BIO 2135 Lecture Notes - Lecture 16: Water Vascular System, Sea Urchin, Pedicellaria
7 Mar 2017
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Ancient echinoderms developed a unique feeding strategy. Arms and tentacles create an umbrella-like structure. They were at the bottom of the ocean. Things that die float to the bottom. These ancient organisms catch the organic material before it hits the bottom. If you are trapping food and you are sessile radial is the best way to be. Tube feet are on the aboral surface, which line the ambulacral groove. Thanks to tube feet, the echinoderms have a huge surface area to volume ratio for two of its major functions: Ring canal, that hook to radial canals, that hook to lateral canals, that hook to tube feet. Water filled cavity with muscles, ampulla, etc. Contracting muscles = bending the tube foot, changing position. To grip and hold onto the substrate, the suction cup holds it in place (podial muscle controls the sucker) Anus, pyloric stomach, cardiac stomach, digestive gland (pyloric cecum)
