Blue-ringed octopuses, including the genus Hapalochlaena, are four highly venomous species of octopus found in tidal pools and coral reefs in the Pacific and Indian Oceans, from Japan to Australia. They can be identified by their yellowish skin and distinctive blue and black rings, which change color abruptly when the animal is threatened. They feed on small crustaceans, including crabs, hermit crabs, shrimp, and other small marine animals.
Source: Animal Fact Files
Blue-ringed octopus: small, brilliant and especially deadly
Blue-ringed octopuses are undeniably gorgeous. When they are alerted, these animals will show off the iridescent blue rings of the same name that cover their bodies and arms.
But their astonishing diminutive size and viewable appearance are deceiving: blue-ringed octopuses are some of the ocean’s most venomous animals.
What is a blue-ringed octopus and where do you find it?
Blue-ringed octopuses are a group of highly venomous cephalopods.
These small octopuses have been found in the Pacific and Indian oceans. They usually live on coral reefs and rocky areas of the seafloor, although some species can be found in tidal pools, seagrasses and algae beds. They are usually nocturnal, emerging at night to hunt crustaceans and sometimes small fish.
As their name suggests, these octopuses have multiple blue rings on their body and arms. These rings are an example of pseudoscience, where animals use bright colors as a warning to impending predators.
But unlike other deadly animals like poison dart frogs or velvet ants, which often display their bright colors, blue-ringed octopuses only appear when they feel threatened.
Octopuses have thousands of pigment cells under their skin. These are specialized cells that allow them to change color instantaneously. Blue-ringed octopuses pose a threat using these cells and iridophores, a type of specialized light-reflecting cell that gives blue-ringed octopuses their metallic luster.
When alarmed or attacked, these animals quickly change color. They use muscles to make their blue motifs appear, displaying them against a yellow or cream background with dark pigment cells underneath the rings, helping to deepen their color.
Like many other species of octopus, blue-ringed octopuses can also use their pigment cells to camouflage themselves. They spend a lot of time hiding in crevices, hiding from animals that might try to eat them.
There may be around 10 different species of blue-ringed octopus, although only four have been scientifically named.
The larger blue-ringed octopus (Hapalochlaena lunulata) is about 12 cm long including its arms. This species prefers shallow areas, up to 20 meters deep. It has been found in the waters around Indonesia, the Philippines, Papua New Guinea, Vanuatu and the Solomon Islands.
Southern blue-ringed octopus (Hapalochlaena maculosa) is found at depths of up to 50 meters along the southern coast of Australia, including around Tasmania. It grows to about 22 cm long and its base can range from gray-green to cream, with 50-60 blue rings.
Despite its name, the blue-rimmed octopus (Hapalochlaena fasata) is also a member of the group. It has iridescent blue lines on its mantle (the muscular structure behind the octopus’s head, which houses all of its organs), but it also has distinctive blue rings on its arms. This species grows up to 15 cm long and is found in waters off eastern Australia, from southern Queensland to southern New South Wales at depths of up to 20 meters.
The fourth species, Hapalochlaena nierstraszi, has only been officially recorded twice: in the waters around the Andaman Islands in 1938 and in 2013 when one was caught in a trawl near Chennai, southeastern India. Little is known about this species, although the 1938 specimen had a mantle of 16 cm.
Blue-ringed octopus venom
The blue-rimmed octopus’s vibrant menacing displays aren’t just for show.
The symbiotic bacteria in the salivary glands of the blue-ringed octopus produce the toxin tetrodotoxin (TTX). This substance has a strong neurotoxic ability, blocking the transmission of nerve impulses. This prevents muscles from contracting and can have deadly consequences. Some reports say that TTX is more than 1,000 times more toxic than cyanide.
TTX is found in a wide variety of animals including fish, amphibians, and shellfish. Puffer fish is one of the famous examples. These fish are edible, but they sequester TTX in their internal organs, so if they are not prepared properly, they can cause deadly poisoning.
The blue-ringed octopus disperses TTX throughout its body. If they are eaten by other animals, TTX acts as a poison. There has been at least one case of human poisoning caused by someone mistakenly ingesting a blue-ringed octopus, although one study found that swallowing TTX could make it about 50 times less toxic than if it were given through. other means.
Blue-ringed octopuses can also inject TTX, delivering it as venom through a nearly painless bite.
Bites from blue-rimmed octopuses are quite rare, but these animals actually carry a lethal dose of TTX. There have been a handful of deadly encounters with these animals.
TTX can come into play quickly, rapidly weakening and paralyzing muscles along with a host of other potential side effects, such as vomiting and dizziness. Despite becoming increasingly unable to move, TTX victims often remain awake and aware until the lack of oxygen renders them unconscious. Death is usually due to respiratory failure, paralysis of the diaphragm. This can happen within minutes.
There is no antidote to TTX, and most care is supportive, such as ventilation to keep the patient breathing until the effects of the poison wear off.
Blue-ringed octopus endangered?
Experts don’t know how many blue-ringed octopuses there are, and it’s unclear if their populations are declining. Although no species are officially considered at risk, human activities can still affect them.
The blue-ringed octopus is a beautiful animal. They are traded internationally, but they probably won’t make good pets. © Sascha Janson / Shutterstock
One potential impact is on their primary habitat. Blue-rimmed octopuses are known to live in coral reefs, which are facing threats such as warming waters, ocean acidification and pollution, to name a few. Seagrass also declined similarly. The destruction of these habitats threatens the survival of the animals that depend on them.
Blue-rimmed octopuses are also traded internationally for keeping in aquariums. While some of their range is within Marine Protected Areas, these animals have been known to be harvested from the wild in areas where there may be few regulations regarding their collection. They also have a short lifespan, living for 2-3 years and are not expected to perform well in transit.
Arguably, the blue-ringed octopus is not a good pet. Like other octopuses, they are runaway artists, able to get themselves out of the safest tanks. This makes them a danger to curious children and well-wishers who may accidentally shovel them back into their tanks. This innocence is perhaps demonstrated by the many examples of people picking up wild blue-rimmed octopuses and showing them off on social media without knowing they were holding one of the most venomous creatures. Ocean.
Blue-rimmed octopuses are incredibly beautiful animals, especially when they display bright patterns. But despite their small size and beautiful color, it’s important to remember that their flashy rings are no mere threat. If you’re lucky enough to see one in the wild, you’re probably safe to see them from a respectful distance, but you should never pick one up.
