Yes, all octopuses are venomous. They store venomous proteins in venom glands which they use to paralyze their targets when hunting. The deadliest and most venomous octopus is the blue-ringed octopus.
Although octopuses might look menacing, some would be surprised to hear they are vicious predators. They prey and pounce on defenseless small animals and kill them without mercy. But apart from their eight arms and sharp beak, there is one other thing helping them.
Not long ago, we, mankind, learned that octopuses are venomous. But how does their venom works? How potent is their venom? And are octopuses dangerous to humans?
This article covers everything you need to know about octopuses’ venom, including their toxicity, where it is stored, and how they use it.
Are Octopuses Venomous?
All octopuses are venomous. Their venom is stored and produced in venom glands. The potency of octopus venom ranges greatly between species.
A study in 2009 in the Journal of Molecular Evolution demonstrated that all octopuses are venomous to some extent.
Octopuses produce neurotoxins in their venom glands. They use it for hunting or self-defense.
They rarely attack humans and normally don’t fight back unless they are threatened. Most species do not have strong enough poison to harm us.[1]
How Does Octopus Venom Work?
The venom of the octopus contains neurotoxins that paralyze its targets upon injection. They inject their venom by biting. The venom is stored and produced in various glands in their bodies.
Octopus venom is different from snake venom. While potent snake venom causes paralyzation, blood clotting, and excessive tissue damage, octopus venom only causes paralyzation.[2]
Paralyzation can be deadly though. A potent neurotoxin can shut down the lungs, leading to death by respiratory failure.
Where Is the Octopus Venom Stored?
Octopuses store their venom in the venom glands. The most important venom glands are the salivary glands near their beaks.
What Does Octopus Venom Contain?
Octopus venom contains neurotoxins, most notably tetrodotoxin. This potent neurotoxin is also found in pufferfishes, toadfishes, and globefishes.[3] It also contains various organic chemicals and compounds, like dopamine and histamine.[4]
All octopus species have different mixtures of neurotoxins and organic chemicals in their venom.
How Do Octopuses Inject the Venom?
Octopuses inject their venom via their mouths. They have beaks and drill-like tongues designed to break the shells of crustaceans and mollusks. They transmit their venom by their saliva into the bite wounds.
Smaller octopuses do not bite but inject their venom into the eyes of their target. The venom can penetrate the skin as well without the octopus biting it, given prolonged contact.[5]
How Does the Octopus Venom Kill?
Octopus venom directly attacks the nervous system to shut it down. Tetrodotoxin interferes with transmission between nerves and muscles, stopping impulses. This causes paralysis all over the body.
The most vital muscles are the lung, heart, and diaphragm muscles. Once the tetrodotoxin affects these organs, death can occur in many ways:
- Respiratory arrest
- Heart failure
- Suffocation
- Cerebral hypoxia
The most potent octopus venoms can kill within a few minutes.[6]
Why Do Octopuses Need Venom?
Octopuses need venom for self-defense and to hunt. They use venom as a last resort for self-defense, as they prefer to swim away instead. Octopuses inject venom by biting into the eyeballs while hunting.
Octopuses are gentle and passive creatures. They rarely get aggressive and even rarer use their venom.
The only two scenarios when octopuses opt for venom usage are the following:
- Hunting
- Self-defense
1. Hunting
As octopuses hunt smaller creatures than themselves, they do not rely on venom to hunt. Big octopuses (like the giant Pacific octopus) can easily break through the shell of crabs.
Smaller octopuses might struggle with their prey while hunting. If struggling, they use their venom which they inject by biting.
The smallest octopuses that aren’t strong enough to break their target’s shell release their saliva into their prey’s eye.
Octopus venom isn’t only used to kill. Most octopuses are only toxic enough to paralyze smaller fishes, but not kill them.
Octopus beaks and tongues specialize in breaking down shells. Their venom is mostly an inconvenience to humans, but it can be deadly for their small targets.
Their diet includes the following animals:[6]
- Crabs
- Lobsters
- Snails
- Clams
- Small fishes
2. Self-Defense
Octopuses’ first form of self-defense is fleeing. They use their venom as their last line of defense. If a predator is persistent, they take up a defensive stance and lunge at them.
As octopuses are preyed upon by bigger predators, their venom is usually insufficient in killing them. They bite so their chasers become too weak to harass the octopus further.[7]
Apart from their venom, octopuses also have other self-defense mechanisms:
- Fleeing
- Camouflage
- Ink squirting
- Squeezing through small places
- Autotomy (releasing their arms at will)
Which Octopus Species Are Venomous?
