Monday, December 14, 2015

Blue-Ringed Octopi: Tiny Venomous Denizens of the Ocean

Blue-Ringed Octopus
Blue-ringed octopus
Courtesy of Elias Levy
Blue-ringed octopi are small creatures found in the Indian and Pacific Oceans. They inhabit shallow seawater, particularly in southern Australia. Unfortunately, their size and choice of home make it possible for humans to unwittingly step on them. This is a highly unfavorable situation, as blue-ringed octopi possess some of the most dangerous venom on Earth.

Female blue-ringed octopi give birth to roughly 50 eggs after breeding in late fall. They carry these eggs around in their tentacles until it is time for them to hatch. This typically takes between three and six months. These octopi begin their lives at about a fraction of an inch. They are only about seven inches when they reach adulthood. They eat crabs and certain mollusks once they are large enough to feed.

When a blue-ringed octopus hunts, it envenomates its prey before eating. It has several mechanisms for doing so. It can simply release its venom into the water and wait while its prey becomes paralyzed. It can bite its prey before eating. It may even capture the animal, stick it in a bubble of its own body and release the venom into the bubble.

Blue-ringed octopi have brownish to yellowish background color with vivid blue rings over their entire bodies. These rings become brighter when the octopi are threatened. However, they are typically not aggressive, which means most bites happen when humans accidentally disturb them. In that split second it takes to step on a blue-ringed octopus and have it bite, it is unlikely those blue rings will brighten with enough time to warn the victim.

The venom of blue-ringed octopi is a neurotoxin. It creates a range of symptoms, such as paralysis, paleness, nausea, diarrhea, vomiting, drooling, stomach pain and seizures. Untreated, it can lead to death through shutdown of body functions. The problem is that the bite itself is described as painless or nearly painless. This makes it difficult to tell there is a bite until the dire symptoms kick in. Therefore, if you are walking in the shallow pools of water in the Indian and Pacific Oceans and feel a slight pinch on your foot, look down, carefully. If you are leaving the beach and your lips start to tingle, let someone else drive and warn him that you may have been bitten.


MacConnell, Ashleigh, Hapalochlaena maculosa, retrieved 7/9/11,

Moore, Robert, The Biology of the Venom of Hapalochlaena Maculosa, retrieved 7/9/11

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