Wednesday, October 16, 2013

Paleo pest

While just a fraction of the size of the giant dragonflies that flew in the Carboniferous period 300 million years ago, the tiny Eocene mosquito above is in some ways more important and in its preservation much more improbable. Smithsonian researcher Dale Greenwalt realized the rarity of the specimen, which had been discovered in oil shale in western Montana, after it was given as a gift to the National Museum of Natural History in Washington, D.C. The contents of the mosquito's stomach are full of the blood of animals that lived 45 million years ago, as proven by the high levels of iron ions and molecules of heme, which carry hemoglobin. Which species it preyed upon will remain unknown, since DNA molecules are too complex and fragile to fossilize (which is what also rules out cloning). The unlikely events that resulted in the first fossil of a mosquito found still engorged with ancient blood would have played out as follows: “The insect had to take a blood meal, be blown to the water’s surface, and sink to the bottom of a pond or similar lacustrine [lake-like] structure to be quickly embedded in fine anaerobic sediment, all without disruption of its fragile distended blood-filled abdomen.”

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