Blue-ringed octopus

The blue-ringed octopuses (genus Hapalochlaena) are three or four small octopus species that live in tide pools in the Pacific, in places from Japan to Australia.

Overview

There are four species of Hapalochlaena:

Greater Blue-ringed Octopus (Hapalochlaena lunulata)
Southern Blue-ringed Octopus or Lesser Blue-ringed Octopus (Hapalochlaena maculosa)
Blue-lined Octopus (Hapalochlaena fasciata)
?Hapalochlaena nierstraszi - described in 1938 from a single specimen from the Bay of Bengal; the validity of this taxon has been questioned.

An individual blue-ringed octopus tends to use its dermal chromatophore cells to camouflage itself until provoked, at which point it quickly changes color, becoming bright yellow with blue rings or lines. It hunts small crabs, but will bite an attacker, even a human, if provoked or stepped on.

Poison

The blue-ringed octopus is the size of a golf ball but its poison is powerful enough to kill 26 human adults in minutes. There is no known antidote.

The octopus produces the venom that contains maculotoxin, 5-hydroxytryptamine, hyaluronidase, tyramine, histamine, trytamine, octopamine, tauring, actylcholine, and dopamine.

Maculotoxin is a type of tetrodotoxin, which is a neurotoxin produced by bacteria. Tetrodotoxin, is found in Pufferfish and cone snails. It blocks sodium channels causing motor paralysis and sometimes respiratory arrest leading to cardiac arrest because of a lack of oxygen.

First aid treatment is pressure on the wound and rescue breathing. It is essential that if rescue breathing is required that it is continued until the victim begins to breathe, which may be some hours. Hospital treatment involves respiratory assistance until the toxin is washed out of the body. The symptoms can vary in severity, with children being the most at risk because of their small body size. The victim might be saved if artificial respiration starts before marked cyanosis and hypotension develops. If the victims live through the first 24 hours after the bite they generally go on to make a complete recovery. It is currently the most toxic known sea creature in the world.

The blue-ringed octopus is the first animal reported to actually produce a tetrodotoxin rather than depend on bacteria.

Feeding

Their diet typically consists of small crab, and shrimp, but they may also feed on fish if they can catch them. They pounce on their prey, bite them then use their beaks to tear off bits. They then suck out the flesh from the crustacean's exoskeleton. In lab conditions they have been seen to eat each other although this has not been observed in the wild.

Mating

A male mates with a female by grabbing her mantle, then transferring sperm packets by inserting his hectocotylus into her mantle cavity over and over again. Mating continues until the female has had enough, and in at least one species has to remove the over-enthusiastic male by force. Males will attempt copulation with members of their own species regardless of sex or size, however interactions between males are most often shorter in duration and end with the mounting octopus withdrawing the hectocotylus without packet insertion or struggle.

Blue-ringed octopus females lay only one clutch of about fifty eggs in their lifetime towards the end of autumn. Eggs are laid then incubated underneath the females arms for approximately six months, and during this process she will not eat. After the eggs hatch the female dies, and the new offspring will reach maturity and be able to mate by the next year.