Certainly no creature in the sea is stranger than the common sea cucumber . All living creatures, especially human beings, have their features, but everything about the little sea cucumber seems unusual. What else can be said about an unusual animal that eats mud, feeds almost continuously day and night but can live without eating for long periods, and can be poisonous but is considered eatable? For some fifty million years, in spite of all its strange features, the sea cucumber has lived on its diet of mud. It is adaptable enough to live attached to rocks by its tube feet, under rocks in shallow water, or on the surface of mud flats. Common in cool water on both Atlantic and Pacific shores, it has the ability to suck up mud or sand and digest whatever nutrients are present. Sea cucumbers come in a variety of color1s, ranging from black to reddish-brown to sand-color1 and nearly white. One form even has brilliant purple tentacles . Usually the creature are cucumber-shaped--where their name comes from--and because they live in rocks, this shape, combined with flexibility, enables them to press into crevices  where they are safe from animal eater and ocean currents. Although they have greedy desire for food, eating day and night, sea cucumbers have the ability to become still and live at a low metabolic  rate--feeding a little or not at all for long periods, so that the living things in the ocean that provide their food have a chance to increase by a large amount. If it were not for this natural ability, they would swallow all the food available in a short time and would probably starve themselves out of existence. But the most impressive thing about the sea cucumber is the way it defends itself. Its major enemies are fish and crabs. When attacked, it forces all its internal organs in its body out into water. It also removes attached structures such as tentacles. The sea cucumber will get rid of its organs and grow itself again if it is attacked or even touched; it will do the same if the surrounding water temperature is too high or if the water becomes too polluted. Which of the following can serve as the best title for the passage?
The Variety of Sea Cucumbers. The Sources of Sea Cucumbers. The Strange Creature--Sea Cucumbers. The Similarity of Sea