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A 390-million-year-old fossilized trilobite has revealed troubling secrets about large marine arthropods – they had eyes like no other animal ever discovered. What appeared to be two separate eyes, as scientists would expect, were actually large systems of hundreds of individual lenses that all formed their own mini-eyes. That is, these animals had hundreds and hundreds of eyes.
Behind each lens was a series of facets anchored by photoreceptors and a network of nerve cells, capturing light from each before sending it to the brain through a central optic nerve, creating what can only be seen as one way very unique to see the world. . The research was published in the journal Scientific Reports.
To make the discovery, the researchers analyzed a series of x-ray photographs taken of the extremely well-preserved fossil in the 1970s. The photos, taken by amateur radiologist and paleontologist Wilhelm Stürmer, showed clear filaments under the eyes and suggested that ‘it was about nerves, while proposing that these specific trilobites have a series of sub-facets (small areas of photoreceptors that make up a compound eye, like the tiny hexagons you can see on a fly’s eye) under each eye that contributed to the overall structure. Scientists at the time rejected this interpretation. Today, 40 years later, modern technology allows scientists to realize that Stürmer was right.
The fossil belongs to a suborder of trilobites, called Phacopinae. While other trilobites have eyes comparable to those of a modern fly – the hexagonal facets form a large compound eye, and under each facet are eight photoreceptors that capture light – this suborder takes a different approach. Each compound eye contains 200 lenses, much further apart than the other examples of compound eyes, and under each are six sub-facets.
“Each of these eyes consisted of around 200 lenses up to 1mm [0.04 inches] in size, ”lead researcher and zoologist Dr Brigitte Schoenemann said in a statement.
“Under each of these lenses, in turn, at least 6 facets are configured, each of which again constitutes a small compound eye. So we have about 200 compound eyes (one under each lens) in one eye.”
These all contribute to a “hyper eye”, which may have given Phacopinae a distinct advantage over other animals. Their numerous lenses and complex eye systems may have enabled them to detect tiny changes in light in low light conditions, giving them an advantage in hunting prey (such as the hard-shelled animals they have run over and stabbed to death with their paws) or hide from large predators. It is also possible that certain areas of the hyper eyes have different functions, such as enhancing contrast.
Stürmer, sadly, passed away in the 1980s, so he would never receive the validation he deserved for revealing a unique ocular structure 40 years before others could.
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