The octopus is one of the most amazing invertebrates. There are over 150 species of them, and their scientific name is Octopoda. Octopuses, squids, cuttlefish, and chamber nautiluses are a special group of mollusks that evolved 500 million years ago. The octopus’s evolution is amazing. They have three hearts, nine brains, and copper-based blue blood. Over time, octopuses might have lost their shells, but they have more amazing defense strategies like: flexibility, agility, intelligence, and camouflage. Using its ink and color, the octopus has been called the chameleon of the sea and can camouflage more quickly than any chameleon on the Earth. When frightened, they squirt a cloud of ink, change to the color white, and then jet propel away. If surprised, they may squirt ink that can numb their predators. Without shells, they have had to develop the ability to recognise and react to danger instantly. They also cannot see colors. Their pupil is a horizontal line, they view the world horizontally, and their eyes can turn 180°so they basically have eyes on the back of their heads. An octopus can fit in anything as big as its eye because they don’t have either an internal or external skeleton. An octopus can perform eight different activities independently, using each of its eight arms. If one arm is lost it can be regrown.
The blue-ringed octopus is beautiful, but at the same time very dangerous and deadly. Its venomous bite can kill a human within minutes.Most octopuses are small, no larger than one or two feet but the North Pacific octopus stretched out to its full length would be a circle of arms around fifteen feet across. The octopus brain is huge compared to the overall size of the animal, which isn’t too surprising, seeing that it’s just a head with arms attached to it. By opening the web between each arm, the octopus drifts down through the water like a parachute and will pump water through the opening in the mantle and out through its funnel to help move and breathe. Each eight of an octopus’s arms have up to 240 highly sensitive suction cups lined up in two rows for a total of 2000 suckers. Three opposing sets of muscles in each sucker disc allow it to bend, contract, or stretch at any time. They can also feel and taste, and can exert a powerful grip.
Researchers have done all sorts of tests on octopuses to try to gauge how smart they really are and how they feel and respond. Over time, laboratory octopuses have learned to run mazes, recognize objects by touch, and sometimes outsmart the scientists. For example, one octopus used to sneak out of its tank each night, crawl into nearby tanks to eat fish, and would return to its own tank before workers would arrive the next day. An octopus was once caught consuming its own arm and that’s thought to have been caused by stress. They will sometimes even break a limb to impress a mate. Octopuses may change color, posture, or spread their limbs to communicate, or just change their posture for an invitation to fight, but at the same time they’re both very solitary and shy. Color changes on an octopus aren’t only for defense, but can also reveal its feelings and mood. For example, when mating, a dizzying display of stripes and colors can show intense emotion.
In some places, populations of octopus have been overfished almost to the point of extinction. Although octopus are hunted for food, the population of octopus may suffer more from human activities like pulp and paper processing that may add chemicals to the ocean.
Octopus may hunt during the day , but mainly hunt at night. They find their prey by poking their arms into cracks and crevices, but the suckers don’t only grab the prey, they taste it as well and then it will inject a paralyzing liquid to soften the flesh. When an octopus spies a crab on the ocean floor, it opens its webs (the fold of skin between arms), creating a pouch. It closes around the prey like an umbrella and carries it back to its den in a sack of water. An octopus’s diet depends on its habitat.
Octopuses can be found in almost every ocean in the world and more specifically in coral reefs, deep ocean sea, and the ocean floor. When octopuses are not out hunting for food they live alone in a den under a ledge in a pile of rubber or inside a coral cave.
Octopuses may mate for several hours but researchers haven’t been able to stay underwater for long enough to see if they do or if the female mates with several males. When octopuses mate, the male pushes sperm packets called spermatophores through his third right arm. A spoon-shaped tip, called the hectocotylus, scoops the sperm into the female’s mantle opening from the roof of her cave. When done mating, the female returns to her den and may build a wall using stones to seal the entrance. She will attach strings of eggs to the ceiling of her cave until around 50,000 or more eggs are hanging like glass beads. She squirts water over her eggs with her funnel to keep them clean and to supply oxygen for the developing babies and she won’t leave the den to hunt and will even refuse handouts from a diver. She can lose half her weight and eventually die of starvation. If the mom dies before the babies hatch, they will probably perish, too. Crabs, sea stars, and small fishes will invade the nest and eat both the mom and the unhatched eggs. Although the eggs usually hatch at night, the predators are quick to discover the newborn octopuses. Most hatchlings are eaten in their first half-hour of freedom by hungry fish.Hatching time varies with the water temperature. In cold water it may take around six and a half months. Eggs of a tropical octopus usually hatch in less than six weeks. The common octopus hatches 65-80 chromatophores. This number will increase by the time it reaches adulthood to one to two million chromatophores.
Millions of octopus are harvested each year and sold in Japan. Most octopuses live up to one to two years; even the fairly larger ones only live up to two to three years and only few offspring will grow up to reproduce themselves. Luckily, the few that grow up become very fast. When baby octopuses emerge, they look like miniature adults. Tiny octopuses the size of a pinkie finger nail can already change color, squirt ink, and jet propel backwards.
Over all these 500 million years the octopus, the amazing invertebrate, has evolved amazingly.