Our fingertips can tell us a lot about our environment.
But it looks like we're not the only ones who use "fingertips" to learn about our surroundings.
A recent study from the University of Chicago has revealed some surprising new information about the sensory capacity of fish fins. Scientists in the University's Organismal Biology and Anatomy Department found evidence of touch-sensitive neurons and cells in the pectoral fins of the pictus catfish.
The study author, graduate student Adam Hardy, along with mentor Dr. Melina Hale and Professor William Rainey Harper, designed an experiment around a simple question: can fish fins sense touch?
To answer this question, the scientists focused their efforts on the pictus catfish, a small, bottom-dwelling, Amazonian species. Based on high-speed camera analyses, the scientists confirmed that unlike many other fish, the pictus catfish does not appear to use its pectoral fins for movement.
This fact allowed the researchers to isolate the sense of touch from that of proprioception (an awareness of where the body is in space) in an experimental setting. Because the pictus catfish's fins are non-locomotive, the scientists were able to hone in on touch-generated neural activity without having to deal with conflicting signals about the movement and position of the fins.
In order to isolate and study touch-generated neural activity in the catfish, the scientists touched the pectoral fins with the flat end of a pin, and with a brush. They studied the neural response to the various stimuli. What they found was that the neurons both responded to contact with the foreign objects and also conveyed to the brain information about the details of that contact, such as the amount of pressure the brush exerted.
"It was a surprise to us that, similar to mammalian skin, fish fins are able to sense light pressure and subtle motion...This information seems to be conveyed by a type of cell important for touch in mammals, which suggests that the underlying sensory morphology may be evolutionarily conserved," Hardy said.
The researchers discovered that the pectoral fins of the pictus catfish are home to receptor cells that behave in a way similar to the touch-sensitive Merkel cells found in the skin of mammals. It is an important discovery.
"It raises a lot of exciting questions on how sensory cells shape the brain's perception of environmental features and may provide some insight into the evolution of sensation of vertebrates," said Dr. Melina Hale.
The team is now studying other species of fish to determine whether or not a sense of touch is unique to the fins of the pictus. In addition, the researchers believe their findings could eventually lead to important developments in underwater robotics.
Want to learn more? Check out the University of Chicago Medical Center's news release about the experiment here.