D3174: Potential mechanisms explaining how trematode parasites manipulate the behavior of its ant hosts

Many species of arthropods are hosts to many species of parasites, and in many situations transmission between hosts is helped by behavior changes in the arthropod. An iconic example is the trematode, Dicrocoelium dendentricum, which uses ants as its second intermediate host. Infected ants exhibit an unusual temperature dependent behavior: they use their mandibles to fix themselves firmly on the top of the flower every evening, where they stay overnight, returning to foraging in the morning as the day warms. This behavior facilitates the transmission of the parasite into the definitive ruminant hosts. During the manipulation, ants do not forage, do not defend themselves from predators, and do not perform typical worker duties for their queens. The larvae parasites are mostly encyst in the ant gasters, except for one larva sits by the subesophageal ganglion (SEG), a cluster of nerve cells, in ant brains. It is widely considered that the behavioral change in infected ants is caused by the SEG-associated larva. The observed phenotypic changes are multifaceted: cramping of the mandibular muscles, foraging, predator avoidance, and others. However, the molecular mechanisms underlying the behavioral change remain unknown. In this infographic, we present eleven mechanisms potentially involved in this parasite-host interaction, including: circadian rhythm, insect chill comma, and non-social Hymenoptera inactive nighttime behavior. For each, we present examples from other arthropod-parasite systems.