Octopus
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Source: Allaboutnature.com
Unlike cuttlefish and squid, octopi have no internal shell,
nor do they possess catching tentacles or fins. They have a
soft body with only equal-size eight arms, which can grow to
a length of 5 meters. Each arm has two rows of suction cups.
If it loses an arm, it will eventually re-grow another arm.
It has blue blood. An octopus has an eye on each side of its
head and has very good eyesight. An octopus cannot hear. They
live on the ocean floor. There are over 100 different species
of octopi. The Giant Octopus is the biggest octopus. This huge
mollusk is up to 23 ft (7 m) from arm tip to arm tip, weighing
up to 400 pounds (182 kg). The smallest is the Californian octopus,
which is only 3/8 inch (1 cm) long. Among the invertebrates,
octopuses have the most complex brain, with long and short-term
memories, as do vertebrates. They learn to solve problems by
trial-and-error. Once the problem is solved, octopuses remember
and are able to solve it, and similar problems, repeatedly.
Octopuses’ sense of touch is acute in its suckers. The rim of
the cups is particularly sensitive. A blindfolded octopus can
differentiate between objects of various shapes and sizes as
well as a sighted octopus. Octopuses have highly complex eyes,
which compare to human visual acuity. Focusing is done by moving
the lens in and out rather than by changing its shape as the
human eye dose.
Octopi eat small crabs and scallops, plus some snails, fish,
turtles, crustaceans (like shrimp), and other octopi. They catch
prey with their arms, then kill it by biting it with their tough
beak, paralyzing the prey with a nerve poison, and softening
the flesh. They then suck out the flesh. Octopi hunt mostly
at night. Only the Australian Blue-ringed octopus has a poison
strong enough to kill a person.
Octopi live in dens, spaces under rocks, crevices on the sea
floor, or holes they dig under large rocks. Octopi pile rocks
to block the front of their den. The den protects them from
predators (like moray eels) and provides a place to lay eggs
and care for them (a mother octopus doesn't eat during the entire
1 to 2 months she is caring for her eggs). In order to escape
predators, octopi can squirt black ink into the water, allowing
the octopus to escape. Another defense that octopi have is changing
their skin color to blend into the background, camouflaging
themselves. The octopus swims by spewing water from its body,
a type of jet propulsion.
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