All octopus species are venomous to some extent. Most species are only deadly to smaller animals, like crabs and lobsters. The deadliest octopus genus is the blue-ringed octopus, which has four species.
There is no correlation between the size of the species and its venom toxicity. The giant Pacific octopus has an immeasurably weaker venom than the blue-ringed octopus despite being 13.3 feet larger on average.
Which Octopus Species has the Deadliest Venom?
The deadliest octopus genus is the blue-ringed octopus (Hapalochlaena). There are four species in this genus:
- Greater blue-ringed octopus
- Southern blue-ringed octopus
- Blue-lined octopus
- Hapalochlaena nierstraszi
These are the only octopus species with venom potent enough to kill humans
All of the four species are small (five to eight inches) and rarely attack unprovoked. They are among the most venomous marine animal.
Each individual carries enough venom to kill 26 adult humans.[8]
Which Parts of the Blue-Ringed Octopus Are Toxic?
Although the venom is stored in the venom glands, it is distributed in the whole body of octopuses. The below table analyzes the different body parts’ toxicity, measuring it in MU/g (mouse unit, the amount of venom enough to kill a 20g mouse in 15 minutes/gram).[9]
Anything above 1,000 MU/g is classified as strongly toxic.
| Body Part | Toxicity Level |
| Salivary Glands | 9,276 MU/g |
| Hepatopancreas | 21.1–743.3 MU/g |
| Gonads | n/a–167.6 MU/g |
| Arms | 5.3–130.2 MU/g |
| Other Body Areas | 17.3–107.4 |
Are Octopuses Dangerous to Humans?
Octopus venom is generally harmless to humans. Blue-ringed octopus bites are potentially fatal. The symptoms include nausea, numbness, tight chest, and difficulty breathing. If you get bitten, seek immediate medical help.
Most octopuses only have venom strong enough to inconvenience us, but not kill us. If a human gets bitten, they most likely experience mild pain and muscle fatigue.
Octopuses’ first instinct is to flee and their bites are extremely rare. Although we shouldn’t be afraid of them in general, caution should be exercised in blue-ringed octopus-infested waters.
They live in the following areas:
- Tropical waters from Sri Lanka to the Philippines
- Australia
- Papua New Guinea
- The Solomon Islands
- Vanuatu
What Are the Symptoms of Octopus Bites?
The symptoms of octopus bites are usually mild. It’s still good practice to seek medical attention if you experience the following after an octopus bit you:[9]
- Nausea
- Numbness around the mouth, face, tongue, and neck
- Chest tightness
- Difficulty breathing
Smaller octopuses’ bites are painless, so you should check your skin after engaging them in physical contact.
What to Do if You Get Bitten by an Octopus
You will usually escape unharmed after an octopus bites you. Knowing that, your main course of action should be to remain calm.
Only the blue-ringed octopuses are toxic enough to cause fatality.
If you are bitten by an octopus, you should do the following:
- Call for an ambulance and seek medical help
- Apply pressure immobilization bandages
- Stay in company
- Apply assisted respiration
- Remain under medical care and artificial respiration until venom wears off
Regardless of what type of octopus bites you, you should always exercise caution. There is no antivenom for blue-ringed octopus bites, so you must seek professional help and remain until your condition is stabilized.
Conclusion
All octopus species are venomous. Their venom is stored and produced in venom glands and injected by saliva. Octopuses either bite or release saliva into the water. Octopuses use their venom when they hunt or as a last form of self-defense.
The deadliest octopuses are the blue-ringed octopuses. Symptoms include nausea, numbness, chest tightness, and breathing difficulties. The venom can cause death by suffocation, respiratory arrest, heart failure, or cerebral hypoxia. If bitten, seek immediate medical help.
FAQs
Are Octopuses Venomous or Poisonous?
Octopuses are venomous. The difference between venomous and poisonous is the injection method. Poisonous implies that the toxin gets into the body via consumption or contact. Venomous animals directly inject their venom into the body by biting or stinging.
How Many People are Killed by Octopuses?
There have only been about eleven human fatalities caused by octopuses. Although blue-ringed octopuses are highly toxic, their bite resulting in a fatality is extremely rare. Most people bitten by octopuses survive.
Are Squids Venomous?
Yes, squids are venomous. Squids are cephalopods (like octopuses) and most cephalopod species are venomous. Apart from squids and octopuses, cuttlefishes are poisonous cephalopods as well.
