Slender Pearlfish

The Slender Pearlfish (Encheliophis gracilis) derives its name from the Greek words "enchelys," meaning eel, and "ophis," meaning serpent. This species is a marine, reef-associated, and non-migratory fish, inhabiting depths ranging from 1 to 62 meters, and reaching a maximum length of 30 centimeters.

Considered uncommon, the Slender Pearlfish is a benthic species, commonly residing within starfish and certain species of sea cucumbers, specifically Holothuria scabra and Holothuria argus. Trott (1970) reported that within Holothuria argus, these fish often form male-female pairs and exhibit parasitic behavior. They primarily feed on the gonads and respiratory trees of their hosts and are frequently associated with Bohadschia argus.

Morphologically, the Slender Pearlfish is characterized by having 25 to 36 dorsal soft rays, 42 to 52 anal soft rays, and 136 to 140 vertebrae. The species displays an eel-like appearance with moderate to shallow body depth. Notable features include a nearly adnate maxilla, the presence of cardiform teeth, and branchiostegal membranes that are partially or completely united. The species lacks enlarged dentary or premaxillary fangs, a dentary diastema, pelvic fins, and a swim bladder rocker bone. Its swim bladder is long and tubular, extending significantly beyond the 12th vertebra.

Geographically, the Slender Pearlfish is found in the tropical waters of the Indo-West Pacific region.