Bocas Species Database

Habitat: Seagrass beds of reef flats, and sand plains, from the fore reef to the back reef zone.   Distribution: Circumtropical   Natural History Notes: Large individuals may reside within dead conch shells or beneath coral rubble, but most individuals burrow several centimeters below the sediment surface. Burrowing produces a prominent conical mound at the surface of the sediment. But though abundant and visible, burrowed individuals are not easy to excavate, as they contract their bodies and wedge themselves tightly in their burrows. The species uses a feeding funnel terminating 15-20cm below the sediment surface to ingest nutrient-rich surface and sub-surface particles. Individuals feed at a constant intensity across a 24-hour cycle and change the position of the feeding funnel very little over a several month period. Up to 36 liters/ square meter per year of sediment may pass through the intestine of a single animal, suggesting that this species may play an important role in intensifying siltation. H. arenicola may be preyed upon by the trunk fish, Lactophrys trigonus. The rhabdocoel flatworm, Anoplodiera sp. has been observed in the animal's digestive tract.   Depth: Shoreline to at least 13 m   Characteristics: This holothuroid grows to a maximum length of 25 cm. Its mouth is located at the anterior end of its body, and is surrounded by 20 small tentacles. Small, cylindrical tube feet are scattered across the body, but are more dense on the lateral margins and the ventral surface. Toward the anterior and posterior ends, the tube feet are found on irregular warts, and the skin is stiff and rough. The body is slender, elongate, and tapered toward both ends. This species is tan, light brown, or pale gray, with contrasting flecks of darker brown, black, or rust color. Two longitudinal rows of 20 dusky blotches often run along the dorsal surface. Tentacles are yellowish, transparent and have a sprinkling of brown dots. Juveniles look significantly different from adults, but may be distinguished easily by their terminally placed mouth with yellow tentacles and by their tube feet with conspicuous yellow tips.