Don’t Meet the Australian Box Jellyfish

Learn more about the world’s most venomous ocean animal

Isn’t the photo above gorgeous?! At first glance, you would think: “…that looks serene and beautiful.” But that beautiful ocean animal is extremely dangerous. On the flip side, when you see an animal with sharp teeth and claws, your flight or fight response kicks in and you escape! But, we have seen time and time again … smaller ocean creatures that don’t necessarily look dangerous can be extremely dangerous and even deadly. It’s always best to steer clear, give wild animals their space and avoid contact. You do not want to meet the Australian box jellyfish! Let’s learn more about them…

The Australian box jellyfish is considered one of the most venomous animals in the sea—their sting can cause cardiac arrest, paralysis or death in humans in just a few minutes. You definitely want to avoid meeting them.

Box jellyfish are cnidarians—a simple invertebrate (an animal without a backbone) that lives in the water and has a digestive cavity with only one opening. Jellyfish, sea anemones, corals and hydra are all cnidarians.

There are about 50 different species of box jellyfish, sometimes also called sea wasps. They have a cube-shaped body which helps to easily identify them and distinguish them apart from “true” jellyfish. The box jellyfish can have 24 eyes and 15 tentacles that can reach up to 10 feet in length. In the wild, box jellyfish can live up to one year.

Australian box jellyfish (Chironex fleckeri) is the largest species of box jellyfish, with tentacles up to 10 feet long. They live off the coast of northern Australia and in the Indo-Pacific.

Lethal Toxin

The tentacles of the Australian box jellyfish are covered in small darts filled with venom (nematocysts). These darts can be fired into prey at more than 37 mph. Their nematocysts contain a potent toxin that causes a spike in blood pressure, seizing up the heart and can cause serious pain or death. A single sting can cause skin necrosis, and a large enough quantity of venom will lead to cardiac arrest and death within minutes.

Marine and land animals can be stung by box jellyfish. But did you know that sea turtles survive being stung due to their thick skin that cannot be penetrated? In fact, some sea turtles love eating jellyfish—including box jellyfish. Sadly, they also often mistake plastic bag pollution for jellyfish.

Box Jellyfish in Mangroves

Warming Ocean Waters

Warming ocean waters—due to climate change—are making the ocean more habitable to jellyfish, like the Australian boxfish jellyfish. The result is that the amount of time humans can be exposed to these jellyfish is increasing. And the span of their habitat is increasing. Previously running from November through May, the Australian box jellyfish season has been extended due to the rise in sea temperatures.

You can help by taking action today! Climate change is a problem with a known solution. We need to make drastic reductions in greenhouse gas emissions in the next decade to stay below warming temperatures of 1.5°C to avoid the worst impacts of climate change. We need our leaders to match this global challenge with climate action on a scale our country has never seen before. We need you to urge our leaders to act on climate before it’s too late.

Our work is focused on solving some of the greatest threats facing our ocean today. We bring people, science and policy together to champion innovative solutions and fight for a sustainable ocean.
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