Cephalopods are a class of marine animals which include the octopus, cuttlefish and the squid.
The word cephalopod originates from Greek and literally translates to “head-feet”
These animals have a prominent head and a set of arms or tentacles. They are also able to produce and squirt ink. About 800 different species of cephalopods have been identified and range in size from 10mm (idiosepius thailandicus) to 14 meters (colossal squid) which is the largest living invertebrate.
Cuttlefish {Sepia officinalis} [Siċċa]
Cuttlefish are sometimes referred to as the "chameleons of the sea" because of their ability to rapidly alter their skin color in a fraction of a second. Cuttlefish change color and pattern (including the polarization of the reflected light waves), and the shape of the skin to communicate to other cuttlefish, to camouflage themselves, and to mimic other creatures to scare off potential predators.
Cuttlefish have sophisticated eyes
The cuttlefish pupil is a smoothly curving W-shape. They have two spots of concentrated sensor cells on their retinas (known as foveae), one to look more forward, and one to look more backward. The eye changes focus by shifting the position of the entire lens with respect to the retina, instead of reshaping the lens as in mammals. Unlike the vertebrate eye, no blind spot exists, because the optic nerve is positioned behind the retina. They are capable of using stereopsis, enabling them to discern depth/distance because their brain calculates the input from both eyes.
Although cuttlefish cannot see color, it can perceive the polarization of light, which enhances their perception of contrast
Both male and female cuttlefish die soon after mating
Head-to-head mating between male and female cuttlefish last on average 2.4 minutes per copulation. This is followed by an intermission of six or seven minutes while the female deposits her eggs into an overhang or crevice. This can happen up to more than a dozen times and on on average with two to eight different males per day. After the female lays her eggs, she never attends to the eggs again and keeps mating until she has exhausted her supplies of eggs and will head away and die soon after.
The males, once they have mated with all the energy they can muster and the last receptive female has left, will then wander off to a certain death.
The eggs develop on their own, if placed well, safe from predators, and they will gestate and develop for two to five months, ready, upon hatching, to hunt their prey and to mimic their surroundings to hide in plain sight.
White spotted octopus {Callistoctopus macropus} [Frajjel]
This night crawler will hunt by wrapping its mantle around a rock or coral and by searching all around the rock with its long arms
Other fish, such as groupers will stay close, waiting for any small fish that manages to get away from the octopus.
The octopus can create a water jet effect to travel faster
When it needs to get out of danger, the octopus can propel itself through water by creating a jet effect by squirting water at high pressure from its mantle cavity though a funnel. But since its three hearts and two gills are inside this mantle cavity, it cannot maintain this jet mechanism for very long as the high pressure created on these organs impairs its circulation and oxygenation.
An octopus can die from its own ink
Octopi squirt ink when they are faced danger and need to escape. This ink doesn’t just hide the animal but also physically harms the enemy. It contains an enzyme called tyrosinase which, when sprayed in a predator’s eyes, causes a blinding irritation and also messes up the sense of smell and taste. The defensive concoction is so potent, that octopi that do not escape their own ink cloud can die.
