Experimental infection of the ant Polyrhachis furcata with Ophiocordyceps reveals specificity of behavioural manipulation

Abstract

Recent studies revealed that fungi of the Ophiocordyceps unilateralis sensu lato complex are highly host specific. Infected ants leave their colony, wander singly with convulsions and eventually bite firmly vegetal substrates in the low vegetation and maintain this position until death. Subsequently, a fungal stroma grows from the back of the ant's head and produces spores. We experimentally infected Polyrhachis furcate ants by injecting them with suspensions of blastospores from three closely related fungi of the O. unilateralis species complex: Ophiocordyceps polyrhachis-furcata, Ophiocordyceps camponoti-leonardi and Ophiocordyceps camponoti-saundersi, pathogens isolated from the ant species P. furcata, Colobopsis leonardi and Colobopsis saundersi. We monitored the survival and behaviour of ants for 30 d after blastospore injection and compared the results with negative controls. Our results showed that the number of dead ants on the floor did not show significant differences across treatments. However, the typical erratic wandering behaviour and death grip display were observed only when ants were infected by their specific parasite, 0. polyrhachis-furcata. Experimental ants initiated death grip between 13 and 17 d after infection, and stayed locked in the position. We suggest that the inability of Ophiocordyceps fungi to manipulate the behaviour of non-host ant species might be responsible for the observed specificity. (C) 2018 Elsevier Ltd and British Mycological Society. All rights reserved.