Octopus

Octopuses are characterized by their eight arms usually bearing suction cups. Most have almost entirely soft bodies with no internal skeleton. They have neither a protective outer shell nor any vestige of an internal shell or bones, like cuttlefish or squid.

Octopuses have a relatively short life expectancy, for as little as six months. Larger species, may live for up to five years under suitable circumstances. Reproduction is a main cause of death; males can only live for a few months after mating, and females die shortly after their eggs hatch. Endocrine secretions from the two optic glands are the cause of genetically-programmed death

Octopus blood contains the copper-rich protein hemocyanin, in cold conditions with low oxygen pressure, hemocyanin oxygen transportation is more efficient than hemoglobin oxygen transportation. The hemocyanin is dissolved in the plasmas instead of being bound in red blood cells and gives the blood a blue color.

Octopuses are highly intelligence, probably more intelligent than any other order of nvertebrates.Problem solving experiments have shown that they do have both short and long memory. Their short lifespans limit the amount they can ultimately learn. There has been much speculation to the effect that almost all octopus behaviors are independently learned rather than instinct-based, although this remains largely unproven. They learn almost no behaviors from their parents, with whom young octopuses have very little contact.

An octopus's primary defense is to hide, other defenses include the use of ink sacs, camouflage, and auto missing limbs. An octopus's camouflage is aided by certain specialized skin cells which can change the apparent color, opacity, and reflectiveness of the epidermis.

Octopuses have keen eye sight and have an excellent sense of touch. Jet propulsion is their fastest means of locomotion, followed by swimming and bipedal walking.

The north pacific giant octopus - ' Enteroctopus dofleini', is often cited as the largest octopus species. Adults usually weigh around 15 kg , with an arm span of up to 4.3 m. 0ne such record is of a specimen. weighing 272kg and having an arm span of 9 m .