Noble sea cucumber

Holothuria princeps, called the noble sea cucumber, is an echinoderm from the family Holothuriidae. Like most of the roughly 1,100 sea cucumber species, it lacks obvious feet, eyes, mouth, anus, sexual organs, or appendages. Its body is cucumber-shaped, reaching about 30 cm long, and is covered in leathery, densely warty skin—the warts are mostly papillae. The coloration is brown, varying in shade, intensity, and pattern.

Distinguishing features include a thick, rigid body wall due to numerous grain-like calcareous ossicles. On the upper side, papillae of different sizes mix with tube feet that look similar and are used for movement and gripping the substrate.

The lower surface has tube feet arranged in about three series of six rows, more numerous in the middle. The mouth is a small, simple hole on the lower side near the front, ringed by 20 short, white, flat-topped tentacles only slightly larger than nearby papillae. Many sea cucumbers defend themselves by ejecting Cuvierian tubules from the anus, but this has not been observed in H. princeps.

Distribution

The species ranges from the U.S. coast of North Carolina and the Bahamas, south through the Caribbean (including Mexico, Colombia, and Venezuela), and along the Brazilian Atlantic coast. It burrows into sandy mud and shell substrates, and occurs in seagrass at depths down to about 73 m. In Brazil, it has also been reported from coral reefs.

Ecology

Like other holothurians, H. princeps is a large-scale detritus feeder, playing a key ecological role by moving and recycling up to 90% of the biomass in the ocean’s benthic zone. Its larvae develop in seawater, then metamorphose and settle on the seafloor to grow into adults.

Physiology

Sea cucumbers can regenerate damaged or lost parts. In one species (Leptosynapta), a small disk of tissue containing the mouth, a calcareous ring, and a nerve ring can regrow the entire animal. Another holothurian, after evisceration, has been observed to fully regenerate its digestive tube, hemal system, and respiratory trees (water lungs that pump water in and out through the anus for gas exchange).

Taxonomy

Emil Selenka first formally described Holothuria princeps in 1867, based on a collection from Florida, USA. The name sometimes appears as a synonym for the same species published in the same year—likely because Selenka also used it in his 1867 dissertation at the University of Göttingen.