A slender cuttlefish of 11 cm (4.3 in) in the usual range and up to 21 cm (8 in) in large females, mottled brown with a pale line along the mantle edge and a hood-like fold over the head that gives it its name. It sits over sand near reef, holds position with a rippling fringe of fin, and is far easier to approach than a squid.
The cuttlebone is the interesting part. Inside the body sits a chalky plate divided into hundreds of thin chambers, and the animal controls its depth by pumping salt out of them so that water follows and gas fills the space, or reversing the process to sink. It is a buoyancy device of a kind no fish has, precise enough to let a cuttlefish hover motionless without a fin stroke, and strong enough to survive around 200 m (650 ft) of pressure before it implodes - which is what sets the depth limit of the species.
Hunting works at range. Two feeding tentacles, kept coiled in pockets under the eyes, shoot out and seize prey with clubbed tips, and the whole strike is over in well under a tenth of a second.
The species migrates inshore in season, and the females lay eggs in clusters attached to whatever holds still. It is fished commercially through much of the 🌊 Indian Ocean.
- a hood-like fold of skin over the head
- slender mottled brown body with a pale line along the mantle edge
- hovers motionless above sand on a rippling fin fringe
- usually about 11 cm, large females to 21 cm
