doi:10.1038/nindia.2017.94 Published online 31 July 2017
Researchers in Bengaluru have discovered that simple flatworms possess complex visual processing capabilities, including the ability to distinguish colours, and can react to light even after their heads are severed from their bodies1.
Known for their ability to rapidly regrow amputated body parts, planarian flatworms have long been used as models for studying tissue regeneration. But Akash Gulyani and colleagues at the Institute for Stem Cell Biology and Regenerative Medicine decided to focus on their visual function."Our research shows that planarian light sensing is surprisingly sophisticated," Gulyani told Nature India.
These worms that usually live in darkness avoid light with simple reflex-like responses, consistently preferring green over blue and red over green. The study showed they retained the ability to respond to light (ultraviolet but not visible) even when heads were separated from the body — suggesting they have evolved a second way to respond to light that doesn’t involve eyes — and began responding to visible light again as their heads regrew in a week.
"So we have two amazing but very different light sensing networks in one organism: the reflex-like whole body network in headless worms and the eye-brain based network capable of processing in intact worms," says Gulyani. The researchers believe that this switching between eye-brain and whole body response depends on how the regenerating neural networks re-wire and connect to each other. "The exciting thing is we now have a method to visualise this connectivity and competition between the two very different neural networks — all in the same animal," Gulyani says.
The researchers plan to develop planarians as a unique model for eye-brain regeneration and find out how the visual function recovers. They also want to see molecules that control eye-brain regeneration and discover genes/processes that would be of possible biomedical relevance in humans.