The Cardinalfishes family (Apogonidae) belongs to the order of Perciformes and can be found in tropical and subtropical waters of the Atlantic, Indian and Pacific Oceans. Although it is a predominantly marine family, there are 9 species of the genus Glossamine that live in freshwater in New Guinea and Australia.
Species of the Cardinalfishes family are characterized by very large eyes and a large mouth. Most species are nocturnal, remaining during the day hidden in cracks and caves. As a striking feature, the males of many of the species, are responsible for incubating the eggs, and this they do in the mouth. Therefore, once the clutch is laid, the male will stop feeding until his offspring have hatched. The diet of Cardinalfishes is varied, but mainly consists of zooplankton and small benthic invertebrates.
Cardinalfishes have a dorsal fin that is separated into two regions. The first region consists of 6-8 spines. The second dorsal fin has 1 spine followed by 8-14 soft rays. Both dorsal fins have a similar width, and the first dorsal fin is usually slightly lower in height than the second dorsal fin. The anal fin is formed by 2 spines followed by 8-18 soft spokes.
The maximum length of Cardinalfishes is 20 cm, although most species do not usually exceed 10 cm in length. A total of 347 species have been described, all of which are grouped into 33 different genera. The genus Siphamia is noteworthy, whose species has a luminous organ in the ventral region of the animal.