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Octopus Facts
The octopus is found in every ocean in the world and there are approximately three hundred known species. They are known only to live in salt water and an octopus that lives in warm water is usually smaller than species that live in a cold water environment.
The octopus is a sub-species of mollusk, called a cephalopod. They belong to the same group as abalone, snails, limpets, chitons, oysters, scallops, mussels and clams.
An octopus's general defence is avoiding any conflict, however, they are a formidable opponent underwater with very strong arms and suckers, able to bite with their sharp beak and release ink to confuse any predator.
A bottom-dwelling animal, the octopus makes its home in holes and crevice's along the rocky shores of the ocean. During the day, an octopus spends most of its time hidden in its lair.
When it hunts, it propels itself by swimming or crawling along on its tentacles. Its large, lidded eyes are adapted to focus in dim underwater light.
When an octopus mates, the male sends waves of spermatophores down one of its arms - the hectocotylus's - into the female to fertilize her eggs. For about a week afterward, the female lays clusters of grapelike eggs inside her nest. She will not leave her nest in the month to six weeks that it takes to hatch.
 
The female cares for her eggs above, until they hatch! These images were captured in our tanks at the Bait House. Once hatched we release the babies into the ocean.
Because a female octopus does not eat while they are caring for their eggs, it is common for them to die of starvation. The eggs hatch into larvae that look like tiny versions of their parents. They come to rest on the seabed, where they mature quickly.
The octopus does most of its hunting at night. It emerges from its rocky lair to seek crabs, crayfish, and mollusks, which are its favourite foods. The octopus catches most of its prey by stealth. Having changed colour to blend in with its surroundings, the well-camouflaged octopus waits for prey to pass by and then seizes it with its long arms. The arms are powerful and flexible, with two rows of suckers that help it grip its slippery prey. The octopus then stuns its victim with a secretion of nerve poison. To stalk lobsters and other dangerous prey, the octopus squirts ink into the water to form a screen. Hiding behind the dark cloud, it creeps up on its victim and grabs it from behind.
If the octopus's prey is hard-shelled, the octopus punctures the shell by drilling with its tongue, which is covered in small, sharp teeth. The octopus's predators include moray and conger eels, dolphins and sharks. Whenever possible, the octopus will escape from its predators by shooting a jet of water through its body to create a burst of speed.
Often, however, the octopus avoids detection completely. It can change its body colour and texture so perfectly that it can virtually disappear. The colored pigment in its skin can be concentrated or diluted, forming stripes and patterns that blend into the environment. The octopus's ink sac also helps it avoid attack. It releases a disorienting black cloud that is accompanied by another secretion to dull the attacker's sense of smell.
An octopus can regenerate a lost arm and it is quite common to find octopuses missing arms in nature.
Another unique feature of the octopus is that it has three hearts! Each gill has its own heart to pump blood. Blood picks up oxygen in the gills, but after going through tiny capillaries, it loses its pressure. The third heart then pumps the oxygenated blood to tissues all over the body.
Octopi have excellent sight, smell and touch. Each of their suckers has sensors capable of identifying even the smallest of scents or hints of a food source.
Image by Ian Sipworth - www.ianskipworth.com
Octopus in New Zealand
Of the 42 species of octopus known from New Zealand, only a few are commonly encountered. Octopus live mainly on the sea floor. However, small specimens of the common octopus (Pinnoctopus cordiformis or wheke) and the fist-sized Octopus huttoni can often be found in tidal rock pools. As wheke grow, they venture into subtidal reefs. Reaching over 1 metre in length and 9 kilograms in weight, they are among the largest predators on the reef. They feed on crayfish, crabs and shellfish.
You can see an octopus closeup when you visit the Island Bay Marine Education Centre!
Giant Octopus
Two of the world’s largest species of octopus have been found around New Zealand:
• An incomplete specimen of the giant gelatinous octopus (Haliphron atlanticus), which grows to 4 metres in length and weighs 70 kilograms, was trawled from a depth of 920 metres near the Chatham Islands.
• The giant South Pacific octopus (Enteroctopus zealandicus), which reaches 3 metres and weighs 30 kilograms, has been identified from beaks found in the gut of beached whales.
KEY POINTS
• Length: Up to 4metres., but usually smaller.
• Weight: Up to 70kg. Females are mature at 1kg. Males, at 1.5kg.
BREEDING
• Sexual maturity: Females, 1 1/2 - 2 years. Males, earlier.
• No. of eggs laid: Up to 150,000.
• Hatching time: 4 - 6 weeks.
LIFESTYLE
• Habit: Solitary, bottom-dwelling.
• Diet: Mainly crabs, crayfish, and bivalves.
• Lifespan: Females usually die after breeding at about 2 years of age; males generally live longer.
RELATED SPECIES
• Octopi are closely related to squid, cuttlefish and nautiluses.
OTHER INTERESTING FACTS
• The first writing ink was made from pigment found in the octopus's sac.
• The octopus is messy. It is easy to identify its lair by the pile of discarded shells outside the entrance.
• If an octopus damages one of its vital arms, it can grow a new one.
• The octopus is capable of learning. In an experiment, octopi can be trained to distinguish between shapes and also able to recognize objects by touch.
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