Star pearlfish
Star pearlfish (Carapus mourlani) is a slender, silvery fish in the Carapidae family. It normally lives inside a starfish or a sea cucumber, in the host’s body cavity, usually without hurting it. The fish grows up to about 17 cm long. It has a translucent, scaleless body with dark spots, and the dorsal and anal fins run along its length. It has no pelvic fins. The upper jaw has many small, pointy teeth arranged in rows, but there are no large fangs. The eyes are well developed, even though the fish spends most of its life in darkness. It has a two-chambered swim bladder located under the 9th and 10th vertebrae and 15–17 precaudal vertebrae.
Star pearlfish are found on reefs in the Indo-Pacific Ocean down to about 150 m (490 ft). Their range includes the coasts of South and East Africa, the Seychelles, India, Indonesia, the Philippines, Japan, Micronesia, northern Australia, and Hawaii.
They are commensals of starfishes such as Culcita novaeguineae and holothurians (sea cucumbers) such as Bohadschia argus and Stichopus species. They spend most of their time inside the host’s body cavity, coming out mainly at night to feed. They may eat small crustaceans, other pearlfish, and possibly polychaete worms.
Reproduction usually involves the fish living alone, or as a male–female pair. It can enter the host through the sea cucumber’s anus or, when living in a starfish, through grooves near the tube feet. A pair may release eggs inside the host, with fertilized eggs later entering the water.
A study looking for genetic differences between pearlfish living in holothurians and those living in starfish was inconclusive. In one experiment, a large sea cucumber released 14 pearlfish when placed in relatively cold water, with one more remaining inside, a possible record number for this group.
This page was last edited on 2 February 2026, at 09:45 (CET).