Australia Has Venomous Snakes, Spiders, And… Trees [gizmodo.com]:
From snakes and spiders to jellyfish and cone snails, Australia has no shortage of venomous animals [australiangeographic.com.au]. As new research [sciencemag.org] published in Science Advances shows, Australia even harbors venomous plants belonging to the Dendrocnide genus, namely Dendrocnide excelsa and Dendrocnide moroide, both of which are known as “gympie-gympie” in the local indigenous Gubbi Gubbi language.
[...] Dendrocnide plants are “notorious for producing [an] excruciatingly painful sting, which unlike those of their European and North American relatives can cause symptoms that last for days or weeks,” Irina Vetter, a co-author of the study, explained in a press release [uq.edu.au]. Similar to other nettles, the stinging tree “is covered in needle-like appendages called trichomes that are around five millimetres in length,” she said. They look like fine hairs but “actually act like hypodermic needles that inject toxins when they make contact with skin,” said Vetter, an associate professor at the University of Queensland.
[...] In the state of Queensland, it is not uncommon to find warning signs along forest tracks, alerting unwary visitors to the presence of Dendrocnide species and the potency of their sting. This signage is justified given that D. moroides has been implicated in hospitalization of two individuals requiring intensive care for 36 hours who suffered from acute pain that reportedly did not respond to morphine and ongoing symptoms lasting months. This long-lasting pain is also typical of other Dendrocnide species stings, with episodic pain typically subsiding over several weeks, although [painful tingling and prickling sensations] may persist longer.
[...] As the new research shows, this toxin makes permanent alterations to the sodium channels in sensory neurons. Sodium channels are a membrane protein that play a critical role in the formation of pain, which they do through the excitation of neurons. In tests, gympietides was shown to activate the sensory neurons of mice and then prevent them from shutting back down. So this venom—in addition to generating the pain signals—interrupts the mechanism responsible for stopping those signals. That is, in a word, nasty, and it explains why pain sometimes lasts so long after the encounter with the tree.
Edward K. Gilding, Sina Jami, Jennifer R. Deuis, et al. Neurotoxic peptides from the venom of the giant Australian stinging tree [open], Science Advances (DOI: 10.1126/sciadv.abb8828 [doi.org])