Web Extra  Friday, October 18

Dinosaurs were bugged too

Two articles published in September are providing tools for possibly eradicating one of the worst diseases in history: malaria. The Sept. 26 Nature publishes the genome sequence of the malaria parasite, Plasmodium falciparum. And an article in the Sept. 27 Science publishes the genome of the parasite's carrier, the mosquito Anopheles gambiae. Modern technologies are giving us new information about these disease carriers. But paleontologists know that mosquitoes have likely been a scourge of many animals for millions of years.

The earliest reported mosquito, one discovered by American Museum of Natural History researchers in Burmese amber from the Cretaceous, has what appear to be the remnants of its last meal -- a blood meal -- in its gut.

The Burma discovery, published in the American Museum Novitiates last March, dates to about 100 million years ago. It is one of two mosquito specimens from the Cretaceous -- the other being from Canadian amber dated to about 70 million years ago. The two specimens suggest that mosquitoes originated in the lower Cretaceous-upper Jurassic, says Paul Nascimbene of the American Museum of Natural History.

Mosquitoes are members of the order Diptera, or flies, and they come from a particularly annoying group, the Culicomorpha, which includes other bloodsuckers such as black flies and biting midges. According to Nascimbene, a specimen of what researchers believe to be a biting midge with mouth parts big enough to puncture a dinosaur's skin was discovered in a Cretaceous amber deposit in New Jersey.

The results of molecular analyses in the last few years appear to agree. For example, a study published in Systematic Biology last year indicates that the Anopheline line -- which includes Anopheles, the carrier of malaria -- probably originated more than 95 million years ago in what was western Gondwanaland, the southern supercontinent that included South America and Africa. Anophelines probably spread to the northern land masses during the Cenozoic.

Mosquitoes carry some of the world's deadliest diseases, including several virus disorders (yellow fever, dengue fever, West Nile virus, eastern and western equine encephalitis, St. Louis encephalitis, Japanese encephalitis), filariasis (a disease caused by tiny parasitic worms) and malaria. Mosquitoes also serve as carriers for heartworms, a common disease of domestic dogs.

Dave Lawrence
Geotimes contributing writer

This page was updated Oct. 24, 2002

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