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Starfish eyes are good enough to show them the way home

作者:白篌珩    发布时间:2017-07-20 06:00:18    

DID eyes evolve to guide animals home? Starfish seem to use the light-sensitive organs at the tips of their arms to recognise their reef if they stray from the rocks. The blue sea star (Linckia laevigata) lives on shallow rock reefs in the Indian and Pacific oceans. It has light-sensitive cells in its arms, and prefers to come out at night to graze on algae. What has not been clear, says Anders Garm at the University of Copenhagen in Denmark, is whether the cells simply detect ambient light levels or whether they form spatial images. To find out, Garm collected healthy starfish and removed the arm-tip cells from some of them. When these starfish were placed on the sand near the reef, they scuttled off in random directions trying to get back to safety. Intact starfish, in contrast, always headed directly towards the reef, Garm told the Society for Experimental Biology meeting in Valencia, Spain, last week. Starfish eyes are close to the suggested form for the first image-forming eyes, says Garm. Those first eyes may also have helped identify stationary objects such as a home reef, he says. This article appeared in print under the headline “Starfish eyes show them the way home” More on these topics:

 

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