White Spot Cucumber

Overview

The White Spot Cucumber (Holothuria poli) is a common sea cucumber frequently found in the Mediterranean Sea, the Red Sea, and parts of the eastern Atlantic Ocean. It is a sedentary, bottom-dwelling species often observed in shallow coastal waters, where it plays a role in processing marine sediments.

Distribution & habitat

This species is widely distributed across the Mediterranean, the Red Sea, and the eastern Atlantic, ranging from the Canary Islands to the Bay of Biscay. It typically inhabits shallow waters from the surface down to approximately 20–40 meters, though it has occasionally been recorded at greater depths. It favors mixed substrates, including sandy and rocky bottoms, and is particularly common in seagrass meadows such as Posidonia oceanica.

Appearance

Holothuria poli has a cylindrical, elongated body that can reach up to 25 cm in length. Its thick, leathery skin is typically a mottled brown or grey, often featuring blackish spots and numerous conical tubercles tipped with white. The animal possesses retractable tentacles around its mouth for feeding and rows of tube feet that secrete a sticky mucus. This mucus often causes sand, shell fragments, and organic debris to adhere to its body, providing effective camouflage that can make the animal difficult to distinguish from its surroundings.

Feeding

As a deposit feeder, this species is limnivorous. It uses its specialized oral tentacles to collect surface sediment, extracting organic particles for nutrition. After processing the material, it expels the cleaned sand in characteristic, cord-like strings.

Biology & behavior

This species is dioecious, meaning individuals are either male or female, though they lack obvious external sexual differences. During the breeding season, typically between November and January, individuals may adopt an "L" shape and rise from the seafloor to release gametes into the water column for external fertilization. Unlike some other sea cucumbers, H. poli lacks Cuvierian organs for defense.