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The Most Toxic Animal on Earth

Pain and discomfort are the usual side-effects of a sting from one of the 4000 species of jellyfish, however, the Box Jellyfish (Cubozoan) is fatal and known to be the most toxic animal on Earth. The jellyfish that lives in tropical and temperate seas kills between 20 and 40 people a year in the Philippines alone. Its sting is so painful that it leaves most victims in shock and struggling to return to shore and can stop the heart of victims in as little as 5 minutes. The name is derived from its cubic shape with 4 long tentacles attached to each of the corners and reaching up to 3 meters in length.

How Does it Sting?

Each tentacle is filled with rows of hundreds of thousands of specialised cells that contain a capsule called a nematocyst which is capable of firing a tiny harpoon at over 60km/h. The venom is contained within a hollow thread attached to the harpoon that is injected into the body of the struck victim (See figure 1)

[Figure 1]

But How Do They Kill You?

There is still debate regarding what causes the death of victims as different researches support different theories about how the toxins target the heart.


1 – Ion channel blockers


Some researchers argue that ion channel blockers released in the toxin will prevent the movement of ions across the membrane of nerve and muscle cells, including the cells in the heart muscle, causing them to stop functioning properly and eventually leading to cardiac arrest.


2 – Specific proteins


Others argue that there are specific proteins contained in the venom that target the heart’s muscle cells which eventually leads to cardiac arrest.


3 – Porins


Angel Yanagihara from the University of Hawaii (UH) in Honolulu argues that the porins (pore forming proteins) poke holes in red blood cells causing them to leak out their potassium ions. High levels of potassium in the blood, also known as hyperkalaemia, causes cardiac arrest.

What Are You Meant Do if You are Stung?

Again, there is debate over the course of action that should be taken on the victim depending on which theory you support. Yanagihara tells us to apply vinegar onto the sting as it can deactivate unfired nematocysts followed by a copper gluconate paste which she claims to have found inhibits porins. Jamie Seymour from James Cook University in Cairns, Australia, questions whether Yanagihara’s paste can save lives and argues that the vinegar may harm victims further as in a study published in a 2014 paper, him and his team claim that vinegar can cause nematocysts that have already fired to release more venom. He recommends no treatment for victims suffering from cardiac arrest apart from cardiopulmonary resuscitation in order to maintain the blood pumping to the victim’s brain until the heart starts to beat again.

How Can We Settle This Debate?

The only way to settle this debate is to continue research regarding Box Jellyfish venom and its treatment, however, due to lack of funding in the field, this may take longer that we would hope. If researchers were able to use hard evidence regarding the number of victims of the fatal sting every year, funding may increase to support the research currently taking place.

Written by Maya Lemaire,
Grad 20 Student at Bangkok Patana School


Peschak, T. (2019). National Geographic. [online] National Geographic. Available at: [Accessed 13 Apr. 2019]. (2018). Science Magazine - November 9, 2018 - page21. [online] Available at: [Accessed 13 Apr. 2019].

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