Earlier this year, planarian flatworms had travelled farther than most humans did--they went to space! And they even came back with a surprise: each had then two heads! Now, such small worm gets to amaze us one more time with their newly found ability.
Researchers from India had two studies on the species Schmidtea mediterranea, with both focusing on the worms' visual mechanism. These flatworms live in a dark, moist environment and so have evolved vision that doesn't require lens.
So, in the first study, they shined either blue or red light over the flatworms. And results showed the they actually tend to prefer the red light and move towards it. But this doesn't necessarily mean that they can see colors for their eyespots lack wavelength-specific photoreceptors. Instead, researchers hypothesized that the flatworms just compare the amount of light that’s absorbed by the eyespots.
The second study, on the other hand, showed that the decapitated flatworms still respond to light. More specifically, they reacted to ultraviolet and not the visible light. It is only 12 days after decapitation when the flatworm responded back to visible light.
This happens because flatworms actually have two types of vision--one through the eyespots, and the other through its body reflexes. But the latter still needs more exploring.
The researchers also speculated that flatworms' instinctual response to ultraviolet light may be an ancient mechanism while the response to visible light as a later acquired evolution. That is, flatworms' UV response is a reflex and its later reaction to visible light is brain-controlled already. “It’s a fascinating coincidence that decapitation-regeneration experiments appear to copy – chronologically, at least – what may have occurred in evolution,” says Gulyani.
Sorry, dear worms, you're really amazing. But we still have to constantly cut you off for the sake of science.
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