Distribution:
Atlantic, Indian and Pacific oceans, some also occuring in brackish water or in streams in the tropical Pacific.
Habitat:
Cardinalfishes live over coral and rocky reefs as well as nearby sandy patches or seagrass beds, however certain species make themselves at home in more specialized locations. Members of the genus Diadema, for instance, find shelter among sea urchin spines while some members of the genus Acanthaster live alongside the crown-of-thorns starfish.
Remarks:
The apogonid cardinalfishes are small fishes, with ovate to elongate, moderately compressed bodies. They have large eyes (the diameter of which exceeds the snout length) and large mouths, often with protruding lower jaws. Most species are nocturnal, and species of the genus Siphamia have a ventral light organ.
Characteristic features of these fishes include the double-edged preopercle, which can be either serrated or smooth, and the two separate dorsal fins (the first bearing 6-8 spines, the second bearing 1 spine and 8-14 soft rays). While many other fishes have separate dorsal fins, the cardinalfishes are are unique because the distal radial of the last spine is short (not elongate).
The jaws on these fishes contain bands of small, villiform teeth. Teeth are present on the vomer but may be present or absent on the palatine. There are enlarged canines in the premaxilla of some species.
The scales are usually ctenoid, occasionally cyloid and are absent in members of the genus Gymnapogon. Color varies, but cardinalfishes are often shades of black, brown, yellow or red, often with a pattern of dark bars or stripes.
Many members of this family are mouth breeders, that is, they carry their brood in their mouths. It is suspected that in some species only the males incubate the eggs, however in others species, that duty is left solely to the females.
This family contains 23 genera and about 273 species. There are two subfamilies: Apogoninae and Pseudaminae.
References:
Allen, G.R. in Carpenter & Niem 1999;
Nelson 2006