Prehistoric armored sea bugs called trilobites that lived nearly half a billion years ago had disco-ball-like-eyes that are remarkably similar to those of modern bees and dragonflies. Trilobites were a marine arthropod with many legs that lived at the bottom of the seafloor during the Cambrian time period (543 million to 490 million years ago) until becoming extinct around 250 million years ago.
Numerous fossils from the sea bug’s strong exoskeleton were discovered by paleontologists and surprisingly its eye was very well preserved. Actually, the remains of the eye were initially found in 1846 close to Loděnice in the Czech Republic but it’s only been recently studied in great detail.
Fossil of a trilobite.
The researchers analyzed the left eye of a type of trilobite called Aulacopleura koninckii from approximately 429 million years ago (pictures can be seen here), specifically the light-sensitive receptor cells in the lenses that suggested a very early evolution of compound eyes. As a matter of fact, trilobites from as far back as 522 million years also appeared to have had compound eyes which suggest that those types of eyes may have evolved a lot earlier than previously thought, maybe in shell-less creatures. Their protruding oval-shaped eyes are situated on the back part of its head.
They studied the eye using microscopy and found hundreds of optical units called ommatidia that make up the compound eyes that are found in today’s insects and crustaceans. According to the scientists, the ommatidia found in the trilobite’s left eye had eight cells that detected light “forming a kind of rosette”. The cells were gathered around a translucent cylinder that channeled light that’s called a rhabdom in addition to there being a thick lens that covered the top of the ommatidia. They also found that the dark-colored rings of pigmented cells created a “cellular basket” surrounding the optical units as well as a thin crystalline cone “although its shape is not very distinct”. You put all of that together and you have a compound eye that looks similar to a disco ball.
3D model of a trilobite.
Based on the fact that the Aulacopleura koninckii’s eye facets were just 0.0001 inches in diameter, the creature would have had a vision of around 200 “pixels” which would have helped it to glide around the waters and avoid predators. It “surely was day active and lived in shallow, light-flooded waters,” Brigitte Schoenemann, who is a paleontologist in the Institute of Biology Education at the University of Cologne in Germany and the lead author of the study, explained in an email to Live Science.
She finished off by stating that today’s insects and crustaceans have vision that is “an enormously old and effective system, quite unchanged since our trilobite”. Things change over the course of hundreds of millions of years but apparently the eyes of crustaceans and insects remained the same. That reminds me of the old saying, “if it isn’t broke, don’t fix it”.
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