Rare Blood-Engorged Mosquito Fossil Found
The fossil of a blood-engorged mosquito was found in northwestern Montana.
Sept. 15, 2011 --
A stunning array of prehistoric feathers, including dinosaur protofeathers, has been discovered in Late Cretaceous amber from Canada. The 78 to 79-million-year-old amber preserved the feathers in vivid detail, including some of their diverse colors. The collection, published in this week's Science, is among the first to reveal all major evolutionary stages of feather development in non-avian dinosaurs and birds. In this slide, an isolated barb from a vaned feather is visible trapped within a tangled mass of spider's web.
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"These specimens were most likely blown into the tacky resin, or were plucked from an animal as it brushed against resin on a tree trunk," lead author Ryan McKellar told Discovery News. "The fact that we have found some specimens trapped within spider webs in the amber would suggest that wind played an important role in bringing the feathers into contact with the resin," added McKellar, a postdoctoral fellow at the University of Alberta's Department of Earth and Atmospheric Sciences. The feather filaments shown here are similar to protofeathers that have been associated with some dinosaur skeletons.
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McKellar and his team made the discovery after screening over 4,000 amber samples from Grassy Lake, Alberta. The amber, collected by the Leuck family, is now housed at the Royal Tyrrell Museum. The researchers ruled out that the inclusions were mammal hairs, plant or fungal remains based on their structure. Some dinosaur fossils retain skin impressions, so the scientists could match dinosaur protofeathers (hair-like projections) to some of the objects within the amber. Here, a feather is visible near a plant bug. The high number of coils in the this feather suggests it could have come from a water-diving bird.
The translucent tree resin provides a window into feather evolution, from non-avian dinosaurs to birds. "Part of what makes this particular set of feathers interesting is that we find the very simple Stage I and II feathers alongside advanced feathers that are very similar to those of modern birds, Stages IV and V," McKellar said. The researchers aren't yet certain why feathers first evolved, but the density of the protofeathers suggests that they helped dinosaurs with regulating temperature. Dinosaurs such as Troodon or Deinonychus may have produced the feathers. The cork-screw shaped structures in this slide are the tightly coiled bases of feather barbules.
As feathers continued to change, they developed tufts, barbs, branching features, little hooks, and more. Some of the most advanced feathers in the collection are comparable to those of modern grebes. They appear to help diving, indicating that some of the prehistoric birds were divers. McKellar suspects the marine birds might have been Hesperornithiformes, a specialized flightless diving bird from the Dinosaur Era. This is a white belly feather of a modern grebe, showing coiled bases comparable to those seen in the Cretaceous specimen.
Some of the feathers appear transparent now, but would have been white in life. A range of colors for the feathers is evident, though, with grays, reds and various shades of brown preserved. This, and prior research, suggests that non-avian dinosaurs and prehistoric birds could be quite flashy. The pigment within this fossilized feather suggests it would have originally been medium- or dark-brown in color.
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In an accompanying "Perspectives" article in Science, Mark Norell points out that the dinosaur Sinosauropteryx is thought to have had a reddish banded tail, while Anchiornis likely possessed a striking black body, banded wings and a reddish head comb. Norell, chair and curator of the American Museum of Natural History's Division of Paleontology, told Discovery News that the newly discovered feathers are "very exciting." Here, a feather barb within Late Cretaceous Canadian amber shows some indication of original coloration.
Some dino aficionados have wondered if DNA could be extracted from the feathers. "Almost anything is possible," Norell said, quickly adding that most DNA-extraction studies have been conducted on much younger amber, dating to around 20-30 million years ago, and even those led to questionable results. "Maybe bits and pieces could be identified, but not the whole genome." Shown are 16 clumped feathers in Late Cretaceous amber.
People with amber objects, such as jewelry, also probably don't have prehistoric feather inclusions, since such items are extremely rare and dealers isolate the best pieces. Nevertheless, McKellar said, "There is some hope that you could have small feather fragments that have been overlooked." An unpigmented feather and a mite in Canadian Late Cretaceous amber.
About 46 million years ago, a mosquito sunk its proboscis into some animal, perhaps a bird or a mammal, and filled up on a meal of blood. Then its luck turned for the worse, as it fell into a lake and sunk to the bottom.
Normally this wouldn't be newsworthy, and nobody would likely know or care about a long-dead insect in what is now northwest Montana. But somehow, the mosquito didn't immediately decompose — a fortuitous turn of events for modern-day scientists — and became fossilized over the course of many years, said Dale Greenwalt, a researcher at the National Museum of Natural History in Washington, D.C. Greenwalt discovered the mosquito fossil after it was given to the museum as a gift, and he immediately realized the specimen's rarity.
It is, in fact, the only blood-engorged mosquito fossil found, Greenwalt told LiveScience. The fossil is even stranger because it comes from shale, a type of rock formed from sediments deposited at the bottom of bodies of water, as opposed to amber, the age-old remains of dried tree sap, in which insect remnants are generally better preserved. (See Photos of Ancient Life Trapped in Amber)
"The chances that such an insect would be preserved in shale is almost infinitesimally small," Greenwalt said.
In their study, Greenwalt and his collaborators bombarded the mosquito fossil with molecules of bismuth, a heavy metal, which vaporizes chemicals found in the fossil. These airborne chemicals are then analyzed by a mass spectrometer, a machine that can identify chemicals based on their atomic weights, Greenwalt said. The beauty of this technique, called time-of-flight secondary ion mass spectrometry, is that it doesn't destroy the sample — previously, similar techniques required grinding up portions of fossils, he added. The analysis revealed hidden porphyrins, organic compounds found in hemoglobin, the oxygen-carrying protein in blood, hidden in the fossilized mosquito's abdomen.
The finding may bring to mind the story of "Jurassic Park," a novel and movie in which scientists resurrect dinosaurs from DNA preserved in blood-engorged mosquitoes preserved in amber. Although this finding doesn't really make this fictitious story any more likely, it does show that complex organic molecules besides DNA can be preserved for a long time, Greenwalt said.
The discovery also shows that "blood-filled mosquitoes were already feeding at that time, suggesting that they were around much earlier and could have fed on dinosaurs," said George Poinar, a paleo-entomologist at Oregon State University, who wasn't involved in the research.
Greenwalt said he had no way of knowing exactly how the mosquito was preserved so well. Perhaps the most likely hypothesis is that the insect was trapped in a covering of water-suspended algae, which are capable of coating specimens in a sticky, gluelike material, before sinking to the bottom; this algae process has been shown to fossilize other types of insects, he said.
Researchers don't know what kind of animal the blood came from, since hemoglobin-derived porphyrins amongst different animals appear to be identical, Greenwalt said.
The study is exciting, because it provide more evidence that porphyrins, organic compounds found in "virtually all living organisms from microbes to humans in varying amounts" are "extremely stable" — and are thus a perfect target for studying long-dead plants and animals, said Mary Schweitzer, a researcher at the North Carolina Museum of Natural Sciences, who wasn't involved in the study.
Email Douglas Main or follow him on Twitter or Google+. Follow us @livescience, Facebook or Google+. Article originally on LiveScience.
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