Catholic Online (www.catholic.org)

Even with the absence of eyes, some creatures have light-sensitivity that uses the same visual pathway that allow us human beings to see.

SANTA BARBARA, CA (Catholic Online) - Todd Oakley, professor in UCSB's Department of Ecology, Evolution, and Marine Biology, helped write a paper about the behavior of hydra, a freshwater polyp. Hydra, along with jellyfish, sea anemones, and corals are part of the family, Cnidaria, which use stinging cells to catch prey. The tentacles of a hydra contain barbed, poisonous stingers that stun very small animals. The tentacles are also used for transportation as well as self-defense.

"Hydra stinging cells were already known to be touch sensitive and taste sensitive, but no one had ever thought before to look for light sensitivity -- probably because they don't have eyes," Oakley said. "We're the first to have found that. And we found not only that light-sensitivity genes are expressed near hydra stinging cells, but that under different light conditions, these cells have different propensities to be fired."

According to research, it is discovered that bright light actually initiates the firing of the stinging cells. The light may act as a daily, rhythmic cue that tells the hydra when to sting. Hydras contain sensory neurons required for phototransduction, which humans use. In phototransduction, light is converted to electric signals.

"I wouldn't call this vision, because as far as we know the hydra are not processing information beyond what's light and what's dark, and vision is much more complicated than that. But these genes that we're studying are the keystones of vision," Oakley said. "For us, as evolutionists, the message is that photoreception can do other things besides just facilitate vision. It can do unexpected things. What good is half an eye? Even without eyes there are other functions for light sensitivity that we may not be thinking of."

© 2012, Catholic Online. Distributed by NEWS CONSORTIUM.

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