Scientists Discover Mysterious Sea Creatures That Have Thousands of Eyes

SIDNEY – Chiton, sea ​​animal small with a shell, unique compared to other creatures in the animal world. This animal has thousands of tiny, round eyes embedded in its segmented shell.

These eyes, called ocelli, are made of the mineral aragonite and although small and primitive, are believed to be capable of seeing clearly, distinguishing shapes and light.

However, some chiton species have “eyespots” that are smaller and function more like individual pixels, similar to the compound eyes of insects or mantis shrimp. These eyespots form visual sensors distributed throughout the chiton’s shell.

A new study examining the origins of the chiton’s distinct visual system has revealed a remarkable evolution in these rock-dwelling animals. Their ancestors developed eyes four times in two different ways, resulting in two very different types of visual systems today.

This research shows how evolution presents different solutions to fundamental problems, such as how to use light to escape predators. This is similar to crabs and their side-walking body shape, which has evolved at least five times.

“We know that there are two types of eyes, so we don’t expect four independent origins,” said evolutionary biologist and lead author of the study, Rebecca Varney from the University of California Santa Barbara as reported by Science Alert, Sunday (17/3/2024 ).

“The fact that chitons developed eyes four times, in two different ways, is truly amazing to me.”

Researchers reconstructed this evolutionary history by comparing fossils and analyzing DNA samples from specimens at the Santa Barbara Museum of Natural History. The results show that the two visual systems evolved twice sequentially.

Surprisingly, chiton groups with similar visual structures are not the most closely related. They are distant relatives separated by millions of years.

Species with fewer gaps in their shells tend to evolve fewer and more complex shell eyes.

Chitons with more gaps later develop more numerous and simpler eyespots.

The researchers concluded that the role of trait history in shaping evolutionary outcomes is critical to understanding how and why traits can evolve in predictable ways.

(wbs)