Australasian Science: Australia's authority on science since 1938

Scorpion Venom Unlocked

By Stephen Luntz

The first comprehensive study of the venom of Australian scorpions has helped understanding of the evolution of these creatures, and may lead to painkilling medications.

Australia is well-known for its dangerous snakes, spiders, jellyfish and octopi, but scorpion venom rarely gets a mention. There is a reason for that – Australian scorpions are small and most prey on small insects. “It is the prey that drives venom development with them, and it’s not designed for vertebrates so it is seldom fatal to humans,” says A/Prof Bryan Fry of the University of Queensland’s School of Biological Sciences.

Moreover, while Australian scorpions are widespread they don’t tend to venture into houses much so stings are rare. In Mexico, Fry notes, there are half a million stings each rainy season, dwarfing the impact of snakes and spiders worldwide.

While Australian scorpions may not be deadly, some species can still be extraordinarily painful while others cause numbness. “The compounds which cause numbness can be directly useful in treating pain, and the ones that cause pain can teach us a lot about how pain works and how we can reduce it.

“We have a remarkably poor grasp of how pain works,” Fry says. “These can help us discover new receptors, new receptor subtypes and binding.

“Different sorts of pain respond to different painkillers in different ways. Some sorts of pain don’t respond to any painkillers because we don’t know about those receptors. If these bind to a receptor and turn it on, a slight modification might turn it off.”

With just 0.1 mg produced by a large scorpion, the venom is hard to investigate. “Before this study, only one Australian scorpion species had been studied in detail,” Fry says. “Now we have catalogued the chemical composition of the venoms of five more species which represent the three scorpion families.”

Scorpions tie with centipedes for the oldest lineage of land-based venom, so their poisons are exceptionally evolved, making them “a rich source of molecules”. Drugs based on their venoms show promise against such unlikely targets as malaria.

“The results radically shift our understanding as to how scorpion venoms have evolved,” says Fry, with several theories of scorpion relationships overturned.

The Australian scorpions may be relatively harmless, but Fry has personal experience of their Amazon equivalents. Besides the excruciating pain for around 6 hours, his heart beat 100 times in 30 seconds and then stopped for 5–6 seconds, during which time he could feel the loss of blood.