1. Box jellyfish
Often touted as the most venomous animals in the world, box jellyfish (Chironex fleckeri) cruise tropical waters around northern Australia, Papua New Guinea, Thailand, Indonesia, the Philippines and Vietnam. Each jellyfish has about 60 tentacles, each with up to 50 million nematocysts, specialised stinging cells that release like a spring when brushed. The venom leads to skin necrosis and pain so severe it can send you into shock. Death is caused by cardiovascular collapse. The exact toxins aren’t well known, but affect the heart (a cardiotoxic substance), nervous system (neurotoxic) and skin cells (dermatonecrotic) and also cause red blood cells to burst (haemolytic).
2. Funnel-web spider
Funnel-web spiders (Atrax and Hadronyche species) haunt backyards and forest regions around Australia, with some species, such as the Sydney funnel-web (Atrax robustus), having a more limited and self-explanatory geographical range. Males have more virulent venom and are more likely to attack than females (although females will if provoked) and roam outside their burrows during the spring/summer months, looking for mates.
Interestingly, the venom of funnel-webs is more toxic to primates than other mammals – despite the fact that primates aren’t their intended prey. Initial symptoms include tingling around the mouth, excessive salivating and sweating, muscle twitching and spasms which progressively worsen and lead to tachycardia (heart beating too fast) then hypotension. Antivenom is now widely available.
A native Australian species found in remote, arid regions in the red centre, the inland taipan (Oxyuranus microlepidotus) and its coastal cousin (O. scutellatus) from northern Australian coasts, are two of the world’s most venomous snakes.
Their venom is a mixture of procoagulants (agents that promote blood clotting), and highly potent neurotoxins – effectively poison for nerve cells – which form the “killing molecules”, says Ken Winkel, director of the Australian Venom Research Unit at the University of Melbourne. The bite of the coastal taipan contains 50 times the median lethal dose as the king cobra and about 100 times as many as the eastern diamond rattlesnake. The neurotoxins disrupt communication between nerves, causing paralysis and subsequent death.
4. Blue-ringed octopus
The deadly blue-ringed octopus (Hapalochlaena species) dwells in tidal pools and open water across the western Pacific Ocean from Australia to Japan. Biologists originally thought the octopuses produced and stored venom in their salivary glands, but recent research has shown that the venom is produced by a bacterium that lives symbiotically within and all over the octopuses’ bodies. This bacterium is particularly concentrated in the octopuses’ tentacles. Blue-ringed octopuses can be selective in their venom administration; they have one type of venom that they use for killing their prey and another type for their own defence.
5. Brazilian wandering spider
Particularly dangerous because of its roving nature, this spider (Phoneutria nigriventer and Phoneutria fera) from tropical central and South America has ‘fangs’ – which are actually modified legs covered in red fur – that inject venom into their victims. Once injected, the victim may experience muscular paralysis leading to respiratory or cardiac arrest. As an unexpected side effect, the toxin also causes nitric oxide release, which can cause priapism – an involuntary erection “so hard you can charge it through a brick wall,” says biochemist Bryan Fry of the University of Queensland in Brisbane.
6.Golden poison dart frog
The golden poison dart frog (Phyllobates terribilis) lives in the rainforest on the Colombian coast. Their extremely potent toxin is transferred via their skin, secreted by glands behind the frog’s ears. Some scientists believe that the frogs sequester their venom through their diet, as frogs kept in captivity lose toxicity. Called batrachotoxin, the active component primarily affects the heart causing arrhythmias, fibrillations and eventually cardiac arrest. It also increases sodium permeability, which amplifies communication in the nervous system, putting it into overdrive.