The round goby has extremely sensitive fins
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Many fish use their fins not just for swimming, but also for sensing pressure or texture – and it turns out that some species’ fins are just as sensitive to touch as the fingertips of humans and other primates.
“We think of primates as special in the sense that we have really exquisite tactile sensitivity, but in fact animals of all kinds touch objects in their typical everyday behavior, including fish,” says Adam Hardy of the University of Chicago.
“There are a number of fish that live on the bottom [of bodies of water] and routinely make contact with rough and smooth surfaces, “he says.” The ability to feel how they feel can be really important. ”
Hardy and his colleague Melina Hale analyzed the ability of the round goby fish (Neogobius melanostomus), a bottom dweller with a soft body, to recognize different textures.
The researchers collected several gobies from Lake Michigan and found that when the fish were placed in a tank they spread their fins over various surfaces, e.g. B. a piece of slate or plastic that was placed at the bottom of the tank. This indicated that the fins had some sensitivity to touch.
To find out how much, the researchers designed rotating wheels with ribs that were 2 millimeters wide on their outer surface, similar to a toothed wheel. The ridges on different wheels were separated by gaps of 3, 5 or 7 millimeters to mimic different textures such as sand and pebbles. The closer the distance, the finer the surface, which would require greater sensitivity of the sensory neurons.
They then rolled the wheels at a speed of 20 to 80 millimeters per second along the fin rays of gobies and recorded whether the wheels triggered nerve signals from individual fin rays – the bony spines in the fins.
At all speeds and comb spacings, the nerves fired in sync with the contact pattern, indicating their sensitivity to fine touch on a spatial scale comparable to that documented in previous studies in primates.
Fish’s ability to feel fine textures can be useful in low visibility conditions like cloudy water, says Hardy.
Journal reference: Journal of Experimental Biology, DOI: 10.1242 / jeb.227280
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