Scientists Decode 'Eyespots': Why Some Rays Have Fake Eyes While Others Stay Hidden
The study suggests that eyespots in skates and rays evolved as anti-predator defences, appearing mainly in shallow-water species lacking strong physical weapons.
Published : April 25, 2026 at 7:05 PM IST
Hyderabad: You may have noticed bold circular "eyespots" on some creatures, ranging from butterflies to peacocks. Some species of skates and rays also have these distinct markings. It turns out they are the result of evolution and are part of anti-predator defences.
Researchers from Stockholm University, Sweden, examined more than 580 species of skates and rays to find the reason behind these marks across the ancient group of cartilaginous fishes. Instead of studying the eyespots in isolation, they analysed multiple anti-predator defences together to map the evolutionary history of these marks.
Their findings, published in Nature Ecology & Evolution, explain why some of these dramatic visual signals appear in some groups while being absent in others.
"Eyespots evolve only under certain ecological and defensive conditions. They are one solution among many in the evolutionary arms race between predator and prey," said lead author Madicken Åkerman.
According to the study, the species that possess weapons like powerful electric organs or venomous spines to defend against predators rarely evolved conspicuos marking. Meanwhile, the group which mainly relied on camouflage to hide for survival were more likely to develop bold spots or eyespots, particularly if they lived in well-lit, shallow waters less than 200 metres deep.
"Eyespots are far from random," said senior author John Fitzpatrick. "They tend to evolve in species that lack strong physical defences, such as venomous tail stings or electric shocks, and that live in bright, shallow waters where visual signals are effective."
As per the study, the eyespots almost never evolved directly but have a history in evolution. The species typically first gained simpler markings, such as bold spots, which were later refined into the classic concentric-ring eyespots seen in some skates.
"It appears to be a stepwise process," said Fitzpatrick. "Other markings come first, and over time they refine into eyespots."
Another interesting thing the study highlights is that the markings are also frequently lost, which is also tied to the defensive mechanism. In deep, dark waters where little light penetrates, a visual signal cannot be seen and hence does not offer protection. The study suggests that under those conditions, the cost of being conspicuous outweighs the benefit, and this is why the marking disappears.
