The fossil of a trilobite, preserved for 429 million years, allowed to verify that it had a vision comparable to that of bees and dragonflies today, researchers revealed this Thursday.
Trilobites were arthropods with segmented bodies and exoskeletons and were found in all seas.
These creatures crawled along the ancient seabed of the Paleozoic Era, which lasted until about 252 million years ago, when the Permian-Triassic mass extinction occurred, also known as “Great Dying”, and in which 95% of the species disappeared.
The specimen described in Scientific Reports is less than two millimeters long, with two semi-oval eyes at the back of the head, one of which has not been preserved.
Using digital microscopy, German and British researchers discovered internal structures remarkably similar to those in the compound eyes of modern insects and crustaceans, which see through a mosaic of tiny lenses, separate units that each capture a small amount of light.
“In the case of this small trilobite, the compound eye is almost the same as that of bees, modern day dragonflies and many modern daytime crustaceans,” noted a co-author of the study, Brigitte Schoenemann, from the department of zoology of the German University of Cologne.
“This system seems to be very effective, and also very old,” he told AFP.
Although trilobite eyes had long been known to be composite, older specimens were “slit-shaped,” “just saw straight,” and had no multiple visual units.
“In this type of trilobite, vision is widened, and the eye can also look partially up”he added.
Human eyes have a single lens and tens of millions of light-sensitive cells, providing advanced-level imaging.
Schoenemann explains that in a compound eye, each visual unit works independently by providing a single pixel, “like a computer screen.”
The investigated trilobite had only 200 of these “pixels”, which gave it a mosaic vision, which would allow it to capture “obstacles or lairs” and, more importantly, predators such as the ancient cephalopod, a distant ancestor of the mollusk. nautilus and octopus.
By way of comparison, he pointed out that honey bee it has several thousand of these “pixels”, while a dragonfly up to 30,000 per eye.
“In this way, the resolution is different, but not the functional principle,” he details.
Because each lens in the trilobite’s eye was very small (35 microns in diameter), the researchers induced that it lived in shallow, light-filled water, like some coastal crabs today.
‘Amazing’
This type of trilobite was discovered in 1846 near Lodenice, in the Czech Republic.
Schoenemann said the specimen was not exceptional, thus suggesting that a deeper study of the existing fossils could lead to the discovery of delicate structures that until recently were believed to have disappeared over time.
“I just liked this trilobite with the big head and eyes. But when I looked at it through the microscope, what I saw was amazing. “, he claimed.
“Until recently, it was still believed that only teeth, bones and others could be preserved from fossils, but never cellular structures. Obviously, this has changed ”, he clarifies.
Trilobites began to appear during the call “Cambrian Explosion”, which was an exponential increase in biological diversity that occurred more than 500 million years ago, populating the oceans for about 250 million.
Dinosaurs emerged later and survived about 180 million years.
–
