Spirula shell. X-ray of the spiral internal shell of a ram's horn squid (Spirula spirula). Spirula is unusual among the cuttlefish in retaining inside

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Spirula shell. X-ray of the spiral internal shell of a ram's horn squid (Spirula spirula). Spirula is unusual among the cuttlefish in retaining inside its body an ancestral shell that related species have discarded during their evolution. The shell is thought to give the animal control over its buoyancy by varying the fluid to gas ratio in the shell chambers. Spirula is a carnivorous mollusc with a large, tentacled body. The ancestor of the cuttlefish and octopusses probably resembled the nautilus, having a spiral, chambered external shell.

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Size: 5165px × 4416px
Photo credit: © D. ROBERTS/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: -ra, -ray, animal, horn, invertebrates, mollusca, nature, rams, shell, spirula, squid, wildlife, xray, zoology