Wednesday, May 16, 2007

Positive Parasites?

Recent research has discovered that parasites can evolve fairly quickly to become helpful instead of harmful. Parasites have long been famed to be harmful to their hosts with some harmful enough to even kill their host. In the case of a parasite known as Wolbachia, present in nearly one fifth of all insects, harmful affects are typically in making females less fertile; but scientists have now discovered that Wolbachia can boost female/host fertility instead of lessen it in order to spread themselves in nature. Insects can only get Wolbachia from their mothers and additional effects from this bacteria include, turning males to females, causing infected females to reproduce without males and triggering vicious cycles of increasing female promiscuity and male sexual exhaustion. The presence of these parasites also often carries a toll on their victims, for instance, cutting down the number of eggs that females produce. Despite these effects, researchers have found that in span of just 20 years, this bacteria has evolved means of boosting offspring production to better spread itself in a laboratory setting by 10%. Initially a 20% decline in offspring production was observed.
But what about the idea of a positive parasite?

It is still unknown how Wolbachia lead to a boost in fertility, but experts suggest it is due to a nutritional benefit. In that rapid evolutionary span, Wolbachia have been concluded to be heading in the direction of being needed for host survival. This developing mutually beneficial relationship has been compared to the symbiotic relationship of mitochondria within cells. Wasps for example need Wolbachia to generate eggs in order to reproduce. This research sheds light on the symbiotic theory and shows that a dependant relationship between host and parasite can evolve in a very short time span.

--contributed by Stephen Rettig



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