Synapta maculata

Synapta maculata, also called the snake sea cucumber, belongs to the family Synaptidae. This species lives in shallow tropical waters across the Indo-Pacific region. Reaching up to 3 meters (10 feet) in length, it ranks among the longest sea cucumbers known.

Description

The body is long and slender, with fifteen tentacles, and typically grows to about 2 meters (7 feet). While not the heaviest or bulkiest, it is likely the longest, with exceptional individuals exceeding 3 meters (10 feet).

Its coloration varies, ranging from yellowish-brown with wide, dark longitudinal stripes and patches. The ossicles—microscopic, calcareous, spike-like structures supporting the body wall—are large and anchor-shaped, used for locomotion, and can reach 2 millimeters in length. These ossicles are adhesive, making the sea cucumber very hard to pull off a wetsuit.

Distribution and habitat

This species is native to the tropical western Indo-Pacific. It inhabits depths down to about 20 meters (66 feet) on reefs and soft seabed sediments among seagrasses and seaweeds, and can also bury itself under rubble.

Biology

The tentacles surround the mouth and are used for surface feeding. When extended, they are about 2.5 centimeters (1 inch) long, with a short stem and a feather-like blade bearing thirty to forty pairs of pinnules. The outer tentacle surfaces have numerous bulges and are adhesive; the inner surfaces are smooth, with clusters of cilia near the base. The tentacles move continuously, flattening against the substrate or seagrass leaves to collect food particles by adhesion.

They then bend inward until the tips reach the mouth, where the buccal sphincter muscle scrapes off the food. The entire process takes only seconds, and several tentacles can deliver food simultaneously. If disturbed, the tentacles retract into the pharynx but soon emerge again to gather more particles.

The outer tentacle surfaces contain many vesicular cells, and a few scattered vesicles also appear on the body surface. Their function is unclear, but they may contain a noxious substance for defense. Since tentacles are vulnerable to fish predation, a bad taste would allow the sea cucumber to spend more time feeding instead of constantly retracting its tentacles when fish approach.