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Putting the Waste Out: A Proposed Mechanism for Transmission of the Mycoparasite Escovopsis Between Leafcutter Ant Colonies

Summary

This research reveals how a parasitic fungus spreads between leaf-cutting ant colonies through their waste management systems. The fungus produces specially adapted spores that can remain dormant until reaching new ant colonies, attaching to passing ants as a means of transport. This discovery helps us understand the complex relationships between ants, their fungal food source, and parasites that threaten their colonies. Impacts on everyday life: – Provides insights into managing agricultural pests and diseases – Demonstrates how waste management affects disease spread in social systems – Shows how parasites evolve sophisticated strategies to reach new hosts – Highlights the importance of proper waste disposal in controlling infections – Reveals nature’s complex solutions to survival challenges

Background

The attine ant system is a remarkable example of symbiosis where leaf-cutting ants tend their domesticated fungus Leucoagaricus, which has been their main food source for 8-12 million years. This mutualism is exploited by the fungal parasite Escovopsis, which poses a direct threat to ant colony fitness. Despite research on Escovopsis biology, the mechanism of transmission between ant colonies remains unknown.

Objective

To investigate how the mycoparasite Escovopsis transmits between attine ant colonies by studying midden (waste tip) phenology in colonies of Acromyrmex subterraneus subterraneus and conducting laboratory experiments to understand spore characteristics and transmission mechanisms.

Results

Escovopsis was found in every midden sample (n=111), with 5.4% showing visible sporulation and 94.6% having cryptic presence. Middens were consistently built below nest entrances. Laboratory experiments showed Escovopsis spores exhibit dormancy that is broken by the presence of their Leucoagaricus host. Spores were found to readily attach to ant legs through phoretic transmission experiments. SEM revealed distinctive wall ornamentation on mature spores suggesting both phoretic and survival functions.

Conclusion

The study provides the first evidence of a mechanism for horizontal transmission of Escovopsis between attine colonies. The mycoparasite regularly sporulates on external waste middens, with spores adapted for survival and phoretic transmission. Rain splash and water runoff likely disperse dormant spores which can attach to passing ants. The spores remain dormant until encountering their fungal host within new colonies. This transmission is facilitated by the waste management behavior of Acromyrmex ants.
  • Published in:Royal Society Open Science,
  • Study Type:Field Study and Laboratory Experiments,
  • Source: 10.1098/rsos.161013
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