Tag Archives: spines

Macro cat tongue.

Cat’s tongues are surprisingly complex — and better at cleaning than any brush we have

Cat’s scaly tongues are actually very, very good at cleaning fur. So good, in fact, that they could teach our doctors and engineers some tricks, a new study reports.

Macro cat tongue.

Image credits Jennifer Leigh / Wikimedia.

Feline owners out there will know that their pet’s tongue can be really scratchy — especially when they’re grooming. One team of researchers from Georgia Tech wanted to know why. Their research reveals how the rough tongues help cats clean their thick fur and cool down on hot days.

Rough around the middle

“Their tongue could help us apply fluids, or clean carpets, or apply medicine” to hairy areas on our body, says lead researcher Alexis Noel.

The secret behind the feline tongue’s roughness — and its superb cleaning ability — is a layer of tiny hooks that cover the surface. These hooks have groove- or scoop-like structures that help them drive saliva deep into the fur. They’re really effective at it, too. The team says these structures can help inspire new inventions for a wide range of application. Noel himself is already seeking a patent for a 3D-printed, tongue-inspired brush.

Cats, when not busy presenting us with dead presents, spend a lot of time grooming their fur; around a quarter of their waking hours are invested in personal hygiene, the team reports. Given how thick their fur can get, and how hard licking it clean seems to be, this isn’t really surprising at first glance. However, Noel’s curiosity was piqued when she witnessed her cat getting its tongue stuck in a fuzzy blanket. She wondered why her pet’s tongue is covered in those cone-like bumps. Luckily for us all, her lab has a background in animal-inspired engineering — so she set out to find the answer.

The team started by taking computerized tomography (CT) scans of cats’ tongues. This step revealed that the ‘cones’ are, in fact, hooks shaped much like a cat’s claws. They typically lie with their barbs pointing towards the neck (i.e. out of the way), until a certain tongue muscle springs into action. At that point, the spines spring straight up.

What really surprised the team, however, was that these spines (called papillae) contain hollow scoops. The researchers obtained preserved feline tongues (from zoos and taxidermists) to study — bobcats, cougars, snow leopards, lions, and tigers all share this trait, the team explains. Papillae were only slightly longer in lions than in housecats, although the tongues of larger felines hold many more such structures.

Feline Papillae.

Comparison of feline papillae from CT scans.
Image credits Alexis Noel / Georgia Tech.

When dabbed with drops of food dye, these spines absorbed the liquid. Noel’s team estimates that a housecat’s papillae (roughly 300) hold saliva and release it when pressed against fur — and ensure that the animal can thoroughly clean its mane. Lab tests with a machine that the team constructed to mimic the strokes of a cat’s grooming showed that saliva from the tongue’s surface alone simply can’t penetrate as deep.

The team also measured cat fur. Our pets are usually quite fuzzy since their manes try to trap as much air as possible to insulate the animal. When compressed, however, the thickness of fur matches the length of these spines in many types of cat, the paper adds. One exception is Persian cats with their super-long fur that veterinarians caution must be brushed daily to avoid matting.

Finally, these spines aren’t just about staying clean — a thermal camera showed evaporating saliva cooled the cats as they groomed.

The paper “Cats use hollow papillae to wick saliva into fur” has been published in the journal Proceedings of the National Academy of Sciences.

How the human penis lost its spines

It’s been long theoretized by most women, and not only, that there is a connection between the penis and the brain – and research done by Gill Bejerano, a biologist at Stanford University School of Medicine, and colleagues seems to support that theory, at least in a way.

Let’s look at our close relatives, the chimpanzees. Humans and chimps share over 97% of DNA, but it’s safe to say that between them and (most) humans there are some major differences in terms of appearance, and especially intellect. For example, we know that humans have larger brains, and within the brain, specifically a bigger angular gyrus, a region associated with abstract concepts, among others.

We also know that chimps have smaller penises which also have spines; don’t think about hedgehogs or anything, but just enough to make it… a little bumpy.

The team of researchers in case wanted to have a deeper understanding (no pun intended) of why these differences appear, so they analyzed genomes of humans and closely related primates and discovered more than 500 regulatory regions (the points which tell genes what to do) that chimps and other primates have, and humans don’t. In other words, they found out what parts of the genome humans lost through millions of years of evolution.

Think about it in terms of lightbulbs and switches: the light bulbs are the genes, while the switches are these DNA controlling sequences. If you have no bulb, you can’t turn it on and off; now think about a bulb that has five different switches that control it and can turn it on in different places and at different times. If you take one of them away, the bulb still works in four situations, but not in the fifth.

The study basically looked at two of these switches, and in order to analyze them, they took the switch information from chimps and hooked it up to what is called a receptor gene, a gene whose effects can be easily tracked. They injected this information into a mouse egg, to track the progress. They found that one switch makes sensory whiskers develop on the face and spines on the penis.

“This switch controls the expression of a key gene that’s required for the formation of these structures,” said David Kingsley, a study co-author at Stanford University. “If you kill that gene — smash the lightbulb — which has been done previously in mouse genetics, the whiskers don’t grow as much and the penile spines fail to form at all.”

You can read the full article over at Nature.

“It is detective work and a great reminder that, in the course of evolution, information is both gained and lost,” said Sean Carroll, an expert in animal genetics and evolution at the University of Wisconsin, Madison.

“As so often with very good ideas, it seems almost obvious in hindsight,” said Svante Pääbo, who directs the genetics department of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and was part of the team that recently sequenced the Neanderthal genome. “Since two of the almost 500 deleted sequences they identified turn out to be interesting, I am sure that several other ones on their list will turn out to be interesting too,” he added. The researchers are continuing to analyse the remaining 508 DNA sequences.