Invertebrates are probably the strangest and most "alien" animals on the planet. Among them, one class of molluscs stands out for its extraordinary intelligence and complex specialisation: cephalopods, which include octopuses, squid, cuttlefish and nautiluses.

According to Sydney Brenner, a researcher at the Oist (Okinawa Institute of Science and Technology Graduate University), cephalopods "were the first intelligent animals on the planet". These animals have a highly developed nervous system and large brains; they are capable of solving complex problems and learn rapidly, and are able, among other things, to navigate mazes and open bottles and jars.

In addition to their incredible cognitive abilities, cephalopods are masters of the art of mimicry. They can alter their colouring by controlling cells called chromatophores. The colour change is instantaneous and allows these creatures to simulate sand or reef rocks, becoming virtually invisible.

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The cephalopods' "superpowers" serve both offensive and defensive functions. One particular species of cuttlefish (Sepia latimanus), for example, can produce light and dark bands across its skin that vary in intensity, creating a psychedelic effect that hypnotises its prey. Meanwhile, the mimic octopus (Thaumoctopus mimicus) can imitate the appearance and movements of over fifteen different creatures, mimicking venomous animals such as sea snakes and lionfish in order to protect itself.

From 8 to 12 October, these fascinating animals are celebrated during the World Cephalopod Awareness Days. The event was established in 2007 by members of Tonmo, The Octopus News Magazine Online forum, with the aim of highlighting the importance of protecting and deepening our knowledge of these mysterious creatures.

The days are divided as follows: 8 October is Octopus Day, dedicated to the most famous member of the family; 9 October celebrates the lesser-known cephalopods — it is Nautilus Night, honouring a true living fossil that first appeared in the Palaeozoic era; 10 October is Squid and Cuttlefish Day, dedicated to cephalopods distinguished by two tentacles in addition to their eight arms; 11 October is Kraken Day, celebrating the legendary creature that embodies the role these animals have played in the birth of sea monster myths; and finally, 12 October is Fossil Day, to commemorate all extinct cephalopods (scientists have identified approximately 17,000 extinct species through fossils, such as ammonites).

Currently, there are approximately 800 cephalopod species known to science, with many more still to be discovered. The future of these mysterious creatures is uncertain, however: fishing of these animals is steadily increasing, and they are threatened by climate change and the acoustic pollution produced by extractive activities.

No cephalopod is listed among the threatened species on the Iucn Red List, a testament to how little we know about these animals. In the ocean depths, unknown cephalopods may be hiding — ancient as time itself, undisputed rulers of a cold and dark world. That thought alone should be enough to make us look at cuttlefish and octopuses with different eyes and renewed respect.