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Three-dimensional visualization and a deep-learning model reveal complex fungal parasite networks in behaviorally manipulated ants

Summary

This research reveals how a parasitic fungus takes control of carpenter ants by creating complex networks throughout the ant’s body, but surprisingly not in the brain. Using advanced microscopy and artificial intelligence, scientists discovered that the fungus forms interconnected cellular networks that surround the ant’s muscles, potentially allowing the fungus to coordinate its attack and share resources. This finding changes our understanding of how parasites can control host behavior. Impacts on everyday life: • Provides new insights into how parasites can control host behavior, which could help develop treatments for parasitic infections • Demonstrates novel applications of artificial intelligence in biological research • Advances our understanding of how organisms can work collectively to achieve complex tasks • Could lead to new strategies for pest control in agriculture • Helps explain natural phenomena that people might observe in their environment, such as infected ants attached to vegetation

Background

Some parasitic microbes have evolved the ability to adaptively manipulate the behavior of animals they infect. Examples include Trypanosomes altering salivary composition in tsetse flies, fungi inducing ants to bite vegetation, and Toxoplasma gondii causing rodents to lose fear of cats. Understanding how these small microbes control larger animal hosts to produce such extended phenotypes is an important question.

Objective

To examine the cell-level interactions between the fungal parasite Ophiocordyceps unilateralis sensu lato and its carpenter ant host Camponotus castaneus at the crucial moment when the manipulated host permanently attaches itself to a substrate by its mandibles. The study aimed to visualize and analyze the distribution, abundance and interactions of the fungus inside the manipulated host’s body.

Results

The fungus O. unilateralis s.l. was found throughout the host body but notably absent from the brain. Fungal cells formed extensive networks via conidial anastomosis tubes (CATs) connecting individual cells, with 59% of hyphal bodies connected to at least one other cell. The fungus invaded muscle fibers and created 3D networks encircling the muscles. The specialist parasite showed different growth patterns compared to the generalist B. bassiana, which did not form such networks.

Conclusion

The study reveals that behavioral manipulation by O. unilateralis s.l. does not require direct brain invasion, but rather occurs through peripheral effects. The formation of connected fungal networks throughout the host body suggests collective behavior may be an important strategy for this parasite. These networks may aid in nutrient transport and coordination of host manipulation.
  • Published in:Proceedings of the National Academy of Sciences of the United States of America,
  • Study Type:Laboratory Research Study,
  • Source: 10.1073/pnas.1711673114
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