Holothuria grisea

The gray sea cucumber, Holothuria grisea, is a medium-sized coastal species that lives in the shallow, warm waters of the Atlantic. Its range stretches from Florida down to southern Brazil and across to West Africa.

Despite its common name, it is not typically gray; its color varies widely, from red to yellowish, often marked with brown patches. People harvest it for food, both locally and for export, with most of that fishing happening in Brazil. The species is not currently overfished and is not considered endangered or threatened.

Taxonomy

In terms of classification, Emil Selenka first described this sea cucumber in 1867. The genus name Holothuria comes from Latin for “water polyp.” It belongs to the phylum Echinodermata—Greek for “spiny skin”—which also includes sea stars and sea urchins. Within that phylum, it sits in the class Holothuroidea, the sea cucumbers. It is placed in the subgenus Halodeima and is also known by the synonyms Halodeima grisea and Ludwigothuria grisea.

Anatomy and morphology

Like all echinoderms, the gray sea cucumber has pentaradial symmetry. Its body is mostly cylindrical, with a flattened underside. Adults can reach up to 30 cm in length, but they average around 14 cm. The base color ranges from red to orange to yellow, with brown mottling that helps camouflage them among the reefs.

On the back, the papillae are white near the base and turn yellow toward the tips. The tentacles and the tube feet on the underside are also yellow. Tube feet, which echinoderms use for movement, work through hydraulic pressure. Adults have six rows of papillae on their dorsal surface, while juveniles have only four.

Each papilla holds 5 to 10 tube feet, and the mouth is ringed by 20 to 25 branched tentacles. The mouth faces downward because these animals are bottom feeders. Their bodies are reinforced by ossicles—calcified structures that form a kind of internal skeleton—and by internal plates. H. grisea is an osmoconformer, meaning its internal salt concentration matches that of the surrounding water.

Life history and reproduction

Reproduction in this species is gonochoristic, with separate males and females. Fertilization happens externally through broadcast spawning: eggs and sperm are released into the water column and must find each other. Spawning is seasonal, triggered by changes in light, temperature, salinity, moon phase, food availability, and other factors.