If dissecting toads in biology class made you squeamish, it’s probably best to look away now. But if you're among the not-so-faint of heart, we're getting up close and personal with one of the world's deadliest animals to find out what its venom does to a beating heart. 

The box jellyfish (genus Cubuzoa) has earned quite the reputation – even Will Smith has felt its wrath. But contrary to popular belief, a sting from the ghostly invertebrate isn't always a death sentence. In 2011, famed swimmer Diana Nyad was stung by not one, but an entire school of box jellies, an experience she likens to being dipped in hot, burning oil and set of fire. 

Each of the jelly's tentacles contains some 5,000 stinging cells, which fire into the flesh within milliseconds, releasing a potent venom that causes everything from inflammation to rapid heart rate, difficulty breathing, back pain, brain haemorrhaging and, oh, Irukandji syndrome – an anxiety trigger that tells your brain it's about to die.  

It might seem gruesome, but experiments like the one performed on this neurologically dead toad will help us better understand how box jellyfish venom affects different parts of the body, so that we might learn to respond in emergencies. 

In the wild, the sting is used for more than defence against the dark arts ... er, predators. Unlike many jellies, the 50 or so species of box jellyfish are active hunters and can dispatch their venom with precision – something that's helped them stick around for six hundred million years!

Their bells contain 24 light-sensitive eyes, allowing the jellies to see what's coming, even if that something is oblivious to the lurking danger.


Top header image: Guido Gautsch