Worms can see light without eyes and with their heads cut off

Planarians are a type of flatworm, soft-bodied creatures lacking complex organs. They have two eyes

which connect to the centralized beamganglion in the head. They act like the brain, and the eyes themselves are sensitive to ultraviolet light. In the presence of UV light, the worms use their cilia—tiny hair-like structures on their bodies—to navigate in space.

In a new study, scientists found thatsmall worms only a few millimeters long do not need their eyes or brains to detect light. When the researchers cut off the heads of the planarians, the worms were still able to perceive ultraviolet light.

Removing the animal's head may appeara strange way of doing behavioral experiments. But planaria are known not only for surviving decapitation, but also for easily repairing missing body parts. Amputation is not a problem for planaria. If you cut one of them into several pieces, then each piece turns into a new worm, according to the Max Planck Institute for Molecular Biomedicine in Münster, Germany.

In a new study published in the journalProceedings of the National Academy of Sciences (PNAS), researchers discovered that planarian bodies contain cells that produce a light-sensitive protein called opsin. Arrays of these cells, found along the periphery of the worms' bodies, expressed two opsins - NC R-opn 1 and NC R-opn 2. At the same time, more centrally located cell populations expressed only NC R-opn 1.

Researchers have found that cellsproducing only one opsin are pigmented. In peripherally located cells, two opsins first captured UV light and then triggered the movement of the headless worm. The light wriggled in response to this. At the same time, scientists note that only adult worms had a photosensitive superpower.

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