First, it turns the brown crustaceans, which resemble shrimp the size of black beans, bright orange through a chemical reaction. The orange exoskeleton is \u201clike a neon sign that says, \u2018Eat me!\u2019\u201d says David Samuel Johnson, a marine ecologist at the Virginia Institute of Marine Science. Then, the parasite changes the amphipod\u2019s behavior, likely by affecting its sensitivity to light. With its instincts scrambled, an infected marsh hopper will stumble out of cover and into the danger zone, \u201clike a drunk who wanders into traffic,\u201d says Johnson, where a hungry bird is likely to spot it.<\/p>\n
\u201cThey\u2019re not aware the danger is there,\u201d he adds.<\/p>\n
Zombies are surprisingly common in nature. There\u2019s a parasitic fungus<\/a>, for instance, that causes an ant to march away from its colony, climb a leaf or blade of grass, clamp onto the end, and then die so its dangling body can rain spores onto other potential victims. There\u2019s a parasitic larva of a wasp<\/a> that manipulates its spider host to turn its web into a cocoon. And in Japan, a nematomorph parasite sends crickets<\/a> and grasshoppers on suicide missions, causing them to leap into the water where hungry trout lurk. The list goes on<\/a>\u2014each an example of the intricate ways parasites manipulate their hosts to complete their own reproductive life cycles.<\/p>\n Yet there\u2019s something different about the parasite surge in the Plum Island Estuary: it was caused by scientists.<\/p>\n For more than a decade, researchers with the TIDE Project<\/a> have used the estuary as a large-scale experimental site. To mimic the effects of sewage and agricultural runoff, they dumped fertilizer into marsh tidal creeks and have been studying the consequences on the ecosystem.<\/p>\n
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