Thanks to collective sense, electric fish can perceive better

Two see more than one. This also applies to elephant fish from African rivers. To “see” in muddy water, these fish use a special sense that humans do not have. It emits electrical impulses that you also receive. This allows them to detect prey with great accuracy, comparable to the sonar pulses of bats and dolphins.

But these fish also use the signal from other fish of their kind and thus get a better picture of the prey. Such “group sense” has never been demonstrated before in the animal world. American researchers describe it This week in the scientific journal nature.

elephant fish (Gnatonimus Pietersi), also known as tapirs, are named because they have strange trunks. They use it to search for food in the mud of the river bottom. They don't do this just by touch. The skin of these trunks contains many electroreceptors: nerve endings that can sense electrical fields. They produce these electric fields themselves using an organ at the base of their tail. This organ contains electrical cells: special cells linked to muscle cells, which can generate small currents.

Objects in an electric field, such as prey, distort the field depending on how well they conduct electricity. Fish feel this deformation through their electrical sensors, which are located mainly on their trunks, but also on the rest of the body. This deformity casts a shadow on the fish's body. The brain interprets the size, shape, and intensity of this shadow, and then knows exactly what is on the horizon and where.

Bats and dolphins

The American researchers were curious about what fish actually do with the signals they receive from other species. The literature has already looked at how to ensure that electro-sensitive fish, as well as bats and dolphins using their sonar, are not confused by each other's signals. For example, by not sending their pulses at the same time, but alternately. But whether they actually benefit from others' signals has never been investigated.

The Americans first made a computer model in which they modeled these electric fields for groups of fish. This showed that the collective “image” of each fish is stronger and clearer than the signal one fish receives from itself alone. Not surprisingly, the researchers write: Engineers have long known, for example from sonar and radar, that combinations of transmitters and receivers work better together than alone.

The researchers then used electrodes to measure how the fish's brain responded to these signals. The patterns they found fit well with their models: during group perception, larger brain regions were active, and also more active, than during individual perception. The researchers also showed that fish do not fire their pulses in turn, like dolphins and bats, but rather in a highly synchronized manner. Finally, behavioral tests in an aquarium have demonstrated that the two fish “spawn” more accurately together than individually. Groups of three to five fish in particular had a superior feel together.

To participate




Email the editor