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Discussion Starter · #1 ·
Here's my Heart Sea Urchin.


Here's how the Heart Sea Urchin helps clean your sand:

"Locomotion by tube feet but also by movement of the spines on the underside of the body. Sea urchins are generally nocturnal, during the day they hide in crevices. However some sea urchins such as Diadema sometimes form large aggregations in open exposed areas. Despite their sharp spines sea urchins are easy game for some fishes, particularly triggerfishes and puffers. A triggerfish grabs the sea urchin with its hard beak like mouth by the spines or it blows some water towards the sea urchin and turns it on its back. The underside of a sea urchin has much shorter spines and those are easily crushed. During the breeding season the body cavity is crammed with eggs or sperms. This is one of the main reasons urchins are so attractive to fish predators (Japanese also like them for the same reason)."

Echinoderms (starfish, brittle star, sea urchin, feather star, sea cucumber)

I'll have to see if I can find some better info as I didn't add my research to my browser fav's.

Becki
 

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Discussion Starter · #2 ·
"How and what do they eat?
Echinoids feed in two main ways. Regular echinoids graze on macroalgae like kelp (as above). Irregular echinoids deposit feed, either by waiting for particles to settle on their body surfaces or by directly ingesting sediment as in the heart urchins. Sand dollars feed by collecting particles on their body surface and by transferring these to the ventral mouth using their tube feet. Echinoids are very important ecologically as grazers. Ecologists at the University of Sydney have demonstrated that areas called "Barrens" which occur between stands of the kelp Ecklonia are due to echinoid grazing. Manipulative experiments in which echinoids were removed from some areas have revealed that Barrens disappear when echinoids (principally Centrostephenus rodgersii, shown above) are removed. Because the sea urchins are no longer there to eat the kelp, the kelp grows over the barren areas."

Section B - Sea Urchins
 
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