Cuttlebone

Top and bottom view of a cuttlebone, the buoyancy organ and internal shell of a cuttlefish.
Cuttlebone of Sepia officinalis (left to right: ventral, dorsal, and lateral views). The cuttlebone is about 15cm in length.
Common cuttlefish Sepia officinalis
Tortoise with cuttlebone
Fossil cuttlebone of the Pliocene species Sepia rugulosa
Fossilised cuttlebone-like gladius of Trachyteuthis[1]

Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family Sepiidae, commonly known as cuttlefish, within the cephalopods. In other cephalopod families it is called a gladius.

Cuttlebone is composed primarily of aragonite. It is a chambered structure that the animal can fill with gas or liquid for buoyancy control. On the ventral (bottom) side of the cuttlebone is the highly modified siphuncle; this is the organ with which the cuttlebone is filled with gas or liquid.[2] The microscopic structure of cuttlebone consists of narrow layers connected by numerous upright pillars.

Depending on the species, cuttlebones implode at a depth of 200 to 600 metres (660 to 1,970 ft). Because of this limitation, most species of cuttlefish live on the seafloor in shallow water, usually on a continental shelf.[3]

When the cuttlefish dies, only the cuttlebone remains and will often wash up on a beach.

  1. ^ Fuchs, D.; Engeser, T.; Keupp, H. (2007). "Gladius shape variation in coleoid cephalopod Trachyteuthis from the upper Jurassic nusplingen and Solnhofen plattenkalks" (PDF). Acta Palaeontologica Polonica. 52 (3): 575–589.
  2. ^ Rexfort, A.; Mutterlose, J. (2006). "Stable isotope records from Sepia officinalis — a key to understanding the ecology of belemnites?". Earth and Planetary Science Letters. 247 (3–4): 212. Bibcode:2006E&PSL.247..212R. doi:10.1016/j.epsl.2006.04.025.
  3. ^ Norman, M.D. (2000). Cephalopods: A world guide. Conch Books.