Holothuria edulis

Holothuria edulis, also called the edible sea cucumber or the pink and black sea cucumber, is an echinoderm belonging to the family Holothuriidae. In 1914, Pearson assigned it to the subgenus Halodeima, giving it the full scientific name Holothuria (Halodeima) edulis. This species lives in shallow waters throughout the tropical Indo-Pacific Ocean.

Description

This sea cucumber is medium-sized, growing to about 30 centimeters long. Its body is roughly cylindrical with rounded ends, but it can change shape by retracting or expanding. Normally soft and pliable with smooth skin, it can become firm and rigid due to the special properties of its connective tissue.

Small tube feet line the body in longitudinal rows and can be withdrawn into the body wall, leaving tiny hollows. Around the mouth, about twenty tube feet are modified into feeding tentacles. The upper side is usually dark reddish-black, while the underside is pinkish-mauve, though it can also appear grey or dark brown.

Distribution and habitat

Holothuria edulis is common and widespread across the Indo-Pacific. It lives on the seabed at depths up to 20 meters. Its range stretches from the Red Sea and East African coast to Sri Lanka, Japan, China, Indonesia, the Philippines, northern Australia, and various Pacific islands. It inhabits sandy or muddy substrates, coral rubble, and seagrass meadows, and can be found on inner and outer reef flats, back reef slopes, and in lagoons.

Biology

Primarily nocturnal, it hides under rocks or coral pieces during the day. As a detritivore, it feeds by using its feeding tentacles to pick up sand and debris from the seabed.

Sand is pushed into the mouth, and organic matter—including biofilm on the grains—is digested as the sand passes through the gut. Indigestible material is expelled from the anus, leaving a sand ridge as the animal moves. This feeding activity churns the top few centimeters of seabed and aerates the sediment.

Locomotion is very slow. It moves mainly through peristaltic action of its body wall, with limited help from its tube feet. It can also anchor its feeding tentacles into the sand and pull itself along. If overturned, it uses its feeding tentacles to right itself.

Holothuria edulis has separate sexes and spawns year-round, releasing gametes into the water column. The larvae are planktonic. It can also reproduce asexually by splitting into two parts, each regrowing missing organs.