The Devil Fish – Octopus

Water covers about three quarters of the earth and is found in oceans, seas, lakes, streams, ponds, etc. All these bodies of water contain a great variety of flora and fauna. One of those animals that is most easily found in the oceans is the octopus. The octopus is commonly known as the devil fish as its external appearance is frightening enough to scare a human and other animals. The octopus belongs to the Mollusca phylum and Cephalopoda class. The order to which it belongs is Octopoda and its habitat is completely marine.

The octopus has two eyes and four pairs of arms and, like other cephalopods, its body is bilaterally symmetrical. It has a beak and the mouth is located in the central position of the arms. The exoskeleton is absent, so it can get into small cracks. The power of intelligence is very well developed and it is perhaps the most intelligent animal among all invertebrates. It inhabits wide regions of the oceans, but is found mainly among coral reefs. For their defense from enemies, they basically hide or expel an ink material or display a color changing activity called camouflage. All octopuses are generally poisonous, but only the small blue-ringed octopuses are harmful to humans and take them to heavenly abode. Currently about 300 species of octopus are known.

Octopuses are very clearly identified by their eight dangerous arms, each with suction cups. Their arms are very different from those found in other cephalopods such as squid and cuttlefish. They have completely soft bodies with no signs of exoskeleton like the shell found in Nautilus and cuttlefish. They have a beak-like structure similar to that of a parrot but very small in size and it is the only hard structure present on their bodies. Their soft bodies allow them to hide under small areas when attacked. They have a very short lifespan, but some species can live up to six months. The giant North Pacific octopus can live up to five years under certain conditions. Their life expectancy is basically affected by reproduction. The males live for only a few months after mating and die later and the females die as soon as the eggs hatch. The females show parental care towards their eggs and do not feed until they hatch, but starvation is not the cause of their death. The two optic glands secrete endocrine substances that are responsible for programmed cell death. It has been found that if these optic glands are surgically removed, the octopus survives for many months after breeding, and if it then starves to death, it may die of starvation.

There are three hearts on the octopuses. The two are responsible for pumping blood from the two gills and the third is responsible for pumping blood from the entire body. Your blood carries a copper-containing protein hemocyanin, which is the oxygen carrier and pigment of blood. Hemocyanin is a much more efficient oxygen carrier compared to the oxygen-carrying hemoglobin of vertebrates. Hemocyanin is found dissolved in plasma and is not transported within the red blood cells of vertebrates and gives the blood a blue color. Octopuses draw water from their mantle cavity and, like other mollusks, have finely divided, highly vascularized gills present on the external or internal surface of the body.

Octopuses are highly intelligent and this is a matter of debate among scientists. Experiments have shown that they have short-term and long-term memory as well. Although they have a very short lifespan, they do learn and so far it has not been shown whether the young have innate behaviors or not. They have a very complex nervous system. Two-thirds of the neurons are located in the arms, and the arms have remarkable powers of autotomy. The arms also show complex reflex actions. Laboratory experiments have shown that they learn to distinguish between shapes and sizes and also break through aquariums in search of food.

The defense mechanism of octopuses basically consists of hiding under any suitable place so as not to be detected by their predators. Another mechanism includes quick escape from predators and they also secrete ink fluids, display camouflage and break their arms which is also part of their defense mechanism. Most octopuses love to secrete an ink fluid into the water as part of defense from their enemies and this ink fluid forms a cloud and confuses the prey and the octopuses run away. This ink liquid consists of a chemical called melanin which is responsible for giving human skin and hair their color. The ink liquid reduces the efficiency of the predators’ sense of smell and gives the octopuses a chance to escape. The chromatophores present in the epidermal layer of the skin of octopuses contain red, yellow, orange and black pigments that make the coloration of the skin similar to that of the background and the animal is protected from enemies. The iridophores and leukophores are the reflective cells and are also responsible for the appearance of the warning coloration. They also break their arms when attacked and their broken arms regenerate later.

The act of reproduction in octopuses is very different. During the act of reproduction, the male uses his special arm designated as heterocotylus and transfers the spermatophores through it to the female’s mantle cavity. In some benthic octopuses, the third arm is the heterocotylus arm. The males usually die after a few months when they have mated. In some species, females store sperm until their eggs have matured. When the eggs have been fertilized, the females lay around 200,000 eggs and their number varies between species. The females generally attach the eggs in the form of long strings to any solid substrate. Females also show parental care. They protect their eggs from predators and also provide air currents to the eggs so they can get the right amount of oxygen. The mother octopuses do not hunt and do not feed until the eggs hatch and they become too weak at that point when the eggs hatch and can be easily killed by predators. The young larvae that hatch from the eggs move to the upper surface of the sea and feed on plankton like copepods. This timing is very critical as they can be easily killed by their enemies when they grow large enough to go back to the bottom and the cycle repeats.

The sense of vision is very limited in octopuses and they can easily distinguish the polarization of light. Color detection is variable between species. The two sensory organs in the brain called statocysts help the octopus detect the orientation of its body. The autonomic response keeps the pupil of the eye in a horizontal position. They have a very good sense of touch. The suckers present on the arms are generally the chemoreceptors that help the octopus taste the substance it is touching. The arms also contain strain sensors, so they act as receptors of their own, but their actual function needs more attention from researchers. They move by crawling or swimming. They creep slowly. Jet propulsion performed by them is their fastest mode of locomotion, which is followed by swimming and crawling. Octopuses were worshiped by ancient peoples. They are often eaten as food by humans from many cultures. The Japanese and Hawaiians are very fond of octopus as it forms a very important part of their diet. They are also used as pets by many people.

Nature has provided a series of special tactics for the octopus to enjoy its life comfortably in its habitat.