Thornback Cowfish

Lactoria diaphana

The thornback cowfish (Lactoria diaphana) is a distinctive member of the boxfish family found across the Indo-Pacific region. Growing to about 25 cm, it has a rigid, boxy body encased in a carapace of fused bony plates, with two forward-pointing horns above the eyes and prominent spines along the back, giving it its common name. The body is typically pale with scattered dark spots or blotches. This slow-moving fish inhabits sandy and rubble areas near reefs, seagrass beds, and sheltered lagoons at moderate depths. It feeds on benthic invertebrates, algae, and small organisms found in the sediment. When threatened, cowfish can release a toxic mucus called ostracitoxin from their skin, which discourages predators. Their deliberate, hovering swimming style and curious nature make them approachable subjects for underwater photographers. Thornback cowfish are solitary or found in pairs, and their unusual silhouette makes them instantly recognizable even from a distance on the reef.