Worm pearlfish

The worm pearlfish is typically 15 cm long and is characterized by its long, slender body and lack of scales.

E. vermicularis lives in a marine, reef-based environment in a tropical climate. They are an epibenthic species – they live near to the bottom of the seafloor. They seek out shallow-water sea cucumbers around in inshore waters and coral reefs which range in depth from 0-30 meters. They can be found in the Indo-Pacific, the Gulf of Aden, around the Philippines and Society Islands, and north to the Ryukyus to the eastern Pacific.

The worm pearlfish is a parasite of holothurians, each host is normally home to a pair of these fishes. Species recorded as hosting the worm pearlfish include Holothuria leucospilota, H. scabra, H. lubrica and Thelenota ananas. The worm pearlfish is an uncommon species. While other members of the family Carpidae can be commensal, most members of the genus Encheliophis are obligately parasitic. Worm pearlfish, specifically, prefer the coelomic cavity of the genus Holothuria (sea cucumbers). In particular, worm pearlfish have been found to prefer the sea cucumber species H. leucospilota, though they have been found in the sea cucumber species Holothuria atra as well. Worm pearlfish feed exclusively on the internal tissue of the host, entering through the anal region of the sea cucumber without causing the sea cucumber to release its Cuvierian tubules – a defense mechanism which entangles possible predators. The pearlfish appears to be chemotaxic (responsive to chemical gradients in water) and is attracted to chemicals the coelomic fluid and Cuvierian tubules, which leads it to the sea cucumber's anus. Because the other species worm pearlfish prey on, H. atra, lack Cuvierian tubules, worm pearlfish are most likely not only attracted by the Cuvierian tubules. …