Scientists shed new light into primate eye evolution

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Washington, May 19 (ANI): A recent study has provided a new insight into the evolution of the eyes of primates, taking the example of the nocturnal owl monkey.

Researchers comparing the fetal development of the eye of the owl monkey with that of the capuchin monkey have found that only a minor difference in the timing of cell proliferation can explain the multiple anatomical differences in the two kinds of eyes.

The findings help scientists understand how a structure as complex as the eye could change gradually through evolution, yet remain functional.

The findings also offer a lesson in how seemingly simple genetic changes in the brain and nervous system could produce the multiple evolutionary changes seen in more advanced brains, without compromising function.

Analysis for this study was performed at St. Jude Children's Research Hospital in the US.

"The molecular, cellular and genetic pathways that coordinate proliferation during development have been fine-tuned since the first multicellular organisms emerged millions of years ago," said Michael Dyer, member of St. Jude Developmental Neurobiology.

"When these pathways are deregulated during human development, one of the consequences is childhood cancer. Therefore, by studying how changes in the regulation of proliferation during development can lead to dramatic changes in form and function during evolution, we can gain a deeper understanding of these ancient pathways that lie at the heart of many pediatric cancers," he added.

The owl monkey's eye has numerous adaptations to make it effective for nocturnal function.

For example, it has a greater number of rod photoreceptor cells than the capuchin monkey, which is diurnal (active during the day).

Rod cells are the most light-sensitive cells in the retina making them effective for nighttime vision.

The owl monkey's nocturnal retina is also larger and lacks a fovea, the central region of high-density cone photoreceptors that gives the diurnal eye high acuity and daytime color vision.

For both owl and capuchin monkeys, the specialized cell types in the eye all develop in the growing embryo from a single type of immature cell, called a retinal progenitor cell.

"These two species evolved about 15 million years ago from a common ancestor that had a diurnal eye," Dyer said.

"So, we believe that comparing how their eyes develop during embryonic growth could help us understand what evolutionary changes would be required to evolve from a diurnal to a nocturnal eye," he added. (ANI)

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