Holothuroidea
Class Holothuroidea is the sea cucumbers. Superficially, sea cucumbers look like worms. They do not have spines and lack an obvious radial symmetry. Rather, they have what appears to be a sea urchin body plan that has been stretched along the oral-aboral sides. The animal lays on its side where the five rows of tube feet are concentrated. the mouth and anus are on the ends. The endoskeleton is composed of microscopic, calcareous spicules scattered throughout the warty, tough skin.
Many sea cucumbers are deposit feeders. The tube feet around the mouth are modified into branched tentacles that are used to pick up organic matter from the sea floor or scoop sediment into their mouthes. Some sea cucumbers burrow or hide and only extend their tentacles to obtain food directly from the water.
Many sea cucumbers have a very unique defense mechanism. Some secrete toxins, others discharge a sticky, sometimes toxic filament through the anus to discourage predators. Others still, will expell their but and other internal organs through the mouth or anus. This is called evisceration. It is meant to distract the predator and the sea cucumber will eventually grow back the lost organs.
The direct link to the video is http://www.youtube.com/watch?v=lKWSLg5PDiU and you can find it in the assignment folder as well.
Many sea cucumbers are deposit feeders. The tube feet around the mouth are modified into branched tentacles that are used to pick up organic matter from the sea floor or scoop sediment into their mouthes. Some sea cucumbers burrow or hide and only extend their tentacles to obtain food directly from the water.
Many sea cucumbers have a very unique defense mechanism. Some secrete toxins, others discharge a sticky, sometimes toxic filament through the anus to discourage predators. Others still, will expell their but and other internal organs through the mouth or anus. This is called evisceration. It is meant to distract the predator and the sea cucumber will eventually grow back the lost organs.
The direct link to the video is http://www.youtube.com/watch?v=lKWSLg5PDiU and you can find it in the assignment folder as well.