Graeffe's Sea Cucumber

Overview

Graeffe's Sea Cucumber is a distinct, cylindrical echinoderm widely distributed across tropical Indo-Pacific coral reefs. It is easily recognized by its contrasting black feeding tentacles and unique appearance, which changes significantly as the animal matures.

Distribution & habitat

This species is found throughout the tropical Indo-Pacific, ranging from the east coast of Africa to the South Pacific, including the Philippines and Indonesia. It typically inhabits sandy substrates and rocky areas within coral reef environments, generally remaining in shallower waters.

Appearance

Adults are pale brown or cream-colored with prominent brown spots, black speckles, and small, thorn-like protuberances. They possess a ring of up to 25 paddle-shaped tentacles that are black on the upper side and white underneath. In contrast, juveniles are brightly colored in white, blue, or black with large yellow projections. This striking juvenile coloration serves as a form of Batesian mimicry, allowing them to resemble the toxic nudibranch Phyllidia varicosa to deter predators.

Biology & behavior

Graeffe's Sea Cucumber is a diurnal scavenger that remains active from dawn until shortly after sunset. During the night, it becomes immobile, often resting with its rear end raised and tentacles retracted. While it can eject sticky, toxic cuvierian tubules from its cloaca when under extreme stress, it is generally reluctant to do so. Growth is slow, and individuals may live for over a decade.

Feeding

This species feeds by sifting through seabed sediment with its specialized tentacles. It ingests organic matter, such as bacteria, micro-organisms, and decaying algae, while excreting cleaned sand back into the environment.