Bat ‘nightclubs’ may be the key to solving the next pandemic
The evolution of viral tolerance in Myotis bats may help scientists prevent future pandemics, say researchers at Texas A&M.
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MYOTIS BATS ROOSTING TOGETHER
view moreCREDIT: DR. NICOLE FOLEY/TEXAS A&M UNIVERSITY SCHOOL OF VETERINARY MEDICINE AND BIOMEDICAL SCIENCES
Bats carry some of the deadliest zoonotic diseases that can infect both humans and animals, such as Ebola and COVID-19.
In a recently published article in the journal Cell Genomics, a Texas A&M research team revealed that some species of bats are protected against the viruses they carry because they commonly exchange immune genes during seasonal mating swarms.
“Understanding how bats have evolved viral tolerance may help us learn how humans can better fight emerging diseases,” said Dr. Nicole Foley, from the Texas A&M School of Veterinary Medicine & Biomedical Sciences (VMBS). “As genomicists, our work often lays the groundwork for research by scientists who study virus transmission directly. They may be developing vaccines for diseases or monitoring vulnerable animal populations. We all depend on each other to stay ahead of the next pandemic.”
Because bats are often immune to the diseases they carry, Foley and Dr. Bill Murphy, a professor in the VMBS’ Department of Veterinary Integrative Biosciences, believe that studying bats’ disease immunity could hold the key to preventing the next global pandemic.
“Because of the COVID-19 pandemic, the prediction and prevention of outbreaks is front of mind for researchers and the public alike,” Foley said. “Several bat species are tolerant of viruses that are detrimental to human health, which means they become reservoirs for disease — they carry the viruses, but crucially they don’t develop symptoms.”
The Secret Of Swarming Behavior
To uncover exactly how bats have evolved tolerance to these deadly viruses, Foley, Murphy, and their international research partners mapped the evolutionary tree of Myotis bats, something they knew to be crucial in trying to identify which genes might be involved.
“Myotis bats are the second-largest genus of mammals, with over 140 species,” she said. “They’re found almost all over the world and they host a large diversity of viruses.”
To add to the difficulties associated with figuring out relationships among species, Myotisand other bat species also engage in swarming behavior during mating.
“You can think of swarming behavior like a social gathering; there’s lots of flight activity, increased communication and inter-species mingling; for bats, it’s not unlike going to a club,” Foley said.
Complicating things for the researchers, swarming creates increased numbers of hybrids — individual bats with parents from different species.
“The problem with Myotis bats is that there are so many species, about 130, but they all look very similar,” Foley said. “It can be very hard to distinguish them from each other, and then hybridization makes it even more difficult. If we’re trying to map out how these bats evolved so we can understand their disease immunity, being able to tell who’s who is very important.”
Untangling Hybridization
With this in mind, to create a map of the true relationships between Myotis bats, Foley and Murphy first untangled the genetic code for hybridization so they could tell more clearly which species were which.
“We collaborated with researchers from Ireland, France and Switzerland to sequence the genomes of 60 Myotis bat species,” she explained. “That allowed us to figure out which parts of the DNA represented the species’ true evolutionary history and which parts arose from hybridization.”
With that part of the puzzle solved, the researchers were finally able to examine the genetic code more closely to see how it might shed light on disease immunity.
They found that immune genes were some of those most frequently exchanged between species while swarming.
“Swarming behavior has always been a bit of a mystery for researchers,” Foley said. “Now we have a better understanding of why this particular behavior evolved — perhaps to promote hybridization, which helps spread beneficial immune gene variants more widely throughout the population.”
New Questions For Researchers
Foley and Murphy’s findings have opened the doors to new questions about the importance of hybridization in evolution.
“Hybridization played a much bigger role in our findings than we anticipated,” Foley noted. “These results have led us to wonder to what extent hybridization has obscured genomicists’ knowledge of mammalian evolutionary history, so far.
“Now, we’re hoping to identify other instances where hybridization has occurred among mammals and see what we can learn about how they are related and even how and why genomes are organized the way that they are,” she said.
By Courtney Price, Texas A&M School of Veterinary Medicine and Biomedical Sciences
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Long-eared myotis bat
A myotis bat, hunting
Myotis bats roosting together
Long-eared myotis bat
CREDIT
Dr. Nicole Foley/Texas A&M University School of Veterinary Medicine and Biomedical Sciences
Drs. Nicole Foley and William Murphy
CREDIT
Texas A&M University School of Veterinary Medicine and Biomedical Sciences
JOURNAL
Cell Genomics
ARTICLE TITLE
Karyotypic stasis and swarming influenced the evolution of viral tolerance in a species-rich bat radiation
ARTICLE PUBLICATION DATE
20-Feb-2024
Panama Canal expansion rewrites history of world’s most ecologically diverse bats
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SCIENTISTS AREN’T SURE WHAT THE EXTINCT BAT WOULD HAVE EATEN, BUT IT’S LIKELY IT HAD A SIMILAR DIET TO THE BIG-EARED WOOLLY BAT, WHICH PRIMARILY SUBSISTS ON INSECTS AND SMALL VERTEBRATES.
view moreCREDIT: FLORIDA MUSEUM PHOTO BY JERALD PINSON
Most bats patrol the night sky in search of insects. New World leaf-nosed bats take a different approach. Among the more than 200 species of leaf-nosed bats, there are those that hunt insects; drink nectar; eat fruit; munch pollen; suck blood; and prey on frogs, birds, lizards and even other bats. They’re among the world’s most ecologically diverse mammals, and until recently, it was thought they originated in South America.
