A Quick Getaway
Parasites need to find food and shelter, but their other big challenge in life is transmission - getting out of their current host and into a new victim - a speedy getaway is a crucial step for any thief. Many parasites manipulate host behaviour in order to help with transmission, such as trematode worms, which influence their host in order to make them more conspicuous to predators. Infected Killifish (Fundulus parvipinnis) come to the surface and swim in circles, jerking wildly in order to attract the attention of hungry shorebirds, the second host in the complex lifecycle of the trematode worm. Similarly, when gammarus crustaceans (Gammarus pulex) are infected with the parasitic worm Pomphorhynchus laevis, they give up their normally cautious behaviour and become daredevils. They swim towards the light and are eaten by fish such as the three-spined stickleback (Gasterosteus aculeatus), the next host for the parasite