Fish fins aren’t just for swimming. They’re feelers, too. The fins of round gobies can detect textures with a sensitivity similar to that of the pads on monkeys’ fingers, researchers report November 3 in the Journal of Experimental Biology.
Compared with landlubbers, little is known about aquatic animals’ sense of touch. And for fish, “we used to only think of fins as motor structures,” says Adam Hardy, a neuroscientist at the University of Chicago. “But it’s really becoming increasingly clear that fins play important sensory roles.” Studying those sensory roles can hint at ways to mimic nature for robotics and provide a window into the evolution of touch.
The newfound parallels between primates and fish suggest that limbs that sense physical forces emerged early, before splits in the vertebrate evolutionary tree led to animals with fins, arms and legs, says Melina Hale, a neurobiologist and biomechanist also at the University of Chicago. “These capabilities arose incredibly early and maybe set the stage for what we can do with our hands now and what fish can do with their fins in terms of touch.”
Hardy and Hale measured the activity of nerves in the fins of bottom-dwelling round gobies (Neogobius melanostomus) to get a sense of what fish learn about texture from their fins. In the wild, round gobies brush against the bottom surface and rest there on their large pectoral fins. “They’re really well suited to testing these sorts of questions,” Hardy says.