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 | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / Roberts, D. |
Taille de l’image : | 5165 px × 4416 px |
Model Release : | Non requis |
Property Release : | Non requis |
Restrictions : | - |