Plasticity of grooming behavior against entomopathogenic fungus Metarhizium anisopliae in the ant Lasius japonicus
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Social insects employ many types of defense mechanisms against parasites and pathogens because they face high risks from infections due to crowded living conditions with closely related nestmates. Grooming behavior, including self-grooming and allogrooming, can remove fungal spores on the cuticles of social insects and may be a behavioral defense mechanism to improve survivorship. Allogrooming between nestmates has been predicted to be especially important as a defense against ectoparasites. However, little is known about the plasticity of grooming behavior in susceptible environments. Here, we show that the ant Lasius japonicus increases the frequency of allogrooming rather than self-grooming to improve survivorship against the entomopathogenic fungus Metarhizium anisopliae. We found that increasing fungal dosage and ant group size influenced the plasticity of grooming behavior. Additionally, the survival rate of the ants over 30 days improved with increased group size. Our results suggest that social insects opt for altruistic behavior to prevent the spread of diseases. This study illustrates how ants maintain colonies through grooming behavior in the presence of fungal spores.
KeywordsSelf-grooming Allogrooming Behavioral defence mechanism Group size Fungal dosage Survivorship
We thank Dr. Takayoshi Nishida and members of our laboratory for helpful comments and critical remarks on an early draft of the manuscript. The paper was improved by the comments of Dr. Kenji Matsuura. This work was supported in part by the 21st century COE program for Innovative Food and Environmental Studies Pioneered by Entomomimetic Sciences from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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