The Barspot cardinalfish (Apogon retrosella) is a small, nocturnal reef fish commonly found in the tropical eastern Pacific, including rocky reefs and coral areas. It has a compact, laterally compressed body with large eyes adapted for low-light conditions. The fish is pale red overall, marked by a distinct dark spot near the base of the tail and faint vertical bars along the body, which give rise to its common name. During the day it shelters in crevices or among reef structure, emerging at night to feed on small crustaceans and plankton. Like other cardinalfishes, it exhibits mouth-brooding behaviour, with males carrying the fertilized eggs in their mouths until they hatch.