Fish from the lower reaches of the Congo River, of the genus Campylomormyrus, use the discharge of their electric organ to find prey. Such discharges may also be driving species divergence, suggest experiments by Philine Feulner, now of the University of Sheffield, UK, and her colleagues.
They gave ready-to-spawn C. compressirostris females a choice between males of the same species, and either a closely related but electrically different C. rhynchophorus, or a distantly related but electrically similar C. tamandua. The procedure was repeated with a simulation of the males' electrical discharges in place of the male fishes.
The electric signal seems to be all-important. In both tests, females preferred their own kind over C. rhynchophorus, but not over C. tamandua.