African Fish Family with Shocking Communication Skills

An African family of fish has a unique recognition tool—an electrical signal that is distinctive not only to species, but also to sex, dominance, and even to individual identity. A new study found that that jump in communication skills led to a species explosion for the weakly electric group, the Mormyridae, or mormyrids. Three anatomical advances underlie the ability to send and receive diverse electrical signals: cells able to produce different discharges, a global distribution of the sensors that detect the discharges’ shape, and a more complex signal-processing area of the brain to analyze them. There is an electric organ located at the base of a fish’s tail that consists of stacks of disk-like cells called electrocytes, which all fire action potentials simultaneously, and so their tiny action potentials sum to produce a discharge that is typically about a few volts. These signals don’t propagate as electromagnetic waves. Instead they exist as an electrostatic field, just like you’d get by sticking a battery in the water. Weakly electric fish have several types of electroreceptors but the ones important for communication are called knollenorgans or tuber, because they consist of bulbous cells buried just under the fish’s skin. They respond to a voltage rise, firing a time-locked spike in response to outside positive-going voltage changes. Watch the video.Learn more from Laboratory Equipment.