Last updated July 18, 2018 at 3:09 pm
They can handle heat that would make us weep (or worse).
When it comes to handling heat from the kitchen, it seems the Chinese tree shrew is on another level.
Scientists from Kunming Institute of Zoology have discovered that Tupaia belangeri chinensis remains unaffected by even the hottest of chillies because it has evolved different pain cells.
Chillies aren’t naturally a part of its diet, but a plant it does favour – Piper boehmeriaefolium – produces high levels of capsaicinoids, the chemicals that give chillies their punch.
The researchers found that the mammal, a close relative of primates, is unaffected by this active ingredient due to a subtle mutation in the receptor that detects it. They speculate that this is an evolutionary adaptation to allow it to make the peppery plant a part of its diet.
Capsaicinoids, including the capsaicin found in chillies, act by triggering the activation of TRPV1, an ion channel found on the surface of pain-sensitive cells in the tongue and elsewhere.
That sharp burning sensation
TRPV1’s normal job is to alert animal to the presence of harmful heat, which is why capsaicinoids induce a sharp burning sensation. While humans may develop a tolerance and even a liking for them, most animals avoid eating plants that contain them.
During trials, tree shrews did not reduce their food intake when the heat was increased, whereas mice did. While the levels of TRPV1 were similar, and the mammals were similarly responsive to other painful stimuli, the TRPV1 ion channel in the tree shrew was much less responsive to capsaicin.
The reason, the authors say, is that the TRPV1 proteins of mice and tree shrews differ by a single amino acid in the binding pocket for capsaicin, a mutation that reduces the binding ability, and thus pain-inducing potential, of capsaicin in the tree shrew’s form of the protein.
The ability to feed on a plant most other species avoid it, they say, is potentially an important driver for the spread of the TRPV1 mutation through the tree shrew population over time.
The paper published in PLOS Biology.