Thelenota rubralineata

Thelenota rubralineata is a sea cucumber from the family Stichopodidae, within the phylum Echinodermata. It lives mainly in the central Indo-Pacific, on the seabed near coral. This species belongs to the genus Thelenota, whose members are large and possess a calcareous ring.

Description

Its body is elongated and roughly trapezoidal, measuring 30 to 39 cm long and 8 cm wide when not contracted. Like other Thelenota, it has a clear difference between its upper and lower surfaces. The dorsal side is covered with papillae and pedicels, while the ventral side has many podia scattered randomly. On the back, two rows of 13 to 15 large, conical arms stick out, many ending in spiked papillae.

The sides have a continuous row of multipapillate protrusions, with smaller outgrowths scattered elsewhere. The body is patterned with red lines over a white base; near the middle, these lines run parallel and cross to form maze-like designs. The conical protrusions share this pattern, with white-tipped papillae. The podia are pale greenish-yellow, and the twenty tentacles are red.

Distribution and habitat

This species occurs on outer coral reef slopes, among large rubble and coarse sand near islands, at depths of 20 meters and deeper. It is widespread across the Indo-Pacific.

Biology

Like other Thelenota, T. rubralineata has calcareous spicules—granules and branched rods—in its body wall, providing support and defense. Two polian vesicles aid locomotion. Five broad, V-shaped longitudinal muscles attach to the body wall. It also has a short digestive tract, two narrow respiratory trees, and a small circulatory system running alongside the intestines.

When moving, the lateral protuberances help it walk. If disturbed, it bends its body into a helix, bringing its mouth near its anus, and stays like that for up to 10 minutes or longer before moving again. Its lifespan is unknown, but like other echinoderms, it is thought to regenerate, so lifespan cannot be estimated but is assumed to exceed several decades in the wild.

Commercial uses

T. rubralineata and other echinoderms are commonly harvested in the Western Central Pacific, including Micronesia, Polynesia, Melanesia, Australia, and New Zealand. Divers have observed it to be widespread but rarely found in large numbers.