Welcome to the Curious Meerkat newsletter for October.
The summer is finally drawing to a close, and it’s time for the September Curious Meerkat Newsletter!
This month I finally published the first part of my new series, “There’s No Such Thing as Natural“, looking at genetically modified organisms and the connotations of the word “natural”.
As we all know, natural automatically means good. Nothing in nature has ever hurt anyone, ever.
In the first part of my series deconstructing the term ‘natural’, I talk genetically modified organisms and domestication, and ask what is really natural, anyway?
Welcome to this month’s Curious Meerkat Newsletter.
This month I wrote a short piece on Chinese tree shrews, which have evolved a slightly different receptor on their tongue that allows them to eat large quantities of spicy food.
Virtually all mammals wisely choose to avoid eating chilli peppers and other foods that taste ‘hot’. New research shows that Chinese tree shrews have evolved to eat large quantities of chillies in their diet by tuning down their taste buds to the chemical that makes these foods spicy.
Yalan Han of the Kunming Institute of Zoology in China, and their colleagues found that Chinese tree shrews (Tupaia belangeri chinensis) in the lab were happy to feed on chilli peppers, unlike lab mice which stop eating food if it’s too spicy. To see whether this unusual behaviour was due to reduced numbers of pain receptors on the tongue, or reduced sensitivity of those receptors, the team looked at gene expression patterns and found that while mice and tree shrews had similar numbers of pain receptors, the tree shrews’ receptors were less responsive to capsaicin – the chemical that gives chillies their spice.
Tree shrews are thought to share a relatively recent common ancestor with primates, just 85 million years ago.
Spiciness is down to chemicals called capsaicinoids, which include capsaicin in chilli peppers and related chemicals in peppery plants like Piper boehmeriaefolium, which is naturally abundant in Chinese tree shrew habitat. These compounds evolved to prevent herbivores eating the leaves and stems of plants that produce them – chemical warfare against would-be attackers. Capsaicinoids stimulate the TRPV1 receptor which is found on the surface of pain-sensitive cells, particularly those on the tongue. TRPV1 receptors are designed to detect dangerously hot food and produce a pain response to protect the animal from burning itself, but evolution has exploited a quirk in their structure meaning they are also triggered by dietary compounds like capsaicin.
Looking to the genome, the team were able to track the reduced sensitivity of the tree shrews’ TRPV1 receptor to a mutation that made a single amino acid change – just one link in the protein chain – at the site that capsaicin binds, making the receptor less likely to bind capcaisin molecules that hit it. This simple change makes the shrews taste less of the spiciness of their food.
The ability to feed on Piper boehmeriaefolium and other spicy plants that are common in the tree shrews’ natural environment may have driven evolution of this simple but effective way to increase tolerance to spicy foods.
The moral of the story is this – never get into a chilli-eating contest with a tree shrew.
Want to Know More?
Ticks feed on the blood of vertebrates, but this diet is low in B vitamins, which are vital for cellular metabolism. A study published earlier this year shows that African soft ticks (Ornithodoros moubata) supplement their diet with vitamin B from bacterial symbionts.
Parasites are thought to diversify with their host species, but the theory has rarely been tested. Kevin Johnson at the University of Illinois and his colleagues sequenced the genomes of 46 species of lice that parasitise birds or mammals, and two non-parasitic bark lice, and constructed an evolutionary tree. They estimated that parasitic lice first emerged between 90 and 100 million years ago, but didn’t begin to diversify until 66 million years ago – around the time of the dinosaurs’ extinction.
This month I’ve been working on a book proposal, which has been keeping me very busy, as well as a couple of blogs that will also be comedy sets!
I wrote a short piece about social immunity in acrobat ants.
As I’ve mentioned before, living in a large densely-packed social group, like a city or an ant colony, comes with some drawbacks – perhaps worst of which is the risk of catching a contagious diseases. Earlier this year I wrote about research showing that raider ants treat injured workers’ wounds, helping them to heal. Now, a new study shows that the queen can pass on resistance to diseases she’s encountered, arming her workers against pathogens.
This month I’ve been away in California, so I’ve been less productive than usual. Back to normal for April! But I did finish the article I promised you last month, about social medicine in ants, which was a lot of fun to write.
I’m looking for interesting new blog topics for 2018, so please send me your science questions!