The ancestors of sharks and stingrays stopped seeing colors about 500 million years ago

Scientists believe that the first fish appeared on Earth about 530 million years ago. Unlike their descendants, they do not have

there were no teeth, no jaws, no solid spine. Some of these primitive features have been preserved in modern sharks and rays.

It is known that sharks appeared approximately 443 millionyears ago, and the remains of the oldest “real” shark, Cladoselache clarkii, 370 million years. Scientists could not restore the appearance and physiological characteristics of ancient sharks from these remains - therefore, the researchers decided to analyze their DNA and compare with the genome of modern sharks.

In the new study, scientists focused onhow the genes for the formation of various types of visual receptors in ancient and modern sharks are arranged. The analysis showed that the common ancestors of cartilaginous fish - that is, sharks and rays - lost polychrome vision back in the Silurian period, about 500 million years ago.

It seems that cone genes that recognizeblue and violet tones, the first cartilaginous fish lost after their ancestors and predecessors of bone fish separated, that is, 460 million years ago. On the other hand, this happened before the first sharks, stingrays and chimera fish arose. This happened no later than 420 million years ago.

Nathan Hart, lead author of the study

Previously, scientists found that the projected increase in ocean acidity levels by 2300 will lead to the destruction of the scales of cat sharks.