Molluscs
Common cuttlefish
Sepia officinalis
Epipelagic zone
A true chameleon of the sea, the common cuttlefish can change color and skin texture in a fraction of a second, thanks to thousands of pigment cells wired directly to its brain.
🗺️ Geographic range
Lives in the Northeast Atlantic and the Mediterranean Sea, ranging from Shetland and southern Norway down to Northwest Africa, on coastal sandy or muddy seabeds.
📊 Population
No global decline is documented; the species remains common and is widely fished commercially in the Northeast Atlantic and Mediterranean. Its very short life cycle (1–2 years) and high fecundity allow populations to rebound quickly even under fishing pressure.
Habitat
- Atlantic Ocean · High seas / open water · Epipelagic zone · Permanent
🥚 Reproduction
After mating, the female lays her eggs in black clusters ('sea grapes') attached to algae or submerged structures, and typically dies shortly afterward.
Behaviour
- Diet
- It hunts crustaceans, small fish, and mollusks, often mesmerizing prey with pulsing waves of color before seizing it with its two retractable tentacles.
- Hunting
- It uses active camouflage to blend into its surroundings, both to ambush prey and to evade predators.
- Communication
- Males use complex color patterns to intimidate rivals and court females, sometimes displaying two entirely different patterns on each side of the body at once.
- Social life
- Largely solitary outside the breeding season, when males and females gather to court and mate.
Physiology
- Anatomy
- It has three hearts and blue-green, copper-based blood (hemocyanin) instead of iron-based blood.
- Respiration
- Gill-based: water is pumped through the mantle cavity, which also propels the animal by jet.
- Vision
- Its eyes, with their distinctive W-shaped pupils, are colorblind but detect polarized light with an acuity unmatched in the animal kingdom.
- Adaptations
- Its internal porous bone, the cuttlebone, acts as an adjustable float by regulating the gas-to-liquid ratio inside it.
⚡ Its extraordinary abilities
- Changes skin color and texture in a fraction of a second using thousands of chromatophores individually controlled by the brain
- Detects polarized light with extreme sensitivity — a sensory ability humans entirely lack
🏆 Records
Most sensitive polarized-light vision in the animal kingdom
Cuttlefish species have shown the ability to detect polarized-light orientation changes of just one degree — a record among studied organisms.
If you cross paths with this animal…
Risk: Essentially no danger to humans; it is not considered significantly venomous, unlike its relative the flamboyant cuttlefish.
Behaviour: Rather shy, it favors fleeing or camouflage when approached by a diver, and only bites if handled and stressed.
Advice: Observe without touching, to avoid disrupting its camouflage or risking a small defensive beak bite.
💡 Did you know?
- The common cuttlefish typically lives only one to two years, an extremely short lifespan for such a behaviorally complex animal.
- It is colorblind yet still manages to match its surroundings' colors perfectly — a paradox still studied by scientists today.
