Hyderabad, June 21 (PTI) Researchers at the University of Hyderabad (UoH) have discovered that planar tapeworms can detect light, even without eyes, using an independent eye (extraocular) system lining the periphery of the worm’s body.

Previous research has shown that planarians can survive decapitation (removal of the head) and retain the ability to move away from the light source when exposed to low doses of ultraviolet light, a statement from the UoH.

Researchers are keen to explore the use of these natural light-sensitive proteins to help visually impaired patients “sense” light and control the inner workings of cells / tissues with light (optogenetics), the statement said.

The researchers set out to find out how these organisms perceive light without eyes and is there another light sensing system that helps them detect light.

“In a groundbreaking discovery, a research team led by Dr. Akash Gulyani of the Department of Biochemistry at the School of Life Sciences at UoH showed that an independent eye (extraocular) system lining the periphery of the body The worm allows even a headless flatworm to move like an intact worm with incredible coordination, ”he said.

The researchers found that the worm’s body is dotted with a whole range of very unique light-sensing cells that are spread all over the worm, especially around its periphery, he said.

Oddly enough, these newly discovered photosensitive cells appear unique in that they do not look like any neuron-like cells, but are more like a separate cell class (parenchymal cells) that includes glia-like cells, which are generally thought to have rather support. as a sensory role.

It looks very different from any light sensing system known so far in the animal kingdom, according to the release.

Cells in this independent system of the eye express light-sensitive proteins called opsins that help the flatworm respond to light even in the absence of eyes.

However, the eye independent system responds only to a limited ultraviolet light range of 365 to 395 nm (nanometer), while the eyes of flatworms can detect a wide wavelength of visible light (~ 365 at 625 nm), he said.

Interestingly, the independent eye system only appears in adult organisms, unlike the standard eye set that develops in the embryo.

This discovery of such a set of body-wide light sensing cells that connect to the body-wide nervous system and allow headless worms to move around, may be the discovery of a new type. body-wide organ system to detect light.

Researchers believe the extraocular light detection ability of headless worms may help tailpieces escape light and avoid predators, he said.

The researchers also show that the system helps intact animals respond to sudden exposure to light, even when the animals have gone into a sleep state, helping them avoid predators and danger.

This is again a rare example in the wild where an intact adult animal uses an independent system of the eye to move / escape, despite having a sensitive visual system, according to the release. .

“Taken together, these results provide a unique and astonishing insight into the coexistence, development and evolution of independent light sensing systems in a single organism,” the authors said.

The work is published in the Proceedings of the National Academy of Sciences (USA) .PTI SJR BN BALA BN BALA

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