Phyllophoridae and Synaptidae- Sea Cucumbers

Sea cucumbers are members of the Phylum Echinodermata, which also includes starfishes and brittle stars, sea urchins, sand dollars and feather stars. They have elongate cylindrical bodies with a mouth at one end and an anus at the other. They differ from other echinoderms by having bilateral symmetry instead of a 5-sided symmetry. The oral end of the body is usually surrounded by tentacles. The skin may be leathery or soft, and is often covered with protrusions called tube feet. Their internal skeletons are reduced to microscopic "ossicles" made of calcium that are imbedded in their tissue. Ossicles come in a variety of odd shapes ("tables", "rods", "baskets", "anchors", "buttons", "cups") and are used to distinguish between species. A unique feature of many sea cucumbers is that, when disturbed, they will expel all or part of their guts out through the anus to distract predators. The guts later regenerate.

The respiratory organs of sea cucumbers are located in their anus. They breathe through gas exchange by drawing in and expelling water through their anus. The respiratory organs also double as the excretory organs, expelling waste from the body.