A Plea For Parasites

TICK iStock 000010660597XSmall 300x267 A Plea For Parasites“Parasite” shouldn’t be a dirty word. That’s the plea from two biologist who find that conservation textbooks largely ignore one of Earth’s most common – and influential – life forms.

Word experts say we can thank the Medieval French for coining “parasite,” which – roughly translated – means “one who eats from another’s table.” Today, biologists have sliced and diced parasitism into a slew of symbiotic life strategies that all rest on the parasite’s close relationship with a host. “Obligate parasites” like some ants and plants, for instance, can’t live without their host. “Brood parasites,” like cuckoos and cowbirds, drop their eggs in the nests of other birds. The microbes that cause malaria and Lyme disease need a host mosquito or tick to move around and complete their life cycles.

No matter how they survive, “parasites are dominant and diverse,” note Elizabeth Nichols of the American Museum of Natural History (AMNH) and Columbia University in New York City and Andrés Gómez of AMNH. Some studies suggest that “parasites outnumber free-living biodiversity by as much as 50%,” they note in Biological Conservation. At least 76,000 parasitic species, for instance, inhabit nearly 45,000 vertebrate hosts.

The problem? “They receive scant positive attention from conservation scientists and educators,” the pair writes. When they surveyed 77 English-language conservation biology textbooks published between 1970 and 2009, for instance, they found that “the vast majority” — 72% — portrayed parasites “uniquely as threats to conservation goals… or do not mention parasites at all.” What’s missing is “the importance of parasite biodiversity as fundamental components of ecosystems, and in some cases, as conservation targets in their own right.”

Parasites, for instance, can play an important role in determining how abundant a species is – or even where it lives. One shrimp parasite, for example, splits populations into groups that live near the surface and deeper down. And parasites “stand to be among the biggest losers” when host species go extinct. Aside from a few calls for their conservation, however, “parasite biodiversity is still portrayed by much of the scientific community with a mixture of disregard, open antipathy and lack of awareness.”

To build a more pro-parasite world, they say textbooks need to include five basic messages. “That parasites:

(1) are diverse, and represent the majority of all life in the planet;

(2) are crucial players in ecological and evolutionary processes;

(3) present challenges to conservation practice through their roles in population declines;

(4) deserve the same consideration to intrinsic, aesthetic and utilitarian value as their free-living hosts; and finally

(5) are seldom targets of conservation action.”

Parasite conservation, they conclude, “represents a series of both opportunities and challenges.” David Malakoff | December 14, 2010

Source: Nichols, E., & Gómez, A. (2010). Conservation education needs more parasites. Biological Conservation DOI: 10.1016/j.biocon.2010.10.025

Image © Oliver Sun Kim

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