Smart elephant fish navigates in darkness with electric fields
Written by Dr. H. P. Bustami
Thursday, 23 August 2007
|The african elephant fish or blue jawed elephantnose (Gnathonemus tamandua) is able to navigate in total darkness, finding food, seeing and analysing different objects and hindrances in size and structure. In their recent publication in "Journal of Experimental Biology" zoologists from the university in Bonn, Germany, now reported several interesting and new findings about how sophisticated the animals behaviour is:
An Einstein among electrical fish, elephant fish from africa. Prof. Dr. Gerhard von der Emde with a model (Courtesy of G. von der Emde, University of Bonn, Germany)
In the nose of the fish are more than 500 specialised electrical sensor cells located which are able to detect smallest changes of the electrical field which is surrounding the blue jawed elephantnose. The field is caused by muscle cells in the fishs tail which give small pulses with 80 Hz. The sensors in its nose can detect for example the electrical fields which are caused by potential prey like aquatic insect larvae which hide under the surface on the ground of a river or pond. Slowly swimming over the ground these smart fishes are turning left and right their nose with the sensor cells in it, working thus like gold miners using a metal detector. This way of navigation is called electrolocation.
The scientists in the research group of Gerhard von der Emde offered in total darkness (under infrared light which is invisible for the fish but not for the scientists by using special cameras) two different shapes - a quadrat and a pyramid - to the fish. When it swam to the pyramid it found food (moskito larvae) and swimming to the quadrat no reward was available. Quickly the animal learnt to distinguish the form of both shapes and turned in 9 of 10 cases towards the pyramid where it found food. Also volumes of objects and the structure of materials (dead or alive animals, prey) can obviously be measured by the fishs ecolocation system.
"These fish are rather smart and have a huge brain in relation to their body size" explains Prof. Dr. Emde; when he tried to conduct similar complicated behavioural experiments with electrical from South America it failed. So Gnathonemus tamandua seems to be the Einstein among electrical fishes.
- Gerhard von der Emde and Steffen Fetz; Distance, shape and more: recognition of object features during active electrolocation in a weakly electric fish, J. Exp. Biol 2007 210: 3082-3095.
more about elephant fish: http://en.wikipedia.org/wiki/Mormyridae
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