The acuity of vision was calculated using X-ray tomography and electron microscopy. They are used for feeding and in some species are used by the sea urchin for locomotion. You could say that the entire sea urchin is one single compound eye", said John ******wan, who conducted the study as a part of his doctoral thesis. After all, it&Led Filament Bulbs39;s hardly poor eyesight for an animal with no eyes," John ******wan concluded. The # experiments placed the animals in water inside strongly illuminated cylinders that had various dark images on the walls.John ******wan's calculations showed that of the 360 degrees surrounding the sea urchin an object must take up between 30 and 70 degrees for the sea urchin to see it.

He then registered how large the figures had to be before the sea urchins would defend themselves by directing their spines towards the shadow above."Ordinarily, sea urchins move towards dark areas in order to seek cover. Humans only need an object to take up 0. But the purpose is solved by another of their body part - tentacle-like tube feet.According to a new study conducted by the Lund University, while sea urchins have fairly low-resolution vision - it is good enough to fulfill their basic needs.The study appears in the Journal of Experimental Biology. When I notice that they react to certain sizes of images but not to others, I get a measurement of their visual acuity", explained John ******wan.

John ******wan studied the sea urchin species Diadema africanum."Sea urchins are currently the only animals that have been shown to see without having eyes.Turns out, sea urchins lack eyes.02 degrees in order to detect it, making it clear that their eyesight is poor in comparison with human eyesight.To obtain further data, he carried out another experiment in which he showed rapidly growing figures above the sea urchins, as a way of conjuring up an image of an approaching predator. They see using light-sensitive cells in their tube feet, which resemble tentacles and, like the spines, are all over the body.."However, this is still sufficient for the animal's needs and behaviour. Others are used to attach to surfaces or as levers to correct its position when upside down.The tube feet have other functions besides registering light