''Euapta lappa'', the beaded sea cucumber, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...

s in the family

Synaptidae Synaptidae is a family of sea cucumbers that have no tube feet, tentacle ampullae, retractor muscles, respiratory trees, or cuvierian tubules. They also lack radial canals of the water-vascular system, with only the circumoral ring present. S ...

in the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Echinodermata An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea li ...

. It is found on coral reefs in the Caribbean region.

Description

In appearance, the beaded sea cucumber resembles a long worm rather than a sea cucumber. It can reach up to a metre (yard) in length and has a diameter of up to . It lengthens and shortens repeatedly and when disturbed, the normally flaccid body retracts vigorously to a fraction of its original length. It has no internal respiratory tree, nor does it have

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

, and the body surface is covered by rounded ridges. The skeletal structure consists of many tiny calcareous plates embedded in the cuticle. Little hooks project from these ossicles and make the body feel sticky to the touch. At the anterior (front) of the animal there is a ring of fifteen branched feeding

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s. The body colour is pale brown or grey, often with white flecks or darker, longitudinal streaks and transverse banding.

Distribution and habitat

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 is also known from the Canary Islands. It is found on reefs at depths down to about , hiding during the day among boulders and coral debris.

Biology

The beaded sea cucumber is a

detritivore Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...

. It uses its tentacles to sift through sediment on the seabed, pushing it into its mouth aperture. The organic material in the sediment is digested and the inorganic matter is expelled through the

cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, a ...

l vent. Locomotion takes place as a result of contraction of

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

s in the body wall. These consist of both longitudinal bands of muscle and continuous circular bands forming a tube. The contraction of different regions of musculature enables the sea cucumber to move around as waves of

peristalsis Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, which ...

pass along the body. The ossicles prevent slipping by providing friction with the substrate. In an aquarium, this sea cucumber can climb the vertical glass side by using peristalsis in this way, with the only point of attachment being the tentacles.

References

External links

* {{Taxonbar, from=Q2490519 Synaptidae Animals described in 1850 Fauna of the Atlantic Ocean