Blue ringed octopus are four highly venomous octopus that are found in tide pools and coral reefs in the Pacific and Indian oceans, from Japan to Australia. They comprise the genus Hapalochlaena and can be by their yellowish skin and characteristic blue and black rings that change color dramatically when they are threatened.
These cephalopods are small, but are in fact one of the world’s most venomous marine animals. A single bite might lead to partial or complete paralysis, blindness, loss of senses, nausea, and resultant death within minutes, if left untreated. No blue-ringed octopus anti-venom has yet been discovered.
The blue ringed octopus is not thought to be of conservation concern currently, but the exact population number of these animals is unknown. They are threatened mostly by humans, with loss of habitat and overfishing.
Blue-Ringed Octopus Taxonomy
There are four confirmed species of Hapalochlaena, and six possible but still undescribed species being researched. The four species are:
- Greater blue-ringed octopus (Hapalochlaena lunulata): Found in the tropical waters of the Pacific Ocean
- Southern blue ringed octopus or lesser blue-ringed octopus (Hapalochlaena maculosa): Found along the southern coast of Australia
- Blue-lined octopus (Hapalochlaena fasciata): Found between southern Queensland and southern New South Wales, particularly in rocky shores and coastal waters at a depth of 15 meters (49 feet)
- Hapalochlaena nierstraszi was documented and described in 1938 from a single specimen found in the Bay of Bengal.
Blue Ringed Octopus Characteristics
Blue-ring octopuses are very small animals, measuring from 12 to 20 cm (5 to 8 in) and weighing 10 to 100 grams, depending on the subspecies and age. This makes them about the same size as a golf ball.
They are bilaterally symmetrical and have a notable appearance, with 50 to 60 bright blue rings along the dorsal and the lateral surfaces of the mantle. The base color of their mantle is yellowish, but can change to brighter shades when the octopus is threatened.
Like other octopuses, the blue-ringed octopuses have two very well developed eyes and two, strong parrot-like beaks.
Blue Ringed Octopus Lifespan
The blue ringed octopus has a fairly short lifespan of about two years. Male blue-ringed octopus can have an even shorter lifespan than this, as they die after mating.
Blue-Ringed Octopus Diet
The blue ringed octopus feeds on crustaceans, such as crabs and shrimps, and other invertebrates. They will also take advantage of small fish, especially injured ones, if they can catch them.
To catch prey, the blue-ringed octopus pounces on it, seizing it with its tentacles and bringing it towards the mouth. It then uses its horny beak to pierce through the tough exoskeleton of the prey and releases venom. The venom paralyzes the muscles required for movement, in turn killing the prey.
Blue-Ringed Octopus Behavior
Blue-ringed octopuses spend most of their time hiding in crevices. Like all other octopus, they can change shape easily, which helps them to squeeze into crevices much smaller than themselves. If they are provoked, they can change their color very quickly. They can become bright yellow and each of their 50 to 60 rings flashes bright blue as a warning display. These flashes are achieved by using muscles which are under neural control. Generally, the rings are not visible, or are very faint, when the octopus is as rest.
Although the blue ringed octopus is very small, it is very deadly. It carries enough venom to kill 26 adult humans within minutes. The toxin of these octopuses is created by a bacteria present in their salivary glands. Their bites are often painless, and victims may not know they have been bitten until symptoms start to show.
The major neurotoxin component of the blue ringed octopus bite is a compound that was originally known as maculotoxin but was later found to be identical to tetrodotoxin.
The venom can result in nausea, respiratory arrest, heart failure, severe and sometimes total paralysis, blindness, and can lead to death within minutes if not treated. Death is usually from suffocation due to paralysis of the diaphragm.
Despite their powerful venom, the blue-ringed octopus is not actually an aggressive animal. The first instinct of this octopus when cornered is to flee. If the threat persists, the octopus will then change its colors. If touched, the octopus will then use its venom.
The blue-ringed octopus flattens out its body on the bed for hiding from its enemies. It will also change its body color in order to blend into its surroundings.
Blue-Ringed Octopus Reproduction
The blue-ringed octopus begins mating when the male approaches a female and begins to caress her with his modified arm, the hectocotylus. The male then grabs the female, often completely obscures the female’s vision, and transfers sperm packets by inserting his hectocotylus into her mantle cavity repeatedly. Mating continues until the female has had enough, and in at least one species the female has to remove the over-enthusiastic male by force.
Female blue ringed octopuses lay only one clutch of about 50 to 100 eggs in their lifetimes. This usually stems place towards the end of fall. The eggs are then incubated underneath the female’s arms for about six months, and during this process she does not eat. As soon as the eggs hatch, the female dies because she has not eaten.
The hatchlings are tiny, about the size of a pea, but grow very quickly. By the time they are a month old they are able to hunt for food, and, by the time they are a year old, the new offspring reach maturity and are able to mate.
Male blue-ringed octopus displays homosexual behavior attempting to copulate with both the males and the females, and of all sizes. However, interactions between the males are most often shorter that ends with the mounting octopus withdrawing its modified arm without struggle or packet insertion.
Blue-Ringed Octopus Location and Habitat
The blue-ringed octopus can be found in the Pacific and Indian oceans, from Japan to Australia. These octopuses reside in tide pools and coral reefs and are bottom dwellers, inhabiting sandy and silty areas, and will even live inside empty sea shells, discarded bottles, and cans. They can usually be found at depths between 0 to 20 meters (or sometimes 50 meters). The blue-ringed octopus will come out of its shelter only to hunt for food or to search for a mate.
Blue Ringed Octopus Conservation Status
Blue-ringed octopuses are not endangered, and have not been listed on the IUCN Red List. Despite this, it is thought that these animals are threatened, mostly by humans. Rising sea temperatures and habitat loss is a big concern for the population of the blue-ringed octopus, as is over fishing. Blue-ringed octopuses are also commonly captured for aquarium display.
These animals are important to their ecosystem because they help control populations of Asian date mussels. Additionally, future research of tetrodotoxins produced by the blue-ringed octopus may produce new medicinal discoveries.
The blue ringed octopus is not hunted for its meat. In fact, the soft tissues of this octopus are extremely poisonous if consumed.
Blue-Ringed Octopus Predators
The biggest predator of the blue-ringed octopus is the moray eel. Other predators also include whales, seals, and different types of shore and marine birds.
Blue Ringed Octopus Fun Fact
The octopus’s own sodium channels are adapted to be resistant to tetrodotoxin, so they are immune to their own venom!
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