living in bottom of sea in burrow body and is soft and fragile
Answers
Sea urchins or urchins are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth .... while the sides are devoid of tube feet. This "irregular" body form has evolved to allow the animals to burrow through sand or other soft materials.The sea cucumber is not exactly the beauty queen of the seas. Named for the long, tubular vegetable with a clean smell and a crisp flavor, the animal looks more like a pickle with an unmentionable skin disease. It crawls along the bottom of sandy floors; depending on the species, it can look like a ridged, knobbly, or even spiked giant sea slug. The animal has no brain—just a ring of nerves around its oral cavity that extend both to the tentacles around its mouth and also down the length of its body. It gobbles up the detritus that falls to the seafloor, extending long tendrils that are modified versions of the tube feet it shares with starfish. Depending on the species, these feeding tube feet can be gorgeous and ornate, like the branches in a tree or the delicate ends of a neuron.