Goby fins have fingertip touch sensitivity

November 03, 2020

Groping around in your bag for your keys can be a daily ordeal. I'm not going to list the catalogue of junk in my bag, but I can distinguish every article by touch. Our fingertips are exquisitely engineered, deftly detecting the differences between surfaces and shapes, but we are not the only animals that touch objects. 'A whole host of fishes contact the bottom of bodies of water, plants or other animals using their fins', says Adam Hardy from The University of Chicago, USA, leading Hardy and his graduate advisor, Melina Hale, to wonder whether fish may also be able to feel surface differences with their fins. The duo publish their discovery that goby fins are as touch sensitive as primate finger tips in Journal of Experimental Biology at https://jeb.biologists.org.

However, before they could begin unravelling the question, Hardy and Hale had to find a fish that seems to spend a lot of time in touch with riverbeds and the bottom of lakes. 'Round gobies (Neogobius melanostomus) were a great choice for these experiments given that they are a bottom-dwelling fish that love to perch on rocks and other materials', says Hardy, who biked from the university campus to Lake Michigan during the summer to catch the fish. 'It's always a good day when you can go fishing for work', he chuckles. After collecting a few gobies, Hardy filmed the fish as they manoeuvred over a piece of slate or a wavy piece of plastic on the tank bottom, and also when they wedged themselves against the side of the tank. Sure enough, the fish's fins splayed out over each of the surfaces, contacting the structures like a hand laid upon them. Yet, to find out whether the fins were providing the fish with different touch sensations, Hardy knew he had to record nerve signals from individual fin rays.

Gently brushing a short horizontal bar moving along a fin ray toward the tip at speeds ranging from 5mm/s to 20mm/s, Hardy recorded the electrical signals in nerves as the bar moved over the fin and it was clear that the fins sensed when they were being touched. In addition, each nerve only sensed contact along a tiny portion of each fin ray, possibly allowing the fish to feel fine surface details. But, were the fins sensitive enough to detect the difference between different grades of gravel?

This time, Hardy designed a rotating wheel with 2 mm wide ridges along the edge - separated by gaps of 3, 5 or 7mm - to mimic sediments ranging from coarse sand to granules and pebbles. Then he rolled each wheel along the fish's fin rays at speeds ranging from 20 to 80mm/s. 'It took numerous design iterations to create the wheels', says Hardy, but as he painstakingly recorded the nerve signals produced when the ridges contacted the fin rays, the nerve signals synchronised with each ridge contacting the ray. 'They matched the pattern of the ridges moving across the skin even as the speed of the wheel increased', he adds. Most impressively, the gobies' fins seemed to be as sensitive to the coarse surfaces as monkey finger pads.

'Primates are often held up as the gold standard in tactile sensitivity, so it was really exciting to see that fish fins exhibit a similar tactile response', says Hardy. He and Hale also suspect that the goby's tactical sensitivity may have originated far back in evolution. 'This primate hand-like touch also suggests that the ability to detect surface differences via touch has been around a lot longer than we previously thought', he says.

REFERENCE: Hardy, A. R. and Hale, M. E. (2020). Sensing the structural characteristics of surfaces: Texture encoding by a bottom-dwelling fish. J. Exp. Biol. 223, jeb227280. doi:10.1242/jeb.227280
DOI: 10.1242/jeb.227280

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT permissions@biologists.com THIS ARTICLE IS EMBARGOED UNTIL TUESDAY, 3 NOVEMBER 2020, 18:00 HRS EST (23:00 HRS GMT)

The Company of Biologists

Related Fish Articles from Brightsurf:

Fish banks
Society will require more food in the coming years to feed a growing population, and seafood will likely make up a significant portion of it.

More than 'just a fish' story
For recreational fishing enthusiasts, the thrill of snagging their next catch comes with discovering what's hooked on the end of the line.

Fish evolution in action: Land fish forced to adapt after leap out of water
Many blennies - a remarkable family of fishes - evolved from an aquatic 'jack of all trades' to a 'master of one' upon the invasion of land, a new study led by UNSW scientists has shown.

How fish got onto land, and stayed there
Research on blennies, a family of fish that have repeatedly left the sea for land, suggests that being a 'jack of all trades' allows species to make the dramatic transition onto land but adapting into a 'master of one' allows them to stay there.

Fish feed foresight
As the world increasingly turns to aqua farming to feed its growing population, there's no better time than now to design an aquaculture system that is sustainable and efficient.

Robo-turtles in fish farms reduce fish stress
Robotic turtles used for salmon farm surveillance could help prevent fish escapes.

Heatwaves risky for fish
A world-first study using sophisticated genetic analysis techniques have found that some fish are better than others at coping with heatwaves.

A new use for museum fish specimens
This paper suggests using museum specimens to estimate the length-weight relationships of fish that are hard to find alive in their natural environment.

Reef fish caring for their young are taken advantage of by other fish
Among birds, the practice of laying eggs in other birds' nests is surprisingly common.

Anemones are friends to fish
Any port in a storm, any anemone for a small fish trying to avoid being a predator's dinner.

Read More: Fish News and Fish Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.