Some Fish Fins Are as Sensitive as a Primate’s Fingertips

Experiments reveal fish fins aren’t just for getting around. They could have implications for underwater robotics

Round goby in a plastic pipe
A round goby (Neogobius melanostomus) in a plastic pipe in the lab. Adam Hardy

New research finds some fishes' fins are as sensitive as the primates' fingertips, reports Carolyn Wilke of Science News.

“We think about primates as kind of special in the sense that we have really exquisite tactile sensitivity, but in fact animals of all types touch objects in their everyday typical behaviors, including fish,” Adam Hardy, a neuroscientist at the University of Chicago and lead author of the paper, tells New Scientist's Donna Lu.

Speaking with Science News, Hardy notes that researchers used to assume fish fins were solely for steering and helping their owners get around.

“There’s a whole host of fishes that live on the bottom [of bodies of water] and routinely make contact with rough and smooth surfaces,” Hardy tells New Scientist. “The ability to sense how those feel can be really important.”

The researchers conducted a series of experiments using fish called round gobies to assess the fish’s ability to detect textures and pressure using their fins. The surprising results were published this week in the Journal of Experimental Biology.

Hardy and his co-author selected round gobies for their study precisely because they are bottom dwellers that are known to perch on rocks and other materials, reports Brooks Hays for United Press International.

The researchers collected gobies from Lake Michigan and brought them back to the lab where they filmed the fish navigating a tank filled with objects of different textures such as a piece of slate or wavy plastic, according to a statement. Hardy and his colleagues saw the gobies brush their fins over the various materials in a manner similar to a person grazing a surface with their hand.

But to get to the bottom of whether the gobies were actually sensing the texture of the object below them with their fins the researchers needed to investigate further. The researchers used rotating wheels covered in precisely spaced ridges and recorded the patterns of electrical impulses sent by the nerves of six euthanized gobies when the rotating wheel brushed against their fins, per the statement. (According to Science News, a saline solution allowed these fin nerves to fire normally even though the gobies were dead.)

The experiments revealed that not only did the gobies’ fin nerves fire when the spinning wheel touched them, but that the pattern of nerve activity corresponded to the speed the wheel was spinning and the spacing of the ridges. This data allowed the scientists to quantify just how sensitive the fish’s fins are.

Speaking with Science News study co-author Melina Hale, a neuroscientist at the University of Chicago, says the goby fins’ “ability to perceive really fine detail … was impressive,” adding that their results looked similar to those reported by other researchers studying the sensitivity of monkey fingertips.

This paper refined the current understanding of how fish navigate their underwater world could provide insights that can be applied to underwater robots, according to Science News. Robots are often designed with separate apparatus for movement and sensing, but, as Simon Sponberg, a biophysicist at the Georgia Tech, tells Science News, “biology puts sensors on everything.”