Zombie ant fungi manipulate hosts to die on the 'doorstep' of the colony

http://www.eurekalert.org/pub_releases/2014-08/ps-zaf081814.php

PUBLIC RELEASE DATE: 18-Aug-2014

Contact: A'ndrea Elyse Messer
Penn State
Zombie ant fungi manipulate hosts to die on the 'doorstep' of the colony

A parasitic fungus that must kill its ant hosts outside their nest to reproduce and transmit their infection, manipulates its victims to die in the vicinity of the colony, ensuring a constant supply of potential new hosts, according to researchers at Penn State and colleagues at Brazil's Federal University of Vicosa.

Previous research shows that Ophiocordyceps camponoti-rufipedis, known as the "zombie ant fungus," controls the behavior of carpenter ant workers -- Camponotus rufipes -- to die with precision attached to leaves in the understory of tropical forests, noted study lead author Raquel Loreto, doctoral candidate in entomology, Penn State's College of Agricultural Sciences.

"After climbing vegetation and biting the veins or margins on the underside of leaves, infected ants die, remaining attached to the leaf postmortem, where they serve as a platform for fungal growth," Loreto said.

The fungus grows a stalk, called the stroma, which protrudes from the ant cadaver. A large round structure, known as the ascoma, forms on the stroma. Infectious spores then develop in the ascoma and are discharged onto the forest floor below, where they can infect foraging ants from the colony.

This fungal reproductive activity must take place outside the ant colony, in part because of the ants' social immunity, which is collective action taken to limit disease spread, explained study co-author David Hughes, assistant professor of entomology and biology, Penn State.

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