Thorny sea cucumbers (Colochirus quadrangularis) on the Shores of Singapore

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Phylum Echinodermata > Class Holothuroidea

Thorny sea cucumber
Colochirus quadrangularis
Family Cucumariidae
updated Feb 11

Where seen? This small colourful sea cucumber is sometimes commonly seen on our Northern shores. It appears to be seasonally abundant. There are times where many individuals are seen, jammed next to one another. At other times, few are seen, widely separated from one another.

Thorny sea cucumbers do not appear to burrow into the ground and are often found on the sand especially in seagrass areas, clinging to tubeworm tubes or other hard surfaces.

Features: 6-10cm long, and really tiny ones hardly bigger than a seagrass leaf are sometimes also seen. Body short, squarish or quadrangular in cross-section with a distinct upperside and underside. The underside has three rows of short red tube feet. The tube feet may be used to stick to seagrass or cling to hard surfaces. The upperside has soft, harmless thorn-shaped projections. The anus has five tiny teeth-like structures. Colours range from bright red or orange, with shades of grey and green or bluish lines along the length. The feeding tentacles may be yellow, orange or red.

Sometimes confused with the Pink warty sea cucumber (Cercodemas anceps) which looks similar and is found in the same habitat. The Pink warty sea cucumber is less common and has pink warty bumps instead of soft thorns.

What does it eat? It gathers plankton and suspended organic particles from the water with feathery feeding tentacles. Each tentacle is stuffed one by one into the mouth to wipe off any edible bits that are stuck to it.

Thorny friends: Sometimes, tiny transparent shrimps (Periclimenes sp.) are seen among the feeding tentacles or on the body.

Human uses: Thorny sea cucumbers are among the sea cucumbers harvested for the live aquarium trade, although not as popular as the more colourful Sea apple sea cucumber (Pseudocolochirus violaceus). Like other fish and creatures harvested from the wild, most die before they can reach the retailers. Without professional care, most die soon after they are sold. Often of starvation as owners are unable to provide the food that they need to survive. Those that do survive are unlikely to breed.

Status and threats: Although not listed among the threatened animals of Singapore, like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Over-collection by hobbyists can also have an impact on local populations.