If you’ve ever fallen into a pool, you know: the water is surprisingly hard if you hit it at the wrong angle. But many kingfisher species dive headfirst into the water to catch their fishy prey. In a new scientific journal study Biology of Communicationresearchers compared the DNA of 30 different kingfisher species to zero in on genes that may help explain the birds’ diet and ability to dive without brain damage.
The type of diving that kingfishers do — which researchers call “plunge-diving” — is an aeronautic feat. “It’s a quick dive from air to water, and it’s done by very few bird species,” said Chad Eliason, a research scientist at the Field Museum in Chicago and the study’s first author. But this is a potentially dangerous behavior.
“For kingfishers to dive headfirst the way they do, they must have evolved other characteristics to prevent them from injuring their brains,” said Shannon Hackett, associate curator of birds at the Field Museum. and the senior author of the study.
Kingfisher, copyright Dean Eades, from surfbirds gallery
Not all kingfishers actually fish – many species of these birds eat ground-dwelling prey such as insects, lizards, and even other kingfishers. Previously, co-authors Jenna McCollough and Michael Andersen, researchers from the University of New Mexico, led the team in using DNA to show that groups of fish-eating kingfishers were not closest to each other. relative to each other within the kingfisher family tree. That means kingfishers evolved their fishy diets — and the diving skills to get them — several times, rather than all evolving from a common fish-eating ancestor.
“The fact that there are so many transitions in diving is what makes this group both fascinating and powerful, from a scientific research perspective,” Hackett said. “If a trait has evolved many different times independently, that means you have the power to find a general explanation for why that is.”
For this study, researchers – including co-authors Lauren Mellenthin who is currently at Yale University, but an undergraduate intern at the Field Museum at the time this research was conducted, Taylor Hains at the University of Chicago and Field Museum, Stacy Pirro at Iridian Genomes, and Michael Anderson and Jenna McCullough at the University of New Mexico — analyzed the DNA of 30 species of kingfishers, both fish-eating and non-fish-eating.
“To get all the kingfisher DNA, we used specimens in the Field Museum’s collections,” said Eliason, who works at the Field’s Grainger Bioinformatics Center and Negaunee Integrative Research Center. “When our scientists do fieldwork, they take tissue samples from the bird specimens they collect, such as pieces of muscle or liver. Those tissue samples are stored in the Field Museum, frozen in liquid nitrogen, to preserve the DNA.”
At the Field’s Pritzker DNA Laboratory, researchers began the process of sequencing the entire genome for each of the species, generating the entire genetic code of each bird. From there, they used software to compare the billions of base pairs that make up these genomes to look for genetic variations shared by diving kingfishers.
Scientists have discovered that birds that eat fish have some altered genes related to diet and brain structure. For example, they found mutations in the birds’ AGT gene, which is associated with food adaptation in other species, and the MAPT gene, which codes for tau proteins associated with feeding behavior. .
Tau proteins help stabilize small structures within the brain, but the accumulation of too much tau protein can be a bad thing. In humans, traumatic brain injuries and Alzheimer’s disease are associated with a buildup of tau. “I learned a lot about tau protein when I was the concussion manager for my son’s hockey team,” Hackett said. “I started to wonder, why don’t kingfishers die because their brains turn to mud? There must be something they are doing that protects them from the negative influences of repeatedly landing their heads above water.
Hackett suspects that tau proteins may be something of a double-edged sword. “The same genes that keep your neurons in your brain all nice and ordered are the things that fail when you get repeated concussions if you’re a football player or if you have Alzheimer’s,” says he. “My guess is that there is some kind of strong selective pressure on those proteins to protect the birds’ brains in some way.”
Now that these correlated genomic variations have been identified, Hackett says, “the next question is, what do the mutations in these birds’ genes do to the proteins that are made? What shape changes are there? What happens to compensate in a brain for chaotic forces?”
“Now, we know which of the underlying genes are changing that help create the differences we see throughout the kingfisher family,” Eliason said. “But now that we know which genes to look at, it creates more mysteries. That’s how science works.”
In addition to a better understanding of kingfisher genetics and potential implications for understanding brain injuries, Hackett said this study is important because it highlights the value of museum collections.
“One of the specimens we got DNA from in this study was thirty years old. At the time it was collected, we couldn’t do anywhere near the kind of tests we can do today — we couldn’t do the some of these things five years ago,” Hackett said. “It brings back the ability of individual specimens to tell new stories over time. And who knows what we’ll learn from these specimens in the future? That’s why I love museum collections.”
