International Cephalopod Awareness Days are from October 8-12 of any year. So it’s an excellent time to celebrate “the most intelligent invertebrates in the world”.
Cephalopod are marine animals with bilateral body symmetry, a prominent head, and a set of arms or tentacles. They all have the ability to squirt ink to confuse predators like a smokescreen. They are regarded as the most intelligent of the invertebrates with well-developed senses and large brains. They are also the fastest marine invertebrates and can easily out-accelerate most fish by the use of jet-propulsion or water jet.
Squid are cephalopods with 8 arms and 2 tentacles. Their shells have been internalized as a gladius, which is a slender sword. Squid are cone or torpedo-shaped with two fins on either side of their heads. They propel themselves through the water using siphons.
Cuttlefish are another member of class cephalopoda – able to change color and texture in a flash – making them a deadly predator. They eat small mollusks, crabs, shrimp, fish, octopus, worms and other cuttlefish. They are restricted by water temperatures so in the years when the seas warm up, their range will increase. ‘Cuttle’ is a reference to their unique internal shell, the cuttlebone.
Nautiluses are much closer to the first cephalopods that appeared about 500 million years ago than the early modern cephalopods that appeared maybe 100 million years later. Nautiluses are the sole living cephalopods whose bony body structure is externalized as a shell. The animal can withdraw completely into its shell and close the opening with a leathery hood. Unlike the large complex brains of octopus, cuttlefish and squid, nautilus have a seemingly simple brain. They typically have more tentacles than other cephalopods – up to 90 – but they lack suckers. To swim, the nautilus draws water into and out of the living chamber with its siphon which uses jet propulsion.
The chambered nautilus can be found along the slopes of coral reefs of the tropical Indo-Pacific. It movers to deeper waters (600–2,000 feet deep) during the day to avoid predators. At night it ascends up to the coral reefs (300 feet deep) to hunt for prey.