of dolphins.
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