Meet the Box Jellyfish, the Most Venomous Marine Animal
Box jellyfish are fascinating animals — but only from a distance.
The box jellyfish sting packs a serious wallop and can cause death in a matter of minutes. Learn all there is to know about this unusual creature, including how you can avoid getting hurt.
So What Are Box Jellyfish?
Despite their moniker, jellyfish aren’t fish. They’re Cnidaria, a diverse group of animals that are armed with stinging cells, or nematocysts. All Cnidaria have stingers that they use to paralyze and capture prey.
There are four groups of Cnidaria:
- Anthozoa: True corals, anemones and sea pens
- Cubozoa: Box jellies
- Hydrozoa: Siphonophores, hydroids, fire corals and medusae
- Scyphozoa: True jellies
Box jellyfish are basic creatures with a lifespan of about six months. They have no blood, brain or heart. They consist of three layers (an epidermis, mesoglea and gastrodermis), a nervous system and a single-opening digestive cavity for eating and releasing waste.
While most jellies float along with the current, box jellies can actually swim.
There are approximately 50 types of box jellies in the world's oceans. The largest can be up to a foot wide with 10-foot long tentacles.
The Box Jelly's Habitat
Box jellies live in warmer waters all over the world. They prefer coastal areas and often occupy reefs, coasts and mangroves.
The most lethal box jellies live in the Indo-Pacific region and northern Australia, but that doesn't mean their stings aren't lethal elsewhere.
The (Jelly) Eyes Have It
Unlike other jellies, the box jellyfish's eyes are complex. They have 24 eyes located in the middle of their bell. Their upper and lower peepers can detect images and allow them to navigate and avoid obstacles, while the other two sets are relatively primitive.
Their eyes help them detect food 10 meters (32.5 feet) away. Their visual field is nearly 100 degrees. Box jellies are carnivores. They live on small fish and invertebrates.
The Jelly's Potent Venom
Not all jelly toxins are created equal, but they are painful. Some can poison a human, particularly their heart and red blood cells, within minutes of the initial sting. Immediate treatment for the box jelly's sting is paramount. When left untreated, their sting has often resulted in fatalities.
Over the past 100 years, Australian researchers have recorded at least 64 deaths from the box jelly's venom. In 2016, a study reported that, of the 15 stings recorded off the coast of Thailand, six were fatal.
What Happens When Someone Is Stung by a Box Jelly
Box jellies are most transparent when in the water. When someone accidentally brushes up against a jelly, its stingers pierce their skin, allowing the venom to enter their bloodstream.
Jellyfish stings mostly occur in adult males in waters of 100 meters (328 feet) or less, in people in the ocean during an outbound tide (between 3 and 6 p.m.) and in children, who are more in danger of fatality due to their smaller bodies.
The bigger the jelly, the more serious the sting will be. If the length of the victim's skin welts are more than 70 centimeters (2 feet), they must get immediate medical attention, as unconsciousness and death are likely.
Initial symptoms of a sting are typically burning pain, blisters and welts. Tentacles from the jellyfish may be stuck on the skin, and the victim may exhibit unusual behavior as a result of the pain.
If the sting goes untreated, the victim may develop Irukandji syndrome. Symptoms include back pain, muscle cramps, nausea and vomiting, hypertension, tachycardia and cardiac arrest.
Sting Treatment on the Spot
A person stung by a box jellyfish should get out of the water as soon as possible to receive medical intervention.
The sting area should be rinsed for at least 30 seconds with acetic acid or vinegar. The person attending to the victim should remove any tentacles or stingers from the body by gently applying pressure with a credit card.
When waiting for emergency responders, the person attending to the victim should monitor their breathing and pulse and prepare to administer CPR if they aren't breathing or are showing signs of cardiac arrest.
Emergency responders may continue CPR or give the victim oxygen, pain medication, anti-venom, and continue treatment by intubation or a ventilator.
Preventing Injury From a Box Jelly
If you know there are box jellies at a specific beach, avoid swimming or wading in that location. The best way to know if there have been sightings is to ask locals or a lifeguard. Some beaches may even have posted warnings.
Even walking along the shore may be dangerous when jellies are in the area, so make sure to wear water shoes. When in the water, a bodysuit, wetsuit or stinger suit will help protect you.
Beaches with lifeguards will offer immediate first aid if you get stung. However, if you are not on the beach with a lifeguard, it's best to come prepared with a first-aid kit and knowledge of what to do if a jelly sting occurs.
If the sting is minor, it can be treated at home with pain medication, antibiotic ointments, icepacks and bandages.
Box Jellyfish Explainer Video