Manipulation of host behaviour by parasites

Abstract

The lancet fluke Dicrocoelium dendriticum uses herbivores as final hosts, while snails and ants act as intermediate hosts. The genetically identical parasite larvae within an ant achieve the host change from ant to herbivore through a division of labour: A larva that does not develop further invades the brain of the ant and forces its host to expose itself on plants during the cool night hours. If an infected ant is accidentally eaten by a herbivore, the clone siblings in the abdomen of the ant invade the liver of its definitive host, the herbivore, and reach sexual maturity. The sacrifice of the brainworm is explained by kin selection. The induced behavioural change requires still unknown mechanisms of communication within the parasite clone and with the host. The complex life cycle of the lancet fluke is linked to dry grassland biotopes, which are worth protecting for their biodiversity. Preserving such habitats could also save the lancet fluke from extinction.