Trilobites – the stunning, half-billion-year-old armored sea bugs – have eyes that are faceted like disco balls. Today, new images reveal that these eyes are similar to bees and dragons.
Trilobites are like the blue, multi-footed sea arthropods that appeared during Cambrian period (543 million to 490 million years ago) and died nearly 250 million years ago. Paleontologists have found many fossils of the poor exoskeleton of trilobites. And while trilobite eyes are also preserved and have a resemblance to the surface of the eyes of insects, the previous analysis was written on their complexity.
Now, for the first time, researchers have described the internal structures that make up trilobite eyes Aulacopleura koninckii, who lived about 429 million years ago. The composition and arrangement of light-sensitive receptor cells in these lenses offer scientists a glimpse into trilobite vision, and brought about the early evolution of compound eyes.
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Although the specimen was collected in 1846 near Loděnice in the Czech Republic, this was the first time his eye had been recorded using microscopy. This technique revealed optical units called ommatidia, hundreds of which make up the eye compounds in modern crustaceans and insects.
Diagnosis of small trilobite eyes is difficult; A. koninckii is “rather flat” – about 0.04 inches (1 millimeter) high, scientists reported in a new study, published online online (August 13) in the journal Scientific Reports. In this species, two protruding eye-shaped eyes are located at the back of the head and are particularly vulnerable to injury; only the left eye of the specimen was still intact when the researchers found it.
Sa compound eyes, individual lenses – sometimes thousands of them – process visual input and send signals to the brain, working together to form a mosaic of images. And inside a single trilobite eye, the study authors found structures still present in modern arthropod eyes.
Each of the trilobite ommatidia contains eight light-seeing cells that form a kind of rosette, “the scientists wrote. The cells are grouped around a translucent, light-channeling cylinder called that a rhabdom, and a thick lens covered the ommatidia at the top, the scientists wrote.The dark rings of the pigment cells formed a “cellular basket” around the optical units, and there is some evidence of a thin, crystalline cone, “although its shape is not very unique,” according to the study.
The study found that together, these structures formed “a classical compound of the eye compound,” which looked like a disco ball. This type of compound eye is found in day-active insects and crustaceans, such as bees and dragons.
A. koninckii is an underground residence, walks on the surface of the sea and strengthens particles of organic material. The diameter of the facets, or ommatidia, also told scientists about the habitat of the trilobite, said lead study author Brigitte Schoenemann, a paleontologist at the Institute of Biology Education at the University of Cologne in Germany.
Eye compounds with large ommatidia help animals navigate mild conditions. But A. koninckiiEyesight is measured by only 0.001 inches (35 micrometers) – in smaller parts for compound eyes. This means that the trilobite “is definitely day active and lived in shallow and submerged waters,” Schoenemann told Live Science in an email.
The number of facets in each eye gave A. koninckiiThe mosaic vision of a “resolution” of nearly 200 “pixels,” which would be sharp enough for it to navigate barriers and prevent cephalopod predators, he said.
Even the earliest trilobites, dating to 522 million years ago, show signs of having compound compound eyes, Schoenemann said. This type of eye is likely to have emerged earlier, perhaps in shell-less creatures that do not fossilize, he added.
The findings of scientists show that the vision of the most modern insects and crustaceans of the sun “is an enormously old and effective system, which has not changed since our trilobite,” Schoenemann said.
Originally published in Live Science.