Thursday, July 24, 2008

More Proof that Parasites Rule the World

This week's Nature has an article by Kuris et al. [1] that presents the results of a long-term study of a California estuary that quantified biomass of various groups of organisms. Although as a percentage of the total, parasites are only about 1% of the animal biomass, but it turns out that parasitic trematodes can reach biomasses greater than the birds and fishes in the ecosystem! Some of these parasites are host castrators, thus if one considers these hosts as extended phenotypes of the parasites, the effective biomass of parasites is even higher. One of the things that I found most interesting, though, is that in some snails, the trematode parasites can be 22% of the animal' soft-tissue body weight, a stat published by several members of the same group this year [2]. There has already been a much-hyped instance of researchers accidentally sequencing a gene from a trematode parasite instead of that of the frog they were working on. Now these data are a big caution that the potential for sequencing parasite instead of host can be very high in many invertebrates. Potential for parasite contamination might be very high in EST libraries made from organisms that might be hosts, too...yikes!!

1. Kuris, A.M., R. F. Hechinger, J. C. Shaw et al. 2008. Ecosystem energetic implications of parasite and free-living biomass in three estuaries. Nature 454:515-518.
2. Hechinger, R.F., K. D. Lafferty, F. T. Mancini III, R. R. Warner, and A. M. Kuris. 2008. How large is the hand in the puppet? Ecological and evolutionary factors affecting body mass of 15 trematode parasitic castrators in their snail host. Evolutionary Ecology, in press.

Photo credit: Rodrigo Mexas, on

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