Tell me, O Octopus, I begs
Is those things arms, or is they legs?
I marvel at thee, Octopus;
If I were thou, I'd call me Us. 

- Ogden Nash

The marine environment is the home to some of the most marvellous creatures of the world. Being inaccessible to the world the marine life remains largely unexplored. But whatever part of it has been explored has revealed the beauty and mastery of nature. An octopus is one such wonder from the marine world. Characterised by eight legs, an octopus is classified under the family Octopodidae, order octopoda under phylum Mollusc.

An octopus is completely boneless. Though it belongs to the phylum mollusc yet it neither has an exterior shell nor any interior vestigial bone or shell. This enables them to squeeze through narrow gaps and slits while escaping from their enemy or hiding.

octopus hiding in a tube

Octopuses are very short lived organism with an average life expectancy of only six months. A few octopuses can survive for five years at most, under favourable conditions. Mating is one reason for most of octopus deaths. The male cannot survive or long after mating. While the females are genetically programmed to die after their eggs hatch. They have two optic glands that are activated once they lay eggs. These glands secrete endocrine hormones that result into their death.

Octopuses have three hearts; two are responsible to pump blood to the gills while the other one pumps blood to the rest of the body. Octopus’s blood is not red as other being. Their blood contains hemocyanin, a copper rich pigment which is bluish in colour. Under low temperature and oxygen concentration this pigment is more efficient than haemoglobin, the red oxygen carrying pigment found in most organisms.

Octopuses are one of the most intelligent beings on earth and they are undoubtedly the most intelligent invertebrates. They have a highly developed nervous system which is spread all over its body. 2/3rd of it nervous system is spread evenly in its arms and only 1/3rd is the actual brain. An octopus can easily be trained to recognise shapes, open a screw-cap container and use tools. In their natural habitats octopuses are known to make barricades from stones and use a mollusc shell or a coconut for protection.

The octopuses are masters of guerrilla and camouflage tactics of defence. An octopus can squeeze through tiny gaps and crevices to hide from its prey. They can also change colour adopting the colour of their surrounding anemones or corals to bluff.

An octopus can even eject ink to reduce visibility of the predator. This ink also diminishes the olfactory senses of the hunter.  In case of severe danger an octopus can detach its arms to distract the predator. A species of octopus the Mimic Octopus, use a blend of flexibility and camouflage to mimic more dangerous and poisonous animals such as eels, sea snakes or lionfish.

Mimic octopus

An octopus has highly developed vision and sense of touch. Some species can even detect colours. The suction cups in their arms not only serve to grip their prey, it has chemoreceptors that enable the octopus to taste everything that it touches.