Collared eel

The collared eel (Kaupichthys nuchalis) is an eel in the family Chlopsidae. It was described by James Erwin Böhlke in 1967. It is a tropical, marine eel known from coral reefs in the western Atlantic Ocean, including Texas, USA; the Bahamas, the Antilles, northern South America, the northwestern Gulf of Mexico, and the Caribbean. It is a benthic, solitary eel that primarily resides in tubular sponges. Males can reach a maximum total length of 16 cm.

The collared eel exhibits biofluorescence, that is, when illuminated by blue or ultraviolet light, it re-emits it as orange, and appears differently than under white light illumination. Biofluorescence may assist in intraspecific communication and camouflage.