zq28 (zygote quarterly)

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ZQ28

The Latest Buzz Tom McKeag

there seems to be a continually escalating (albeit evolutionarily slow) arms race on the insect front and quite a few organisms have achieved an uneasy parity with their flying antagonists. Mosquitoes belong to the Order Diptera, the True Flies, and the family Culicidae. Their name means “little fly” in Spanish. There are over 3,500 known species and they have been on earth for at least 100 million years. Like many other insects, mosquitoes begin their life as aquatic larvae, going through four molting stages or instars as larvae, emerging from single or multi-cell “rafts” of eggs laid on the surface of water. During these larval stages they feed on algae, plankton, fungi and bacteria and other microorganisms. They do not have gills during this phase, so must rise to the surface frequently for oxygen. At this small scale, the surface tension of water is a major challenge, so mosquitoes have evolved a siphon to pierce through the clinging water molecules - a micro snorkel! Some species have even adapted to piercing the walls of aquatic plants to take advantage of the oxygen found in them. After as much as a fortnight of larval feeding and growth, the mosquito enters the pupa stage within a floating case where the final transformation to adult occurs. Male mosquitoes will live an average of about a week, and females

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average about six weeks, although lifespans vary widely across species and environments. Both sexes will feed on nectar, aphid honeydew and plant juices, with the females searching out both cold and warm blooded animals, even other invertebrates, for a protein supply. Different mosquitoes have different patterns of activity; the Asian Tiger, for instance, is known for aggressive daytime feeding, while many others come out only at dusk. I suppose we humans would not care so much about studying this creature if it wasn’t for the dangerous microbial hitchhikers inside of her. Three types are of especially serious concern. The Anopheles mosquito carries the Plasmodium (falciparum or vivax) protozoan parasite that causes malaria. Two types of Aedes mosquito, the Asian Tiger (albopictus) and the Egyptian (aegypti) carry the three viruses of Zika, Dengue Fever, and Chikungunya. In addition, various other genus of mosquito carry several encephalitis viruses of grave concern to humans and livestock. A vector is an agent that carries and transmits a pathogen from one organism to another. The mosquito is the world’s master vector, as it “mainlines” a parasite or virus, perhaps picked up from passerine birds, directly into a mammalian host’s bloodstream.