|Greater blue-ringed octopus|
The greater blue-ringed octopus is, despite its vernacular name, a small octopus whose size does not exceed 10 centimeters, arms included, for an average weight of 80 grams. Its common name comes from the relatively large size of its blue rings (7 to 8 millimeters in diameter), which are larger than those of other members of the genus and help to distinguish this type of octopus. The head is slightly flattened dorsoventrally and finished in a tip. Its eight arms are short.
The coloration of this octopus varies with the circumstances and the ambient environment, from yellow ocher to light brown through whitish (when inactive). The blue rings, which number around 60, are spread throughout the entire animal's coat. The rings are roughly circular and are based on a darker blotch than the background color of the coat. A black line, with thickness varying to increase contrast and visibility, borders the electric blue circles. The blue rings are an aposematic adornment to clearly show to all potential predators that the octopus is highly venomous. The octopus also has characteristic blue lines running through its eyes.
The greater blue-ringed octopus is widespread throughout the tropical and subtropical waters of the Indo-West Pacific, from Sri Lanka to the Philippines and from Australia to Papua New Guinea, the Solomon Islands and Vanuatu. The animal likes shallow waters with mixed seabed (such as rubble, reefs and sandy areas). As is true for all octopuses, it lives in a burrow and only comes out to search for food or a mate. The entrance of the shelter is littered with remains from meals (empty shells and crab shell and legs) and is easily identifiable.
The greater blue-ringed octopus is a benthic animal that has a solitary way of life. The breeding season varies according to geographical area. The female lays 60 to 100 eggs, which are kept under the female's arms during the incubation period, which lasts about a month. Newborns have a brief planktonic development passage before settling on the seabed.
The greater blue-ringed octopus is capable of inflicting a deadly bite to its predators that can even be fatal to humans. Octopuses from genus Hapalochlaena have two kinds of venom glands that impregnate their saliva. One is used to immobilize the hunted crustaceans before eating them. The second, tetrodotoxin, is used for defense and is found in several other sea creatures such as pufferfish. This toxin is a powerful neurotoxin with a strong paralyzing power. The bite is painless to humans but effects appear any time between 15-30 minutes and up to four hours, though the rate of onset of symptoms varies by individual, and children are more sensitive to the toxins.
The first phase of the poisoning is characterized by facial and extremity paresthesia, and the victim feels tingling and/or numbness on the face, tongue, lips and other body extremities. The victim may also suffer excessive sweating, severe headaches coupled with dizziness, speech problems, hypersalivation, moderate emesis, movement disorders, a feeling of weakness, cyanosis to extremities and lips and petechial hemorrhages on the body.
The second phase of poisoning usually occurs after eight hours and includes hypotension and generalized spastic muscle paralysis. Death may occur between 20 minutes and 24 hours after the onset of symptoms, usually resulting from respiratory paralysis. Throughout each of the phases of poisoning, the state of consciousness of the victim is unaffected.