In the murky waters of their African home, mormyrid electric fish(Brienomyrus brachyistius) use pulses from their electric organ to sense their surroundings, find prey and communicate with each other. The waveform of a fish's pulse is like an electronic `fingerprint', telling others their species, sex and social status. On the other hand the sequence and pattern of pulses tells other fish a great deal about an animal's behaviour and its motivation, for example if it is aggressively defending its territory or courting another fish.
Researchers hit a problem when they wanted to find out more about the fishes' courtship signals, because electric fish are fiendishly difficult to breed in captivity. However Ryan Wong and Carl Hopkins tempted four pairs of fish to court each other by carefully creating ideal breeding conditions in the lab (p. 2244). Using a combination of video recording and computer software that distinguished between the electric organ pulses from individual fish, the team classified nine behaviours and 11 pulse sequences that occurred during both normal interactions and courtship. For example during courtship, males typically lunge at females, follow them around the tank and circle head to tail with them before spawning. Certain pulse sequences were more common during courtship, where male fish serenade females with lower frequency`creaks' and higher frequency `rasps'. The team also found that males and females took part in duets, alternating sequences of rasps and staccato`bursts'. The next step will be to decode the fishes' transmissions and unravel their meaning.