African fish, sex, and electricity

This video from the USA says about itself: Elephantnose Fish at San Antonio Zoo.

From New Scientist:

Electric fish prefers sexual charge of its own species

26 November 2008 by Ewen Callaway

People often compare sexual attraction to a jolt of electricity, but in some animals a charged atmosphere is very literal.

Male elephant nose fish are known to lure females with the help of an electric field. Now lab experiments suggest that females fancy the electric aura of males of their own kind over the spark of closely related species.

Such electric attraction could maintain genetic differences between the nearly identical fish species, says Philine Feulner, a behavioural ecologist at the University of Sheffield, UK, who led the study.

Classified as weakly electric fish because they can’t muster more than 1 volt – electric eels deliver 500-volt zaps – elephant nose fish generate an electric current with an organ in their tail made from specialised muscle cells.

Irresistible charge

The field produced helps the long-nosed nocturnal fish to find food and navigate the murky waters of the lower Congo River, Feulner says.

Among several closely related species all living in the same vicinity, the jolts differ enough in their length, size, and frequency, that Feulner and her colleagues could measure the difference with an electrode inside the fish’s aquarium. They could even mimic electric pulses of different species using a simple set-up.

When dropped between two species of males, ready-to-spawn Campylomormyrus compressirostris females spend most of their time near males of their own kind. A barrier kept the females from acting on their desires, but that didn’t stop fish from releasing eggs after the experiment was complete.

Feulner’s team repeated the experiment with artificial electric fields in place of actual male fish. Again, females lingered near to the same-species signal.

Species signature

The two species of elephant nose fish from the family Mormyridae might still interbreed to produce offspring, but their differing electric fields might keep interspecies sex to a minimum, Feulner speculates. This might occur if differences in the strength and duration of electric discharges determine what and where the fish can eat.

Britain: Eels in crisis after 95% decline in last 25 years: here.

African papyrus swamp fish: here.