This fish uses 'skin vision' to look at itself from the inside

A new study has suggested that hogfish don't just see with their eyes, they also see with their skin. The study published in Nature on Tuesday (August 22) said that hogfish known for its colour-changing skin, can morph from white to mottled to reddish-brown in a matter of milliseconds to blend in with corals, sand or rocks. They have light-sensing skin or skin vision, which helps them to see their surroundings.

These fish are not only using skin vision to see their surroundings, as biologist Lorian Schweikert says that the fish could be using skin vision to view themselves.

The discovery

Add WION as a Preferred Source

A few years ago, during a fishing trip, Schweikert came across a hogfish and threw it onboard. But later when she went to put it in a cooler she noticed something odd: its skin had taken on the same colour and pattern as the deck of the boat. The biologist was surprised as this fish continued its camouflage even though it was no longer alive. “That opened up this whole field for me,” Schweikert said, according to a report by Eureka Alert.

In 2018, Schweikert and another biologist Sonke Johnsen published a study that showed that hogfish carry a gene for a light-sensitive protein called opsin that is activated in their skin and that this gene is different from the opsin genes found in their eyes.

In the study published on Tuesday, Schweikert, Johnsen and their colleagues took a closer look at the hogfish's skin. The researchers took pieces of skin from different parts of the fish’s body and took pictures of them under a microscope.

Up close, the skin looked like a pointillist painting. Thestudy added that each dot of colour is a specialised cell called a chromatophore containing granules of pigment that can be red, yellow or black.

The movement of these granules changes the skin colour. When granules spread out across the cell, the colour appears darker. And when they cluster together into a tiny spot, the cell becomes more transparent.

An internal polaroid film

The hogfish's light-sensitive opsins act somewhat like an internal polaroid film. “The animals can literally take a photo of their own skin from the inside,” biologist Johnsen said, according to Eureka Alert. “In a way, they can tell the animal what its skin looks like since it can’t really bend over to look,” he added. “Just to be clear, we're not arguing that hogfish skin functions like an eye. We don't have any evidence to suggest that's what's happening in their skin,” Schweikert, meanwhile, said.

Rather, it’s a sensory feedback mechanism that lets the hogfish monitor its own skin as it changes colour, and fine-tune it to fit what it sees with its eyes.

WATCH WION LIVE HERE

You can now write for wionews.com and be a part of the community. Share your stories and opinions with us here.