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Posts Tagged ‘sea urchin’

Since I didnt attend the field trip, I decided to research sand dollars for my topic. Sand dollars are very interesting. There are sea cookies or snapper biscuit in New Zealand, or the pansy shell in South Africa which refers to species of extremely flattened, burrowing echinoids belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits. Related animals include the sea urchins, sea cucumbers and starfish.They possess a rigid skeleton known as a test. The petal-like pattern in sand dollars consists of five paired rows of pores. The pores are perforations in the endoskeleton through which podia for gas exchange project from the body. The mouth of the sand dollar is located on the bottom of its body at the center of the petal-like pattern. The anus of sand dollars is located at the back rather than at the top as in most urchins, with many more bilateral features appearing in some species. Sand dollars live beyond mean low water on top of or just beneath the surface of sandy or muddy areas. The spines on the somewhat flattened underside of the animal allow it to burrow or to slowly creep through the sediment. Fine, hair-like cilia cover the tiny spines. Podia that line the food grooves move food to the mouth opening, which is in the center of the star-shaped grooves on the underside of the animal . Its food consists of crustacean larvae small copepods, diatoms, algae and detritus

By Marissa Elwell

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