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The Evolution Of Eyes

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http://www.nature.com/news/2004/041025/full/041025-18.html

Marine worm sports two kinds of 'eyes'
Vertebrate and insect vision may have evolved from the same precursor.

Darwin famously realized that the eye would be a key test for his theory of evolution by natural selection. He suggested gradual steps from an "imperfect and simple" form, and modern scientists have no trouble believing that the eye evolved from a single light-detecting cell. But they disagree over whether it evolved just once, or many times.

Now the miniscule marine worm Platynereis dumerilii, whose crude light perception seems to have stood it in good stead for millennia, hints at an answer to this question.

Its few light-sensing cells come in two types: one is of a type seen almost exclusively in vertebrates, and one is seen in insects, according to a paper in this week's Science1. Could a worm like Platynereis have been the father of the eye? ...
 
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Interesting but, not being a biologist, i can't find the critical information detailling (or even speculating) over the respective benefits of each type of photoreceptor: the insects' Rhabdomeric or Ciliary cells of the vertebrate.

Not 100% convinced, further research etc.

It's always going to remain speculation until we have a more certain narrative of this worm's evolution. I'd add, somewhat hazily, that having both type of photoreceptors is a sufficient but not a necessary condition for the human eye to have a single progenitor.
 
Newly published research indicates certain trilobites evolved hyper-compound eye structures with multiple optic neural connections - a configuration previously unknown in any animal (of any era).
This trilobite was equipped with a 'hyper-eye' never seen before in the animal kingdom

The humble trilobite, a helmet-headed creature that swam the seas hundreds of millions of years ago, was hiding an extraordinary secret — a "hyper-eye" never seen before in the animal kingdom.

By poring over X-ray images, researchers found that certain species of trilobite — extinct arthropods distantly related to horseshoe crabs — had "hyper compound eyes," complete with hundreds of lenses, their own neural network to process and send signals and multiple optic nerves, according to new research published Sept. 30 in the journal Scientific Reports. ...

Today's arthropods, like dragonflies and mantis shrimp, are also known for their powerful compound eyes, which are composed of myriad eye facets called ommatidia, each equipped with its own lens, like a disco ball. ...

But, according to the new findings, trilobites from the family Phacops had compound eyes that were far larger and more complex than their modern-day arthropod relatives. Each of their eyes (they had one on the left and one on the right) held hundreds of lenses. At nearly a millimeter across, these primary lenses were thousands of times larger than a typical arthropod's. Nestled beneath them like bulbs in a car headlight sat six (or more) faceted substructures akin to a typical compound eye. "So each of the big Phacopid eyes is a hyper compound eye with up to 200 compound eyes each," study lead author Brigitte Schoenemann, a paleontologist at the University of Cologne in Germany, told Live Science ...
FULL STORY: https://www.livescience.com/trilobite-eyes
 
Here are the bibliographic details and abstract from the published study. The full report is accessible at the link below.

Schoenemann, B., Clarkson, E.N.K., Bartels, C. et al.
A 390 million-year-old hyper-compound eye in Devonian phacopid trilobites.
Sci Rep 11, 19505 (2021).
https://doi.org/10.1038/s41598-021-98740-z

Abstract
Trilobites, extinct arthropods that dominated the faunas of the Palaeozoic, since their appearance c 523 million years ago, were equipped with elaborate compound eyes. While most of them possessed apposition compound eyes (in trilobites called holochroal eyes), comparable to the compound eyes of many diurnal crustaceans and insects living today, trilobites of the suborder Phacopina developed atypical large eyes with wide lenses and wide interspaces in between (schizochroal eyes). Here, we show that these compound eyes are highly sophisticated systems—hyper-compound eyes hiding an individual compound eye below each of the big lenses. Thus, each of the phacopid compound eyes comprises several tens, in cases even hundreds of small compound eye systems composing a single visual surface. We discuss their development, phylogenetic position of this hyper-compound eye, and its neuronal infrastructure. A hyper-compound eye in this form is unique in the animal realm.

SOURCE / FULL ARTICLE: https://www.nature.com/articles/s41598-021-98740-z
 
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