Home National museum A Last Meal for the Ages | Smithsonian Voices

A Last Meal for the Ages | Smithsonian Voices

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Mosquito fossils from northwestern Montana, such as the recently described species Culisteta kishenehn shown here, reveal that mosquitoes have changed remarkably little over the past 46 million years.
Dale Greenwalt

The National Museum of Natural History is emblematic for its superb prehistoric pieces such as the Nation’s T. rex, the colossal skeleton of Diplodocus or the gaping maw of Megalodon. But one of the museum’s most remarkable fossilized treasures is only a few centimeters long. Just looking at it might make you want to scratch your skin or grab a fly swatter.

The fossil in question is a petrified mosquito imprinted on a slab of shale and displayed under a magnifying glass in the museum hall Wonder Items exposure. Compared to its exhibit companions, which include treasures from the the vast collection of the museum like Marthe, the last passenger pigeon, mammoth fat chunks and original hand-colored illustrations of the legendary John James Audubon birds of americathe mosquito appears quietly banal.

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One of the most remarkable fossils in the museum – a 46 million year old mosquito with a dark patch of fossilized blood preserved in its abdomen.

Smithsonian Institution

However, a closer look at his guts reveals something remarkable. Stained inside its abdomen, which appears to have been filled with a sharpie, are the remnants of the blood the mosquito washed away 46 million years ago. When it was described by Smithsonian scientists in 2013, it was the first known preserved mosquito fossil with a bloody belly. For world mosquito day on August 20, we thought it was time to shine a light on this groundbreaking fossil.

This discovery seems straight out of Jurassic Park, where scientists are harvesting “Dino DNA” from blood-gorged mosquitoes entombed in chunks of amber. For decades, the very idea of ​​blood fossilization seemed to belong strictly to the realm of science fiction. That is why Dale Greenwalt, a research associate in the museum’s department of paleobiology, knew he might have stumbled upon something special when he first placed the mosquito fossil under the microscope. “I immediately saw the enlarged and darkened abdomen and wondered, ‘Could this be a blood-engorged mosquito?'”

The mosquito fossil is from a stretch of the Flathead River in Montana’s Glacier National Park. While the area is now renowned for its fly fishing, Greenwalt has ventured there for fifteen years, angling a rich assortment of old flies instead.

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The banks of the Flathead River in northwest Montana are covered in slabs of shale that preserve a rich assortment of fossil insects like wasps, beetles, water bugs, and a multitude of mosquitoes.

Dale Greenwalt

Although this region is now a rugged expanse of prairie and snow-capped mountains, it was a humid mosaic of subtropical forests and wetlands mirroring the Florida Everglades in Eocene times 46 million years ago. With lots of water and heat, this area was a paradise for mosquitoes. Greenwalt discovered several new mosquito species in paper-thin Eocene shale Kishenehn formation which borders the river. Many of these ancient bloodsuckers look almost identical to the mosquitoes buzzing around today.

While the site is iconic for its preservation of tiny insects – intricate features like wing veins, antennae and even color are carved into the rock – fossilized blood this ancient would be a first. So Greenwalt took the dark-bellied mosquito to Tim Rosethe director of the museum’s analytical labs who helps scientists examine everything from ancient artifacts to large chunks of asteroids with heavy-duty scanning electron microscopes.

With the delicate fossil under the scanning microscope, Rose recorded how X-rays were deflected from different parts of the fossil to decipher the molecular makeup. He was specifically looking for which parts of the mosquito contained iron, a key component of red blood cells. “If we have residual blood, there should be higher iron content in the abdomen than in any other part of the mosquito,” Rose said.

X-rays confirmed a spike of iron molecules in the mosquito’s blackened belly. Further tests of the abdomen revealed remnants of hemoglobin, the molecules that give blood its characteristic purple color. “Insects don’t make hemoglobin — it had to come from the mosquito host,” Greenwalt said. They had taken fossilized blood.

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Smithsonian paleontologist Dale Greenwalt holds the slab of shale containing the first blood-engorged fossilized mosquito ever described.

James DiLoreto

News of their discovery made headlines around the world. “The Jurassic Park connection secured great publicity,” Greenwalt recalls. However, anyone hoping to revamp dinosaurs like T. rex with this mosquito may be a little disappointed. First, the blood is 20 million years too young to come from any of the non-avian dinosaurs that terrorized park visitors on the big screen. There is also no way of knowing what animal blood the mosquito drank before it died. Finally, 46 million years weighed on the quality of the sample, according to Rose. “Only a fragment of blood was found,” Rose said. “There’s no DNA, so you can’t get too excited about that possibility.”

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The oldest known blood-fed mosquito specimen in the world is of outsized scientific importance despite its small size.

Jack Tamisiea

Greenwalt argues that this makes the fossil no less remarkable. “This preservation is one ‘in a million’ occurrence and is due to the ancient lake’s unique preservation environment,” Greenwald said. All the blood sloshing around inside his abdomen would have caused him to swell like a balloon, making the mosquito incredibly fragile. Even the slightest pressure could cause this blood balloon to burst. Yet the insect fell into the water where it was encased in a sticky algae bloom, sank to the bottom of the pond uncaught by a hungry fish, and was buried with its swollen stomach intact.

Over the years, Greenwalt has collected about 8,000 insect specimens in northwestern Montana, including a few well-fed mosquitoes. “We keep finding new blood-engorged mosquito specimens, many of which are much better preserved than the original,” Greenwalt said. They remain “the only fossil blood-fed mosquitoes known to science”.

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