Why do elephantnoses produce electricity?

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Elephant nose mormyrids produce little zaps of electricity, but why do they do this and what allows them to produce electricity in the first place?

Elephant noses, or mormyrids, are weakly electric, so while electric eels produce a powerful 500 volt zap to stun prey, mormyrids produce less than a volt and use it for communication in the murky waters in which they live. 

The zap, known as an electric organ discharge or EOD,  comes from a special muscular organ in their tail and the length, frequency and size is specific to the species producing it. 

The fish can detect the EODs of other mormyrids allowing them to locate members of the same species to spawn with, and allows them to prevent hybridising with other species even when they can’t see who they’re spawning with.

Recent research on populations of the elephant-nosed species Campylomormyrus numenius has found that different fish produce slightly different EODs. 

These were once considered to be age-related differences, as the fish varied little in their appearance, however, DNA studies have shown that the fish actually differ genetically. 

This suggests that C. numenius contains so-called cryptic species that are as yet undescribed, which means more species will be named later.

This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.