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Australia has venomous snakes, spiders and … trees



Hair-like stem structures of Dendrocnide excelsa.

Hair-like stem structures of Dendrocnide excelsa.
Image: Institute of Molecular Biology / University of Queensland

Australia’s famous stinging trees cause agonizing pain that can last for weeks or even months. New research shows that this relative of nettle is actually poisonous, producing a toxin that is not unlike spider venom.

From snakes and spiders to jellyfish and snails, Australia has no shortage of poisonous animals. Like new research published in Science Advances shows Australia even hosts poisonous plants belonging to the genus Dendrocnide, namely Dendrocnide excelsa and Dendronide moroid, both of which are known as “hippies-hippies” in the local language Gubbi Gubbi.

Hippie-hippie plants look harmless, but their stems and leaves pack an unpleasant blow.

Hippie-hippie plants look harmless, but their stems and leaves pack an unpleasant blow.
Image: University of Queensland

A chemical analysis conducted by researchers at the Institute of Molecular Biology at the University of Queensland in Brisbane has led to the discovery of an entirely new family of toxins called “hypimetides”, which are produced by the Dendronide plant. According to researchers, this toxin is surprisingly similar to the venom found in spiders and cone-shaped snails.

These trees grow in Eastern Australia, especially on the slopes and ravines of tropical forests. Dendronide trees technically belong to the family of nettle plants, which are known to produce annoying stings, but “they are much more than large nettles,” the study authors wrote. The stems and oval leaves of these trees are covered with needle-like hairs, and anyone who has enough misfortune to rub in them expects a nasty surprise.

Dendronide plants are “known for their production [an] an excruciatingly painful sting that, unlike those of their European and North American relatives, can cause symptoms that last for days or weeks, ”explains Irina Veter, co-author of the study. press release. Like other nettles, the stinging tree “is covered with needle-like appendages called trichomes, which are about five millimeters long,” she said. They look like fine hairs, but “actually act like subcutaneous needles that inject toxins when they come in contact with the skin,” said Veter, an associate professor at the University of Queensland.

In fact, these plants are no joke, as the researchers explain in their report:

In the state of Queensland, it is not uncommon to find warning signs on forest paths, warning reckless visitors about the presence of Dendroclid species and the strength of their stings. This designation is justified in view of this D. moroides was involved in the hospitalization of two people in need of intensive treatment for 36 hours, who suffered from acute pain that was reportedly unresponsive to morphine and continued symptoms lasting months. This long-term pain is also typical of other dendronide stings, with episodic pain usually decreasing over several weeks, although [painful tingling and prickling sensations] may last longer.

Scientists have tried to explain these exaggerated effects on health, as the extensive, long-lasting sting does not appear to be caused by the fine hairs that get into a person’s skin. Moreover, neurotransmitters and inflammatory mediators such as histamine, acetylcholine and formic acid do not cause the observed pain effects, although they are found in trichomes. For the new study, Vetter and colleagues sought to find a potentially neglected neurotoxin in both dendronide trees, leading to the discovery of the hypimetid molecule.

Needle-like hairs inject toxins when touched.

Needle-like hairs inject toxins when touched.
Image: University of Queensland

“Although derived from a plant, gimpetites are similar to spider and cone snail toxins in the way they fold into their 3D molecular structures and target the same pain receptors – this may make the hippie-hippie tree really “Poisonous plant,” Wind said in a University of Queensland publication.

Interestingly, this may be an example of convergent evolutionin which similar traits occur in unrelated species. What makes this a particularly unique case, however, is that this same trait – venom – has appeared in plant and animal. This is unusual, as convergent evolution is often driven by similar pressures on the environment and lifestyle.

As the new study shows, this toxin makes permanent changes in the sodium channels in sensory neurons. Sodium channels are membrane proteins that play a critical role in the formation of pain, which they do by exciting neurons. During the tests, it was shown that gymnasts activate the sensory neurons of mice and then prevent them from being switched off again. So this poison – in addition to generating pain signals – disrupts the mechanism responsible for stopping these signals. That is, in a word, nastyand explains why the pain sometimes lasts so long after meeting the tree.

The good news is that “by understanding how this toxin works, we hope to provide better treatment for those who have been stung by the plant to relieve or eliminate the pain,” Wind said.

Which, thank God. I was stung by a “normal” nettle and it was completely unpleasant. It’s hard for me to imagine these sensations that last more than a few minutes, let alone days or weeks. Effective treatment of these poisonous trees would be the best development.


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