The protein that triggers Alzheimer’s disease may help protect the brains of kingfishers when they dive headfirst into water, suggests a new study.
American researchers looking at how the birds are able to dive at speed without turning their brains to mush believe selective pressure on a particular protein could afford them protection.
A build-up of these same proteins in humans, however, is associated with Alzheimer’s and traumatic brain injuries in those who suffer repeated concussions in humans.
The researchers say their study, published in the journal Communications Biology, could improve our understanding of brain injuries as well as our knowledge of kingfisher genetics.
As anyone who has ever belly-flopped into a swimming pool from a diving board will know, water can prove a surprisingly solid surface when contacted at a certain angle.
But many species of kingfisher impressively dive headfirst into water at speed in order to catch their prey, in an aeronautic feat known as “plunge-diving.”
American researchers therefore gathered and compared the DNA of 30 different kingfisher species to hone in on the specific genes that might help to elucidate their ability to dive without sustaining brain damage.
Study first author Dr. Chad Eliason, a research scientist at the Field Museum in Chicago in the US state of Illinois, explained that though impressive, the kingfishers’ dive can also be risky.
“It’s a high-speed dive from air to water, and it’s done by very few bird species,” he said.
Dr. Shannon Hackett, associate curator of birds at the Field Museum and the study’s senior author, added: “For kingfishers to dive headfirst the way they do, they must have evolved other traits to keep them from hurting their brains.”
Not all species of kingfishers actually fish; with many eating land-dwelling prey such as insects and lizards, and others even resorting to cannibalism in eating fellow kingfishers.
A previous study from researchers at the University of New Mexico used DNA analysis to show that kingfishers who do eat fish aren’t even each others’ closest relatives within the species’ family tree.
This means the birds evolved their fishy diets – as well as the diving abilities to catch them – a number of separate times, rather than all evolving from one common, fish-eating ancestor.
“The fact that there are so many transitions to diving is what makes this group both fascinating and powerful, from a scientific research perspective,” Dr Hackett said.
“If a trait evolves a multitude of different times independently, that means you have power to find an overarching explanation for why that is.”
For this latest study, the research team examined the DNA samples of 30 species of kingfisher; including those who eat fish and those who don’t.
They sequenced full genomes – the complete set of genes in an organism or cell – thereby generating the entire genetic code of each bird.
They then compared the billions of base pairs making up these genomes to look out for genetic variations that the diving kingfishers have in common.
The scientists discovered that the fish-eating birds had several modified genes associated with diet and brain structure.
They found mutations in the birds’ AGT gene – associated with dietary flexibility in other species – and the MAPT gene, which codes for tau proteins related to feeding behavior.
These tau proteins help to stabilize tiny structures inside the brain, but the accumulation of too many of these proteins can prove problematic.
In humans, traumatic brain injuries and Alzheimer’s disease are both associated with a buildup of tau.
Dr Hackett, who learned a lot about tau protein whilst she was the concussion manager for her son’s hockey team, explained: “I started to wonder: why don’t kingfishers die because their brains turn to mush?
“There’s got to be something they’re doing that protects them from the negative influences of repeatedly landing on their heads on the water’s surface.”
Dr. Hackett says she now believes tau proteins to be a potentially double-edged sword.
“The same genes that keep your neurons in your brain in all nice and ordered are the things that fail when you get repeated concussions if you’re a football player or if you get Alzheimer’s,” she says.
“My guess is there’s some sort of strong selective pressure on those proteins to protect the birds’ brains in some way.
“The next question is: what do the mutations in these birds’ genes do to the proteins that are being produced? What shape changes are there? What is going on to compensate in a brain for the concussive forces?”
Dr. Eliason added that the study had opened up new questions, saying: “Now we know which of the underlying genes are shifting that help create the differences that we see across the kingfisher family.
“But now that we know which genes to look at, it created more mysteries. That’s how science works.”
Dr. Hackett hopes the research could help scientists further understand brain injuries, as well as the genetics of kingfishers.
But she also championed the project for highlighting the value of museum collections, saying: “One of the specimens we got DNA from in this study is thirty years old.
“At the time it was collected, we couldn’t do anywhere near the kind of analyses we can do today – we couldn’t even do some of this stuff five years ago.
“It traces back to the ability of individual specimens to tell new stories through time.
“And who knows what we’ll be able to learn from these specimens in the future?
“That’s why I love museum collections.”
Produced in association with SWNS Talker
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