Wednesday, January 4, 2012

A scorpion can use its whole body as eyes

Scientists have just discovered a remarkable feat of scorpions. While they possess as set of eyes just like we humans do, they appear to have an additional one: their whole body functions as an eye, apparently. They seem to be adept in picking up ultraviolet light, something we cannot even see with our own eyes.

Scorpion experiments
The researchers, studying at California State University, illuminated a scorpion cage with either visible light or UV light, and made scorpions wear objects that blocked their ordinary vision. Under normal light, the scorpions did not move much, but when illuminated with UV light, they moved around as if they were able to observe their surroundings. Because they moved in the same fashion with and without vision-blocking glasses, they appear to have no need for actual eyes when their cage is illuminated by UV light.

It is peculiar that evolution favoured picking up UV light with the body, as it does not seem to be a very useful feat for scorpions that already possess a set of eyes that specialize in capturing visible light. The only other animals known to pick up light with their bodies are fruit fly larvae. More study is required to find out what purpose bodily UV detection serves. It is likely that the scientists will start by uncovering the actual mechanism behind observing UV light.

The third eye
Though most people are not aware of it, there is something which often referred to as 'the third eye', located just below our skull. It is actually an endocrine gland that produces a hormone that helps set our daily rhythm. In some vertebrates, the pineal gland is able to respond to visible light as some sort of third eye, which helps set the circadian rhythm, but it is not known exactly whether ours also responds to light. Because blind people do have a circadian rhythm, it hints at pineal gland involvement.

Discovering that scorpions detect UV light with their bodies does not seem as useful as discovering new drugs to cure cancer. Nevertheless it is an interesting piece of knowledge, considering the fact that we have long thought that animal species have a skin to protect them from the outside world. Perhaps we discover more species that have a bodily eye, and uncover an evolutionary mechanism that explains why bodies need to be able to detect UV light.

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