{"id":294086,"date":"2010-02-08T13:15:52","date_gmt":"2010-02-08T18:15:52","guid":{"rendered":"http:\/\/blogs.discovermagazine.com\/discoblog\/?p=6577"},"modified":"2010-02-08T13:15:52","modified_gmt":"2010-02-08T18:15:52","slug":"eyeless-urchins-%e2%80%9csee%e2%80%9d-the-sea-with-their-spines-discoblog","status":"publish","type":"post","link":"https:\/\/mereja.media\/index\/294086","title":{"rendered":"Eyeless Urchins \u201cSee\u201d the Sea With Their Spines | Discoblog"},"content":{"rendered":"

\"urchin\"Oh, you. You think you\u2019re pretty fancy, don\u2019t you, with your matching pair of eyeballs, your precious optic nerve, your oh-so-sophisticated visual cortex. You think you\u2019re so<\/em> evolved.<\/p>\n

The sea urchins are not impressed.<\/p>\n

Though the round, spiny marine creatures have no actual visual organs, they do have light-sensitive proteins that help them \u201csee\u201d well enough to move around, find shelter and avoid predators (well, at least the slow ones<\/a>). Biologists now think that a sea urchin\u2019s entire body functions as one big compound eye<\/a>, where photosensitive tissue inside the exoskeleton picks up light that\u2019s filtered by the radiating spines. And the denser an urchin\u2019s spines, the sharper its perception of its surroundings, a new study<\/a> suggests. So who\u2019s fancy now?<\/p>\n

<\/span>S\u00f6nke Johnsen<\/a> and his team at Duke University in Durham, N.C., tested the visual responses of Strongylocentrotus purpuratus<\/em>, a large, purple Pacific urchin with an especially spiny exoskeleton. They placed individual urchins in the center of a tank with a dark target on one side, and they lit the tank from above.<\/p>\n

In under a minute, the urchins began to move relative to the target. Some inched toward the dark spot and others scooted away from it, but their trajectories were definitely deliberate\u2014each urchin was tested four times with the spot in different parts of the tank, and each repeated its behavior every time.<\/p>\n

\u201cEven though the group as a whole did not choose one direction relative to the target, they obviously responded to it,\u201d the researchers wrote in The Journal of Experimental Biology<\/em>. \u201cThis is analogous to a group of people each using their own compass to go a different direction.\u201d<\/p>\n

According to Johnsen\u2019s team, it\u2019s possible that urchins who were attracted to the spot interpreted it as a cave to hide in, while the ones who fled treated it as a predator like an eel<\/a> or a sea star.<\/p>\n

S. purpuratus<\/em> could detect smaller targets than a previously tested species<\/a> with sparser spines, suggesting to the researchers that the additional spines give it greater visual resolution. They say they\u2019d need to test additional species to be sure.<\/p>\n

Okay, so they still can\u2019t recognize<\/a> faces<\/a> or appreciate the subtleties of a Van Gogh, but Johnsen and his colleagues say the urchins can see about as well as a horseshoe crab<\/a> or chambered nautilus<\/a> \u2014 and those guys have actual eyes. Not bad, right?<\/p>\n

At least one urchin species, by the way, can live up to 200 years<\/a>, so don\u2019t even think that you\u2019ll win in a stare down.<\/p>\n

By Mara Grunbaum<\/a>. This article is provided by Scienceline<\/a>, a project of New York University\u2019s Science, Health and Environmental Reporting Program.<\/em><\/p>\n

Image: Wikimedia Commons<\/a><\/em><\/p>\n

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Oh, you. You think you\u2019re pretty fancy, don\u2019t you, with your matching pair of eyeballs, your precious optic nerve, your oh-so-sophisticated visual cortex. You think you\u2019re so evolved. The sea urchins are not impressed. Though the round, spiny marine creatures have no actual visual organs, they do have light-sensitive proteins that help them \u201csee\u201d well […]<\/p>\n","protected":false},"author":641,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-294086","post","type-post","status-publish","format-standard","hentry","category-news"],"_links":{"self":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts\/294086","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/users\/641"}],"replies":[{"embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/comments?post=294086"}],"version-history":[{"count":0,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts\/294086\/revisions"}],"wp:attachment":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/media?parent=294086"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/categories?post=294086"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/tags?post=294086"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}