Parastichopus regalis

The royal sea cucumber (Parastichopus regalis) is a member of the family Stichopodidae. It reaches about 20 cm (8 in) in length, with a soft, slightly flattened body. A distinct lateral fold lined with large papillae separates the mottled brown upper surface from the paler underside, which features a darker central streak. Its skin is reinforced by bony sclerites—including tables, terminal plates, and perforated plates—while the tentacles around the mouth contain elongated, branched, perforated, and arched rods.

This species lives in the Mediterranean Sea, along Africa’s eastern Atlantic coast, and in the tropical and subtropical western Atlantic, including the Gulf of Mexico. It prefers sand or other soft substrates, typically at depths between 100 and 300 m (300–1,000 ft), though it can occur down to about 800 m (2,600 ft).

The royal sea cucumber often hosts the pearlfish Carapus acus in a commensal relationship. The fish enters the cucumber’s respiratory tree through its anus, staying inside during the day and emerging at night to feed. Occasionally, two fish share a single host, and a pair may breed within it. When stressed, the cucumber can eject its internal organs and later regenerate them.

This sea cucumber is common and edible, consumed in parts of its range, but it is not deliberately fished—it is caught only as bycatch during deepwater trawling.