Arion subfuscusFLICKR, WWW.BAYERCROPSCIENCE.CO.UKSome parasites manipulate their hosts to behave in ways that help spread the invaders to new environments or hosts. A study published online last month (February 27) in Behavioral Processes reports that the parasitic nematode Phasmarhabditis hermaphrodita infects slugs and directs them toward more parasites. The researchers found they could reproduce this behavior by increasing the slugs’ serotonin levels, indicating that the parasites might be using the same mechanism.
Just why the parasite might influence its host to pick up more parasites is unclear, making some researchers question if P. hermaphrodita is indeed manipulating its host’s behavior. “What the authors need to show is that there is a direct advantage to the parasites inside the host when the slug behavior changes,” Edwin Lewis, professor of nematology at the University of Idaho, writes to The Scientist in an email. “This is really difficult to show.”
In parasitizing slugs, P. hermaphrodita kills its hosts. It waits in the soil and penetrates passing slugs, which die within days or weeks. More nematodes emerge to feast and breed on the dead slug before they disperse into the soil.
In Europe, the nematode is used by farmers and gardeners ...
