A swimming cube. The body is a rigid shell of fused hexagonal plates with holes cut for the eyes, mouth, fins and tail, so nothing about the fish bends: it moves by sculling with small fins while the body stays perfectly still.
The fish here is not the fish in the books. Across most of its range a yellow boxfish is yellow only as a juvenile, and adults fade to olive-brown with pale-centered spots as they grow. The 🌊 Red Sea population does not do that: it keeps the yellow into adulthood, so a large yellow boxfish, which would be a strange sight in the Pacific, is the normal thing on this coast. Populations of one species can diverge in appearance this way when a basin has been isolated as often as this one has.
The armor is the trade. It cannot flex, cannot accelerate and cannot hide, and in exchange it is very hard to bite and nearly impossible to swallow. Boxfish spend their days hovering in the open where other fish of their size would not last an hour.
The backup is chemical. Stressed or dying, the skin releases ostracitoxin, a soapy compound that damages the gills of other fish and can kill everything in a confined volume. In open water it does nothing to a diver.
Feeding is done by blowing: a jet of water at the sand to uncover worms and small crustaceans, then picking them off.
The species. Ostracion cubicum Linnaeus 1758 - cubic. ETYFish
- a swimming cube of fused hexagonal plates, with holes for the eyes, mouth, fins and tail
- here, yellow with dark spots at every age, unlike populations elsewhere
- juveniles bright yellow dice a couple of centimeters across
- hovers and sculls, body perfectly rigid
- up to 45 cm
