PearlfishCarapidae

Pearlfish (Carapidae) are slender, scale-less bony fishes recognised by their elongated, often translucent bodies and small heads. Their dorsal fin rays are typically shorter than their anal fin rays, creating a tapering, eel-like form. 🌊 Red Sea species reach up to 30 cm (12 in) in length.

Adult pearlfish are typically nocturnal, living commensally or parasitically within the body cavities of invertebrate hosts, primarily sea cucumbers, but also large bivalves, gastropods, or starfish. They enter and exit the host's anus or siphon tail-first. Commensal forms feed on small crustaceans, while parasitic forms consume host gonads and internal tissues. Found from shallow reefs down to at least 200 m (660 ft) in sandy or rubble areas, their cryptic existence means they are rarely observed by divers. The common name "pearlfish" derives from some species being found inside the mantle cavities of bivalves, including pearl oysters.