Scuba divers who have sighted an octopus slipping and sliding discretely across the ocean floor or safely hiding within its surroundings are truly fortunate. An octopus is one of the most fascinating sightings for a diver.
Over 300 species of octopuses live in oceans and seas around the world. They have eight tentacles, no backbone, three hearts, and a large brain. They move through the water by jet propulsion via a funnel in their mantle, which acts like bellows. Octopuses release a concentrated blast of ink-like substance to raise a smokescreen for predators. Octopuses (like squid, cuttlefish, and nautiluses) are invertebrates, so they have no skeletons. They can squeeze their flexible bodies into narrow cracks, change color in a matter of seconds, and outwit predators with a clever disappearing act.
The octopus uses its tentacles for crawling and picking up things. Inside the octopus’ mouth is a large beak, made of the same substance as human fingernails. The octopus uses this to kill its prey. Adults feed on crabs, clams, snails, small fish, and even other octopi. They use sharp parrot-like beaks to crush the shells of their prey. Newly hatched octopuses are small enough to hide among plankton (algae), so their small food consists of copepods and larval crabs. Octopuses are also intelligent and have excellent eyesight. Their tentacles are very strong.
The well-known giant Pacific octopus can move more than 700 pounds. The Pacific giant octopus weighs up to 30 pounds and has a 12-foot tentacle span. Large octopuses are comfortable in deeper, cooler waters.
Octopuses are not typically aggressive. However, if you explore an octopus closeup while diving, use your hand to keep your regulator in your mouth! A whitish octopus indicates their fear, while red indicates their aggression. An aggressive octopus with a tentacle grip of the seabed and you at the same time presents a challenge that few divers can handle.
The male octopus has a special tentacle for mating. During reproduction, the male octopus takes this tentacle, puts it under the female’s skin, and passes to her over 4 billion sperm at a distance. The female stores the sperm in her mantle until she is ready to lay eggs, which takes about 11 months. It takes her a month to lay tens of thousands of eggs, which she guards for weeks. Brooding females continually squirt clean water on the eggs and use their suckers to keep them clean and free of disease. Octopus eggs hatch only after dark and are the size of a grain of rice. Hatchlings instinctively swim to the surface where they are mostly preyed upon by other creatures. Only a few hatchlings survive. After the babies are born, the mother dies quietly of exhaustion. The typical life span of an octopus is 4-5 years. Aging begins after the reproduction cycle.
Many deep ocean octopuses trace their origins to the waters around Antarctica. The migration began about 30 million years ago when the continent cooled and large ice sheets grew, forcing octopuses into ever deeper waters. The climate shift created a northbound flow of deep, cold water that carried the cephalopods to new habitats. As the octopus adapted to new niches, new species evolved. Deep water octopuses lost their defensive ink sacs, because the dark ocean depths required no camouflage screen.