Edible Sea Cucumber, Holothuria edulis
The Edible Sea Cucumber (Holothuria edulis) also known as the Pink and Black Sea Cucumber, is a species of echinoderm belonging to the family Holothuriidae. It was placed in the subgenus Halodeima by Pearson in the year 1914, making its full scientific name Holothuria (Halodeima) Edulis. It can be found in shallow water within the temperate and tropical western portion of the Indo-Pacific Ocean.
This species is of medium size and can grow to a length of about 12 inches. It has a roughly cylindrical shape with ends that are rounded but can retract and expand its body and adopt different shapes. It’s usually soft and pliable with smooth skin but, because of the special characteristics of its connective tissue, it can become firm and rigid. The body is lined with longitudinal rows of small tube feet which can be withdrawn into the wall of the body, leaving small hollows. About 20 tube feet are positioned in a ring around the mouth and are modified into feeding tentacles. This sea cucumber is typically a dark reddish brown color on the upper side and a pinkish mauve on the underside, but it has the potential to be grey or dark brown.
It is a common species in the western Indo-Pacific Ocean. It resides on the seabed at depths down to 66 feet. Its range stretches from the Red Sea and East African coast to Sri Lanka, China, Indonesia, Japan, the Philippines, and northern Australia. It’s found in numerous variations of habitats including sandy or muddy substrates, coral rubble and in seagrass meadows. It can be found in the inner or outer portion of the reef flats, on back reef slopes and in lagoons.
It’s predominantly nocturnal and has a tendency to hide during the day under rocks or pieces of coral. It’s a detritivore and it feeds by ingesting sand and debris which has gathered on the seabed which it picks up utilizing its feeding tentacles. Sand is pushed into the mouth and any organic matter that is present, including the biofilm around the grains, is digested as the sand passes through the gut. The indigestible matter is expelled from the anus, leaving a sand ridge as the animal moves around. During the feeding activities, the sea cucumber churns up the top few centimeters of seabed and ventilates the sediment.
The speed of movement for this species is very slow. It mostly moves by peristaltic action of the body wall, assisted to a restricted extent by the tube feet. It can anchor its feeding tentacles into the sand and haul itself along. If it gets overturned, it can use its feeding tentacles to help turn its body right side up.
It has separate sexes and spawns at any time of the year with gametes being liberated into the water column. The larvae are planktonic. This sea cucumber can also reproduce asexually by breaking into two parts, each of which can then regrow the missing organ.
As the name implies, Holothuria edulis is edible and it is dried and sold as “beche-de-mer” or “trepang” in Indonesia and China.
Image Caption: Pinkfish (Holothuria edulis), Pulau Aur, West Malaysia. Credit: Anders Poulsen/Wikipedia (CC BY-SA 3.0)