Trematode and Flatworm: Mean, Parasitic, and Mobile

Just to be contrary, or perhaps for another reason, parasitic flatworms are one of the few exceptions to the global rule that species are most diverse in warm climates.

That is, for a marine horn snail, the chance of being attacked and castrated by a flatworm increases greatly the farther the snail is from the tropics, as a Smithsonian Tropical Research Institute team reported recently in the journal Ecology. 

The team was able to look at the habits of trematode flatworms and other parasites by keeping an eye on their hosts, horned snails, which live on coasts from the tropics to the temperate zones. "It lets us do a real, apples-to-apples comparison when the habitat--the snails--is the same across this broad geographic region," said Mark Torchin, a lead scientist at the Smithsonian, in a release. 

Researchers collected both snails and parasites from 43 field sites in five countries and 27 degrees of latitude in both the Pacific and Atlantic oceans. Because parasite prevalence, diversity and competition rates increased with higher latitude in a reversed diversity range, they believe that local ecological factors play a part in shaping biodiversity, according to the release.

For instance, snails might die in larger numbers in the tropics, because of hurricanes, storm runoff, and other forms of environmental instability. In that case, trematodes would have fewer victims to parasitize. The fact that more snails live somewhat longer lives in the temperate zone might mean better picking for the trematodes, as the release said.

Next, the researchers will test their findings in Asia.

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