Holothuria stellati

Holothuria stellati, commonly called the Brown sea cucumber, belongs to the family Holothuriidae. It was first described by Delle Chiaje in 1824. The species includes two accepted subspecies—Holothuria stellati dakarensis and Holothuria stellati mammata—but whether these should be considered distinct species remains under debate.

Description

This sea cucumber typically reaches up to 12.9 cm in length, rarely growing to 20 cm. Its body is cylindrical, colored light to dark brown with a few darker spots. The exterior is hard due to a calcareous endoskeleton. On the dorsal side, a rounded bivium bears two rows of large, pointed papillae.

The ventral side forms a flat trivium with three rows of podia that contain ossicles. These podia are used for both movement and feeding, as the animal pushes sand into its mouth. Compared to other species in its genus, H. stellati has smaller ossicles: tables range from 31 to 52 μm in diameter, spires from 21 to 42 μm tall, and buttons from 31 to 42 μm long. The mouth and anus are at opposite ends of the body.

Distribution

H. stellati inhabits both soft and rocky sandy substrates in tropical climates. It lives exclusively in the neritic zones of the benthos in the Mediterranean Sea and Adriatic Sea, near Western Italy, Monaco, Tunisia, Turkey, and Algeria. Unconfirmed reports also place it in the Canary Islands and Croatia.

Life cycle

The species has separate male and female sexes. Females release eggs into the water, where fertilization occurs externally. The larvae pass through two stages: first, a planktonic auricularia stage, then a barrel-shaped doliolaria stage before maturing into adults. Although some sea cucumbers can reproduce asexually by fission, no documented research indicates that H. stellati does so.

Diet

Little is known about its exact diet. It is an omnivore, feeding on plankton, algae, and floating detritus. Like other sea cucumbers, it engages in both suspension feeding and deposit feeding, sifting through large amounts of sediment or water and expelling waste through its anus.

H. stellati serves as host and prey to several copepod parasites, including Alantogynous dellamarei, Calpysina changeuxi, and Tisbe holothuriae.

The species is not well studied, and information on its population and distribution is limited. However, it is increasingly targeted by fisheries, especially in Algeria and Turkey.