“The theory that people have proposed is they got into South America early on, where their only competition was from insect-eating bats. So they evolved a bunch of different feeding strategies,” said Gary Morgan, curator of vertebrate paleontology at the New Mexico Museum of Natural History.
A new discovery suggests the story may be more complicated. In an article published by the Journal of Mammalian Evolution, Morgan and his colleagues describe the oldest-known leaf-nosed bat fossils, which were found along the banks of the Panama Canal. They’re also the oldest bat fossils from Central America, preserved 20-million years ago when Panama and the rest of North America were separated from southern landmass by a seaway at least 120 miles wide.
Based on these and other fossils, Morgan thinks previous studies may have singled out the wrong continent as the birthplace of leaf-nosed bats.
“We think they may have had a northern origin.”
Once-in-a-century opportunity leads to several new discoveries
In 2007, hundreds of engineers, excavators and geologists gathered in Panama to begin the daunting task of widening and deepening the country’s historic canal. Paleontologists weren’t far behind. After the work crews used dynamite to blow apart sections of the bank, researchers moved in, picking out fossil fragments from the rubble. The bones held clues to one of the greatest mass migrations of animals in Earth’s history, and the canal expansion marked the first time anyone had this close of a look.
About 5 million years ago, shifting tectonic plates erected a land bridge between North and South America. After more than 100 million years of separation, animals in the northern hemisphere could freely trek down south and vice versa.
“Animals like sloths and armadillos came north, while horses, tapirs, bears and elephants went south,” said study co-author Bruce MacFadden, curator of vertebrate paleontology at the Florida Museum of Natural History. The event is referred to as the Great American Biotic Interchange, and it helped shape the present-day distributions of innumerable plants and animals on the American continents.
Had the Panama Canal not been constructed, it’s likely this event would still remain a mystery to scientists.
“That showed the Panama Canal Basin, which was part of North America at the time, was full of the kind of mammals you would have found in Nebraska or Florida rather than South America,” said Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum.
Rare fossils provide clues to the origin of leaf-nosed bats
Nearly all animals found in fossil beds of similar age near the canal zone represent the southernmost range of species from higher latitudes. There were bear dogs; miniature horses rhinos; camels; early relatives of modern hippos; ungulates with paired antlers protruding from their heads and snouts; and at least one species of chalicothere, a bizarre chimeric animal that resembled a sloth crossed with a horse grafted to a giraffe.
The first mammal from South America discovered in the older beds was from a primate species, which is presumed to have rafted across the seaway.
The leaf-nosed bat is the second South American mammal found at the site. This may suggest that animals were better at crossing the oceanic barrier than previously assumed. The seaway separating North and South America was five times wider than the modern Strait of Dover between England and France and 15 times wider than the Strait of Gibraltar that divides Europe from Africa.
Yet other animals seem to have had little trouble making the journey. The list of non-mammalian animals that made their way from south to north includes a boa constrictor, a crocodile and frogs. There’s little doubt about where these organisms came from, but the fossil record of leaf-nosed bats is more ambiguous.
Today, leaf-nosed bats are distributed from South America through Arizona. Although they’ve been around for 20 million years or more, they’ve left behind surprisingly few fossils. Three extinct species in this family of similar age to the Panama specimen have been found in Colombia, and the fossils of much younger vampire bats were pulled from several sinkholes in Florida. Beyond that, there isn’t much for paleontologists to go on.
Zooming out, things become even hazier. Fossils from two closely related families that have been found in Florida predate South American leaf-nosed bat fossils and those of their relatives by 10 million years.
Further fossil discoveries will be needed to determine where leaf-nosed bats came from and why they developed such varied and refined appetites. Fortunately, there’s no shortage of fossils from the canal. Though the expansion project lasted only nine years, paleontologists collected enough material to keep them busy for the foreseeable future.
“Time was of the essence, so we collected fossils much more rapidly than we could have done the science,” Bloch said. “There are probably fossils from the project that will be described 50 years from now.”
Nicholas Czaplewski of the Oklahoma Museum of Natural History, Aldo Rincon of the Universidad del Norte and Aaron Wood of Iowa State University are also co-authors on the study.
20 million years ago, Panama was filled with a dream-like menagerie of animals that had evolved separately from their relatives in South America.
CREDIT
Florida Museum illustration by Danielle Byerley
Container vessels dramatically increased in size and number during the 20th century, and the Panama Canal had to be expanded to keep pace with the acceleration of global shipping.
CREDIT
Florida Museum photo by Jeff Gage
JOURNAL
Journal of Mammalian Evolution
ARTICLE TITLE
A new early Miocene bat (Chiroptera: Phyllostomidae) from Panama confirms middle Cenozoic chiropteran dispersal between the Americas
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