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How do kingfishers dive without hurting their brains?

With their striking appearance and remarkable hunting skills, kingfishers are fascinating creatures. In a recent study, scientists have taken a closer look at the genetic makeup of these birds to understand the secrets behind their unique ability to plunge-dive into water without harming their brains.

Diving headfirst

Imagine diving headfirst into a pool – it’s no easy feat. The force of the water can be surprisingly jarring, even more so when approached at an incorrect angle. 

Yet, the kingfisher seems to have mastered this act, diving headfirst to catch fish. The question is: how do they manage this without sustaining any brain damage?

Focus of the study 

The study, published in the journal Communications Biology, was focused on a comparison of the DNA of 30 different kingfisher species. The goal was to identify genes that could give insight into the birds’ specialized diet and their unique diving abilities. 

Chad Eliason, the study’s first author and a research scientist at the Field Museum in Chicago, said: “It’s a high-speed dive from air to water, and it’s done by very few bird species.” The potential risk of such dives has made the kingfisher’s ability a point of scientific intrigue.

“For kingfishers to dive headfirst the way they do, they must have evolved other traits to keep them from hurting their brains,” said study senior author Shannon Hackett.

This theory is further supported by the fact that not all kingfishers have a fish-centric diet. Some eat land-based prey such as insects, lizards, and even other kingfishers. 

Diverse evolution 

Prior research by co-authors Jenna McCollough and Michael Andersen, both from the University of New Mexico, revealed that kingfishers evolved their fish-eating habits multiple times rather than from a single 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,” says Hackett. “If a trait evolves a multitude of different times independently, that means you have power to find an overarching explanation for why that is.”

How the research was conducted 

To investigate, the researchers analyzed the DNA of 30 species of kingfishers. They sourced the kingfisher DNA from specimens at the Field Museum’s collections. Using advanced sequencing techniques, they generated the entire genetic code of each bird.

The analysis revealed that diving kingfishers had several genetic modifications related to diet and brain structure. Notably, mutations were found in the AGT gene, associated with dietary flexibility in other species, and the MAPT gene, which is linked to tau proteins affecting feeding behavior. 

Tau proteins 

The role of tau proteins is critical. They stabilize structures inside the brain, but an excess can be harmful. In humans, for instance, conditions like traumatic brain injuries and Alzheimer’s are tied to a buildup of tau. This raises questions about how kingfishers mitigate the risks associated with frequent diving.

Hackett’s own experience sparked her curiosity about tau proteins. “I learned a lot about tau protein when I was the concussion manager of my son’s hockey team.” 

“I started to wonder, why don’t kingfishers die because their brains turn to mush? There’s gotta be something they’re doing that protects them from the negative influences of repeatedly landing on their heads on the water’s surface.”

Selective pressure 

Hackett suspects that tau proteins may be something of a 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.”

“My guess is there’s some sort of strong selective pressure on those proteins to protect the birds’ brains in some way.” 

The team’s next challenge is to understand how these genetic mutations impact the proteins produced and how these changes equip the bird’s brain to handle the stresses of diving.

“Now, we know which of the underlying genes are shifting that help create the differences that we see across the kingfisher family,” said Eliason. “But now that we know which genes to look at, it created more mysteries. That’s how science works.”

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