A miniature zombie apocalypse: how one fungus controls the minds and bodies of ants to send them to their demise (Mott, 2021)

notes/quotes

“A single spore enters the body of an ant. It grows into a mass of fibers that take control of the antʼs mind and body. The ant is forced to climb a nearby tree before locking its jaws and holding on to what will be its final resting place. Where the ant has ventured is perfect for the fungus. The temperature, humidity, air flow, they are all perfect. The fungus continues to grow, slowly consuming the innocent insect. A powerful stalk pierces through the antʼs exoskeleton using huge amounts of pressure and a spore capsule grows. The capsule erupts, shedding thousands of spores onto more unsuspecting ants.”^[1]

• this fungi is a parasitoid; it’s life cycle is built around (requires) the ant’s death.^[1:1]

• parasitoids are “somewhere between” parasites and predators.^[1:2]

“Just like a parasite, [parasitoids] infect their host and use them for nutrients to grow; but they also kill their host as a necessary part of their life cycle”^[1:3]

• these parasitic fungi aren’t the only parasitoids—many parasitic wasps are “more well known” for this behaviour.^[1:4]

• Hyposoter horticola (wasp species) preys on caterpillars:

“A female H. horticola seeks out freshly laid butterfly eggs and waits for just the right moment to strike. Just when a young caterpillar is about to emerge from its egg, she lays her own eggs inside the developing larvaʼs body. The wasp larvae remain in the caterpillarʼs body until it is almost fully grown. Then, shortly before the host would have spun itʼs cocoon, the wasp larvae rapidly grow, consuming the entire contents of the hostʼs body before emerging and spinning their own cocoons on its corpse where they mature into adult wasps.”^[1:5]

• Ophiocordyceps unilateralis (“one of the mulitple ant-zombifying species”^[1:6]) infects and kills host ants.^[1:7]

“All the dead ants were found ‘under leaves, attached by their mandibles, on the northern side of saplings ∼25 cm above the soil, where temperature and humidity conditions were optimal’ for the growth of this particular fungal species.”^[1:8]

• for the infected ants to be engaging in such “exact behavior”, what the fungus is doing to the ants’ minds/bodies must “be very complex indeed.”^[1:9]

“It has been found that the fungal cells invade ant muscle fibers but donʼt attack the brain. To control the antʼs behavior, O. unilateralis instead infects the body and comes right up close to the brain where it may secrete chemicals that alter brain function and behavior.”^[1:10]

related reading

• Andersen et al. ‘The Life of a Dead Ant: The Expression of an Adaptive Extended Phenotype’. The American Naturalist 174, no. 3 (September 2009), pp. 424-433. doi:10.1086/603640.