Holothuria pervicax

Holothuria pervicax, known as the stubborn sea cucumber, belongs to the genus Holothuria. It gets its common name from the fact that it cannot survive in captivity. In the wild, it typically hides under rocks on warm-water reefs. This sea cucumber is gray or brown, with red-brown papillae and white tube feet used for movement.

Its body is elongated, with an oral-aboral orientation, and can reach up to 30 centimeters in length. The skin is soft and somewhat bumpy. Around the mouth are thin, branched tentacles, and poorly formed spicules are scattered across the body. Telling it apart from its close relative Holothuria fusconierea is difficult; the main differences are spicule size and slight color variations.

Distribution

Aquariums have never successfully kept this species alive, leading to the belief that it is highly sensitive and requires very specific conditions. Distribution Holothuria pervicax is found in the Maldives, Australia, Cebu (Philippines), Cook Islands, Comoros, French Polynesia, Guam, Hawaii, the Indo-Pacific region, Indonesia, Johnston Atoll, Kenya, Marshall Islands, New Caledonia, Papua New Guinea, Réunion, Somalia, the Sulu Sea, Tanzania, the Cocos Islands, the Seychelles, the Western Indian Ocean, and the Western Pacific Ocean. It prefers habitats under rocks on reefs in warm waters, with temperatures between 24°C and 28.7°C. Individuals have separate sexes, each with one gonad. Fertilization and spawning occur externally.

Diet

The planktonic larvae (auricularia) transform over time into barrel-shaped larvae, which then become juvenile sea cucumbers. These sea cucumbers are suspension and deposit feeders, usually active at night. They use a conveyor-belt feeding method, ingesting the surface of the substrate and defecating on it. Ecology Holothuria pervicax has several defenses against predators.

Ecology

It can expel its guts and large amounts of Cuvierian tubules when disturbed. It also releases a toxin called holothurian, which can kill fish, small worms, and mollusks. The toxin may be expelled through the anus or the front of the body, causing rupture of the tentacles, pharynx, and part of the intestine—all of which can regenerate over time. Expulsion through the anus entangles prey, but the tubule is destroyed and takes weeks to regrow.