““What would happen if the parasites were removed from this picture? Would there be fewer birds in the sky, more fish in the sea? Lafferty doesn’t know, but the change would almost certainly have a domino-like effect on the food chain. In some fragile ecosystems where animals struggle to get by on scarce resources, manipulative parasites might even tip the balance toward the survival or extinction of a species. Lafferty recounted joining Japanese biologists who were studying a type of endangered trout in hopes of increasing its numbers. In the fall, the team noticed, the fish were unusually well nourished; their bellies were packed full of crickets. What had made this source of nutrients suddenly so plentiful? A hairworm closely related to the species Thomas has long been studying was sending droves of the crickets into the water in late summer. If it weren’t for the parasite, said Lafferty, it’s possible the trout might already be extinct.””
