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Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection.
BMC Ecol. 2011 May 09; 11:13.BE

Abstract

BACKGROUND

Parasites that manipulate host behavior can provide prominent examples of extended phenotypes: parasite genomes controlling host behavior. Here we focus on one of the most dramatic examples of behavioral manipulation, the death grip of ants infected by Ophiocordyceps fungi. We studied the interaction between O. unilateralis s.l. and its host ant Camponotus leonardi in a Thai rainforest, where infected ants descend from their canopy nests down to understory vegetation to bite into abaxial leaf veins before dying. Host mortality is concentrated in patches (graveyards) where ants die on sapling leaves ca. 25 cm above the soil surface where conditions for parasite development are optimal. Here we address whether the sequence of ant behaviors leading to the final death grip can also be interpreted as parasite adaptations and describe some of the morphological changes inside the heads of infected workers that mediate the expression of the death grip phenotype.

RESULTS

We found that infected ants behave as zombies and display predictable stereotypical behaviors of random rather than directional walking, and of repeated convulsions that make them fall down and thus precludes returning to the canopy. Transitions from erratic wandering to death grips on a leaf vein were abrupt and synchronized around solar noon. We show that the mandibles of ants penetrate deeply into vein tissue and that this is accompanied by extensive atrophy of the mandibular muscles. This lock-jaw means the ant will remain attached to the leaf after death. We further present histological data to show that a high density of single celled stages of the parasite within the head capsule of dying ants are likely to be responsible for this muscular atrophy.

CONCLUSIONS

Extended phenotypes in ants induced by fungal infections are a complex example of behavioral manipulation requiring coordinated changes of host behavior and morphology. Future work should address the genetic basis of such extended phenotypes.

Authors+Show Affiliations

Departments of Entomology and Biology, Penn State University, PA 16802, USA. dhughes@psu.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21554670

Citation

Hughes, David P., et al. "Behavioral Mechanisms and Morphological Symptoms of Zombie Ants Dying From Fungal Infection." BMC Ecology, vol. 11, 2011, p. 13.
Hughes DP, Andersen SB, Hywel-Jones NL, et al. Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection. BMC Ecol. 2011;11:13.
Hughes, D. P., Andersen, S. B., Hywel-Jones, N. L., Himaman, W., Billen, J., & Boomsma, J. J. (2011). Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection. BMC Ecology, 11, 13. https://doi.org/10.1186/1472-6785-11-13
Hughes DP, et al. Behavioral Mechanisms and Morphological Symptoms of Zombie Ants Dying From Fungal Infection. BMC Ecol. 2011 May 9;11:13. PubMed PMID: 21554670.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection. AU - Hughes,David P, AU - Andersen,Sandra B, AU - Hywel-Jones,Nigel L, AU - Himaman,Winanda, AU - Billen,Johan, AU - Boomsma,Jacobus J, Y1 - 2011/05/09/ PY - 2011/03/17/received PY - 2011/05/09/accepted PY - 2011/5/11/entrez PY - 2011/5/11/pubmed PY - 2011/10/1/medline SP - 13 EP - 13 JF - BMC ecology JO - BMC Ecol. VL - 11 N2 - BACKGROUND: Parasites that manipulate host behavior can provide prominent examples of extended phenotypes: parasite genomes controlling host behavior. Here we focus on one of the most dramatic examples of behavioral manipulation, the death grip of ants infected by Ophiocordyceps fungi. We studied the interaction between O. unilateralis s.l. and its host ant Camponotus leonardi in a Thai rainforest, where infected ants descend from their canopy nests down to understory vegetation to bite into abaxial leaf veins before dying. Host mortality is concentrated in patches (graveyards) where ants die on sapling leaves ca. 25 cm above the soil surface where conditions for parasite development are optimal. Here we address whether the sequence of ant behaviors leading to the final death grip can also be interpreted as parasite adaptations and describe some of the morphological changes inside the heads of infected workers that mediate the expression of the death grip phenotype. RESULTS: We found that infected ants behave as zombies and display predictable stereotypical behaviors of random rather than directional walking, and of repeated convulsions that make them fall down and thus precludes returning to the canopy. Transitions from erratic wandering to death grips on a leaf vein were abrupt and synchronized around solar noon. We show that the mandibles of ants penetrate deeply into vein tissue and that this is accompanied by extensive atrophy of the mandibular muscles. This lock-jaw means the ant will remain attached to the leaf after death. We further present histological data to show that a high density of single celled stages of the parasite within the head capsule of dying ants are likely to be responsible for this muscular atrophy. CONCLUSIONS: Extended phenotypes in ants induced by fungal infections are a complex example of behavioral manipulation requiring coordinated changes of host behavior and morphology. Future work should address the genetic basis of such extended phenotypes. SN - 1472-6785 UR - https://www.unboundmedicine.com/medline/citation/21554670/Behavioral_mechanisms_and_morphological_symptoms_of_zombie_ants_dying_from_fungal_infection_ L2 - https://bmcecol.biomedcentral.com/articles/10.1186/1472-6785-11-13 DB - PRIME DP - Unbound Medicine ER -