Some fish, it turns out, can “beam” sensory information to other nearby fish to expand their detection range. Working with African electric fish – also known as elephantnose fish, the team, at Columbia University, discovered that the animals use electrical receptors in their bodies to detect external signals as electrical images that are then shared themselves, allowing them to see things. as a group and farther than they could manage alone. Sannia Farrukh heard from the head of the study, Nathaniel Sawtell…
Nathaniel – We created a computer model of the electric fish and its field, and then we could put objects and other fish in different configurations and then look at the electrical images on the skin of the fish. So we can use the model to calculate or visualize how the electrical field of the fish interacts with objects. And we can do this under conditions when the fish is alone or when it is in a group. And what we found from these simulations is that when fish are in groups, they can get more information about their environment. And specifically, what intrigued us was that in groups, fish actually see farther. So something that is out of electro location range for the fish when it is alone, can be seen very clearly by the fish when another nearby fish is also emitting electrical pulses.
Nathaniel – So this idea that came out here is that electric fish can amplify their electric sensing in groups. So we first saw this in the model, and then what we saw in the brain was that when two fish were close to each other, we saw electrical signals in the brain of the fish or neural signals in the brain of the fish related not only to the fish’s own pulse, but to the pulse of nearby fish. So when the fish are alone, we see this very limited range. But when we added electrical pulses to the water, mimicking those from other fish, we saw that the sensing range was dramatically improved. So it increases by a factor of two or even a factor of three in some cases.
Sannia – I’ve seen this dubbed as telepathy. Is this a fair comparison or is it more a case of the group electric effect? Like how do swarms of bees create bigger electricity bills?
Nathaniel – It’s definitely not visible to us. So these electrical fields are emitted by the fish. We don’t see them, we don’t feel them. They travel at the speed of light. So they certainly have magical properties, but they’re electric fields, the same kind of fields, you know, that we encounter when we turn on a light switch. But it is remarkable in such a way that the fish release this energy into the water and then other animals nearby benefit from that energy. That energy conveys information to the entire group at almost the same moment.
Sannia – So do you think there might be other species with that ability?
Nathaniel – In terms of other active sensing animals? The most studied are bats and dolphins, both of which use echolocation to sense their surroundings. Researchers studying those animals have thought and wondered about these same issues. What happens when bats are in a group or dolphins are in a pod? Are the emissions of other animals a source of interference or can they help? There is some evidence in those systems that jamming can be a problem. There is little evidence that animals can really feel as a group. So this is something that needs to be investigated further. And we think our studies showing that electric fish can sense as a group can motivate more studies of these other animals.
Sannia – So what are the next steps of this study? Will you look at the neural mechanism?
Nathaniel – We are really interested in the neural mechanism. And it’s, you know, it’s worth noting that the fish that we’re studying have very large brains. So their brain to body mass ratios are bigger than real people. And their brains developed in a very interesting and unique way. The large brains of humans are dominated by the cerebral cortex, which has grown to cover the entire brain in these fish, a different part of the brain. The cerebellum is the dominant part of the brain that covers the entire surface of the brain and makes it very large. So we often wonder what kind of intelligence these animals have that rely on the cerebellum. In particular, one possibility that this work suggests is that these animals use the cerebellum to make sense of this information that they receive in groups. And one thing you can imagine is that in order to feel in a group, you need to have a very good knowledge of the members of your group.
Nathaniel – And you might even have to guess how they move in space and track that. Then again, since these fish do all of this in dark, murky rivers without the benefit of much eyesight, you have to have some pretty sophisticated skills to track fish in a group. And then all these studies, of course, were done in the laboratory setting and the settings were somewhat reduced. So we are very curious about what is the true ecological function of this group felt in the natural habitats of these animals? Do fish really actively change their behavior? Do they position themselves in a way that makes this feel better? Do they coordinate the timing of their pulses? So the degree of social coordination and cooperation is another fascinating open question that we will pursue.
