Fossil Insect Eyes Composition Surprises Researchers

A natural pigment found in human eyes. Eumelanin is a natural pigment that is found for instance in human eyes. It has been identified for the first time in the fossilized compound eyes of 54-million-year-old crane-flies. It was earlier assumed that melanic screening pigments have no existence in arthropods. But this discovery proved the fact wrong.

"We were surprised by what we found because we were not looking for, or expecting it," says Johan Lindgren who is an Associate Professor at the Department of Geology, Lund University, and also lead author of the study which was published this week in the journal Nature.
The researchers after knowing this, went further on their research so that they can examine the eyes of living crane-flies, and later on found additional evidence for eumelanin in the modern species as well.
The researchers due to their keen research were successful in their study as they by comparing the fossilized eyes with living crane-flies optic tissues, were able to know in detail how the fossilization process worked and they also look close how it has affected the conservation of compound eyes across all geological time.

The fossilized eyes further possessed calcified ommatidial lenses, and Johan Lindgren also believes that this mineral has the power to replace the original chitinous material.
All this left the researchers shocked for a while and forced them to reconsider the another widely spread hypothesis before concluding. Their previous research suggested that trilobites, an exceedingly well-known group of extinct seagoing arthropods, had mineralized lenses in life.

"The general view has been that trilobites had lenses made from single calcium carbonate crystals. However, they were probably much more similar to modern arthropods in that their eyes were primarily organic," says Johan Lindgren.
Compound eyes are generally found in arthropods, such as insects and crustaceans, and are the most common visual organ which is seen in the animal kingdom. They are composed up of multiple tiny and light-sensitive ommatidia, and whatever is the perceived image is, it is a combination of inputs from these individual units.

By: Prerana Sharma
Content: https://www.sciencedaily.com/releases/2019/08/190815101550.htm