The ringed octopus, also known as the thaumoctopus Mimicus, is a fascinating and beautiful creature found in tropical reef environments. However, they have developed a fearsome reputation due to their potent venom which contains the powerful neurotoxin tetrodotoxin. This raises the question – just how dangerous are these small octopuses? Are ringed octopus poisonous and what effects does their venom have? Let’s take a closer look at the biology and behavior of these intriguing animals.
Description of the ringed octopus
The ringed octopus is a small species which grows up to 15 cm in length. They have characteristic white rings and eye-like spots on their brownish mantle which helps provide camouflage when they lurk in coral reefs. There are two main species – the greater ringed octopus (Thaumoctopus Mimicus) and the lesser ringed octopus (Thaumoctopus mimicus). Despite their small size, they have a powerful beak which can deliver a nasty nip. However, their main claim to notoriety is their highly toxic saliva.
Venom potency
The ringed octopus produces venom that contains tetrodotoxin, a neurotoxin that can cause paralysis and death at high doses. Tetrodotoxin blocks sodium channels, preventing nerve impulses and muscle contractions. This results in paralysis of the diaphragm and death due to respiratory failure. The LD50 (lethal dose for 50% of subjects) is only 8 micrograms per kg body weight if injected. This makes it over 1200 times more poisonous than cyanide. Therefore, ringed octopus venom is extremely potent and can be deadly even in tiny amounts.
Effects of envenomation
When a ringed octopus bites, the neurotoxic venom is transferred into the wound through its saliva. The effects depend on the amount injected but can include:
– Numbness and tingling around the bite site
– Difficulty swallowing and speaking
– Muscle weakness progressing to full body paralysis
– Respiratory failure
– Changes in blood pressure and heart rate
– Nausea and vomiting
– Blindness
– Coma and death in severe cases
Symptom onset is rapid, within 5-15 minutes after being bitten. Without medical treatment, paralysis and fatal respiratory failure can occur within hours. Supportive hospital care is essential to manage airway, breathing and circulation in severe envenomations.
Bite circumstances
Ringed octopuses are not aggressive animals. Most bites occur when people accidentally touch or step on one, provoking a defensive bite. Waders who tread on a camouflaged octopus are at highest risk. The small size of the octopus means bites often go unnoticed initially, delaying treatment. Bites usually occur on the limbs – hands, feet and legs. Severe, life-threatening envenomation is rare as only small amounts of venom are injected. Deaths are estimated at less than 10% of bites. Antivenom is not available.
Treatment
If bitten, immediately remove the octopus if still attached and immerse the affected limb in hot water to denature the venom proteins. Apply a pressure bandage and immobilize the limb. Seek urgent medical help. Supportive hospital care aims to:
– Maintain breathing – intubation and ventilation may be required
– Monitor heart rate and blood pressure
– Provide intravenous fluids
– Treat wounds and control infection
– Provide pain relief
With good supportive care, most victims will recover over 2-5 days as the venom is slowly metabolized and excreted. Extreme vigilance of airway and breathing is crucial in severe cases.
Prevention
To avoid being bitten when swimming or wading in coral reef environments:
– Wear protective footwear and/or waders in shallow water
– Watch carefully where you put your hands and feet
– Do not touch or handle any octopuses
– Leave any octopuses found undisturbed
– Educate yourself on basic first aid for bites
Conclusion
Ringed octopuses have an undeserved reputation as deadly killers. Although their venom is highly poisonous, most bites result only in mild symptoms due to the tiny amounts injected. Severe envenomations are rare and deaths are uncommon with proper medical care. Stings can be avoided by taking precautions not to touch or disturb these shy creatures when encountering them in reef environments. Despite the potency of their venom, ringed octopuses are fascinating animals that play an important role in the ecology of coral reefs and are not a major risk to humans.
References
| Sutherland, S.K. (1983). Octopus envenomation. Med. J. Aust. 144, 218-220. |
| Hwang D.F., Noguchi T. (2007). Tetrodotoxin Poisoning. Advances in Food and Nutrition Research, Vol 52. Academic Press. |
| Isbister G.K., White J. (2004). Clinical consequences of envenoming by far-eastern funnel-web spiders (Atrax species) in Australia. Toxicon. 43(2):133-8. |
| Williamson J.A., Fenner P.J., Burnett J.W., Rifkin J.F. (1996). Venomous and Poisonous Marine Animals: A Medical and Biological Handbook. UNSW Press. |
| Bingham J., Birchall M., Wickramasinghe N.T. (1979). Blue-ringed octopus bites in Australia. Med J Aust. 1(10):402-4. |
