Longhorn Cowfish

The longhorn cowfish, Lactoria cornuta, is a variety of boxfish from the family Ostraciidae, recognizable by its long horns that protrude from the front of its head, rather like those of a cow or bull. They are a resident of the Indo-Pacific region and can grow up to 20 inches long. While badly suited to the home aquarium, the cowfish is becoming increasingly popular as a pet.

Adults are reef fish, often solitary and territorial, live around sand or rubble bottom up to a depth of 50 m. They are omnivorous, feeding upon benthic algae, various microorganisms, and foraminiferans that it strains from sediments, sponges, polychaete worms from sand flats, mollusks, small crustaceans, and small fishes, able to feed on benthic invertebrates by blowing jets of water into the sandy substrate.

There is no known sexual dimorphism, so both male and female display a yellow to olive base color, which is decorated with white or bluish spots. Paired courtship just before or after sunset. Eggs and larvae are pelagic.

One distinction from other fish is the lack of a gill cover, which is replaced by a small slit or hole. The hexagonal plate-like scales of these fish are fused together into a solid, triangular, box-like carapace, from which the fins and tail protrude. Their unique method of swimming, called ostraciform swimming, causes them to look as if they are hovering. They have no pelvic skeleton, so they lack pelvic fins. They are such slow swimmers cowfish are easily caught by hand, making a grunting noise when captured. This is the most well-known cowfish species in the aquarium trade.