Euapta lappa

The beaded sea cucumber, Euapta lappa, is a member of the family Synaptidae within the phylum Echinodermata. It lives on coral reefs in the Caribbean region.

This species looks more like a long worm than a typical sea cucumber. It can grow up to a meter in length and about 4 centimeters wide. Its body is normally soft and floppy, but when startled, it contracts violently to a much shorter length. It lacks both tube feet and an internal respiratory tree.

The skin is covered in rounded ridges, and embedded in the cuticle are many tiny calcareous plates called ossicles. Small hooks on these ossicles make the body feel sticky. At the front end is a ring of fifteen branched tentacles used for feeding. The body color is pale brown or gray, often with white flecks, darker streaks running lengthwise, or transverse bands.

The beaded sea cucumber is found in the Caribbean Sea, the Bahamas, Jamaica, Cuba, the Gulf of Mexico, Mexico, Costa Rica, Panama, and the Lesser Antilles. It also occurs in the Canary Islands. It lives on reefs down to about 30 meters deep, hiding during the day among boulders and coral rubble.

It is a detritivore, using its tentacles to sift through seabed sediment and push it into its mouth. Organic material is digested, and the inorganic waste is expelled through the cloacal vent.

Movement happens through muscle contractions in the body wall, which includes both longitudinal bands and circular bands. Waves of peristalsis along the body allow it to crawl, with the ossicles providing grip on the substrate. In an aquarium, it can even climb vertical glass using this peristaltic motion, with only its tentacles providing attachment.