Holothuria impatiens

The impatient sea cucumber, also known as the bottleneck sea cucumber, belongs to the genus Holothuria and the subgenus Thymiosycia. Its body is long and cylindrical, reaching about 15 centimeters in length. The leathery skin is mottled brown, grey, or purplish-brown, often with alternating light and dark bands. Low, rounded papillae cover the surface, giving it a rough texture—a key feature that sets it apart from the similar Holothuria hilla.

Some papillae have concentric brown rings around them. Inside the skin are bony ossicles shaped like smooth buttons and square tables. At the thinner, front end sits a crown of about twenty tentacles, and this end may be darker than the rear.

This sea cucumber has an exceptionally broad range, spanning the tropical Indo-Pacific, the tropical western Atlantic, the Caribbean Sea, the Gulf of Mexico, the Mediterranean Sea, and the coasts of France. It lives on reef flats, in lagoons, or in open areas, typically under rocks or coral rubble, at depths from about 2 meters down to 40 meters.

Its common name likely comes from its habit of quickly shooting out sticky cuvierian tubules—enlarged parts of the respiratory tree that float in the body cavity—when disturbed, a defense that distracts predators. Nocturnal and secretive, it prefers small crevices. Once it finds a suitable crack, it relaxes its longitudinal muscles to squeeze in, then stiffens its collagen fibers to lock itself in place. While feeding, it only half-emerges.

As a deposit feeder, it sifts through sediment with its tentacles, ingesting dead organic matter like seaweed fragments. On the Great Barrier Reef, reproduction happens once a year in late spring or early summer. Females produce a small number of large eggs. Though some related species also reproduce asexually by transverse fission, H. impatiens has never been observed doing so.