How do echinoderms protect themselves?

Echinoderms are not sought after by many other animals.  Their calcareous skeleton is not terribly appealing to most other animals and in addition, echinoderms have spines, some of which hold toxins.  The tubed feet of some echinoderms can release toxins and the sea cucumber can discharge sticky, entangling threads in which predators can become trapped.  Another defense mechanism of some sea cucumbers is the act of expelling all their internal organs via their anus to either satisfy or confuse their predator.  They can then grow these organs back.