Life cycle and
characteristics of
Ophiocordyceps
Unilateralis
CRAIG WILT
Ophiocordyceps Unilateralis
• Found in tropical forests.
• Originally discovered in 1865
and was named Torrubia
Unilateralis by the Tulsane
brothers. (Tulsane 1865).
• It is commonly known as the
“zombie fungus”.
• Alters ants behavior for the
reproductive benefit of the
fungus through a series of
complex chemical reactions.
ophiocordyceptae
• Described by British Mycologist
Tom Petch in 1931.
• 140 known species and they are
characterized by their growth on
insects (Kirk 2008).
• Result of millions of years of
coevolution between the two
species.
Camponotus leonardi
• O. unilateralis specificity targets
Camponotus leonardi.
• Found throughout the world on
many continents.
• Build their homes in dead
hollowed out tress rather than
dirt.
• Black or brown in color.
• Size ranges from 0.64 to 2.5 cm.
(Hahn 2008).
Environment
• O. Unilateralis has been found in the tropical forests of Brazil and
Thailand.
• Require an environment which includes the presence of Carpenter
ants.
• Prefer high humidity and warm temperatures.
• One study found that the fungus operates in a seasonal pattern.
Peaks for infections were found in both rainy and dry seasons. The
data suggests the heavy rainfall at the beginning and end of the rainy
season promotes fungal growth. (Kobmoo 2013).
Infection
• Spore release: Fungus releases spores that scatter across the ground.
• Contact: As ants walk along the forest floor spores attach to their
cuticles.
• Invasion: Through enzymes and mechanical pressure spores force
themselves into ants body.
• Behavior: Fungus invades ants CNS causing ant to wander in random
patterns and begin to convulse.
Infection (cont.)
• Fungus encourages ant to climb nearby plants and attach to leaves.
• Mycelia growth throughout the ant’s body as well as the tarsus
portion of the legs which aids in attachment to the underside of
leaves.
• Around solar noon the fungus forces the ants to bite into the main
vein of a leaf. Followed by separating muscles in the ant’s mandible
causing its jaw to become locked and unable to separate from the
leaf.
• Rapid hypheal growth further anchoring the ant to the leaf. The
fruiting body erupts and spreads spores putting any nearby ants in
significant danger.
Stroma and perithecial pad
Infection (cont.)
• As the fungus grows in the dead ants it has been found to form an
orange tube like structure rich in carbon that extends throughout the
ants body. It is thought this structure may play a role in energy
storage (Anderson 2009).
• The hyphae and fungus of the stroma exhibit a brown and red or
purple color respectively due to pigments made from
naphthoquinones. This substance exhibits anti-microbial properties
and is thought to provide protection against competing bacteria.
(Anderson 2012).
Infection (cont.)
Longitudinal dissections of infected ant.
SEM of dead infected ant
Preferred conditions for reproduction
• As the fungus grows within the ant it
encourages it to move to a location
best suited for the fungus’
reproduction.
• Directs the ants up a plant to a north
facing leaf at a height of about 25 cm
above the ground.
• Prefer temperature of 20 to 30
degrees Celsius with 94 to 95 percent
humidity. (Attenborough 2006).
• Grip the primary vein of the northwest side of the plant. (Anderson
2009).
Reproduction
• Dead ant stage which describes infected ants often found on the
underside of leaves.
• Stroma stage characterized by the rod like structure that emerges
from the ants back.
• Perithecial pad stage which involves the formation of the spore
dispersion structure.
• Their observations found that O. Unilateralis can undergo the DA-S-P
cycle as many as five times and found the fungus could consecutively
produce the stroma three times and the perithecial pads twice.
(Kobmoo 2013).
Life Cycle
Reproduction (cont.)
• When ready to reproduce the sac-like
structures known as asci build up pressure
and launch ascospores (Anderson 2009).
• spores are spread throughout the forest floor
to be picked up by another ant.
• The fungus’ spores are typically released at
night. When dispersed cover an area of 1
meter-squared below the host.
• Spores are not well protected. infection must
occur shortly after reproduction before
spores degrade.
• Fungus is limited to infection only members
of C. Leonardi. Spores must be release often
and for long durations of time to compensate
(Anderson 2012).
Life Cycle
Summary
• Ophiocordyceps Unilateralis undergoes a complex parasitic lifecycles
based around infecting and altering the behavior of Camponotus
leonardi for its own reproductive advantage.
Citations
• Andersen S, Ferrari M, Evans H, Elliot S, Boomsma J, Hughes D. Disease Dynamics in a Specialized Parasite of Ant Societies.
Plos ONE [serial online]. May 2012;7(5):1-8. Available from: Academic Search Complete, Ipswich, MA. Accessed October
20, 2013.
• Tulasne LR, Tulasne C (1865) Selecta Fungorum Carpologia III. Paris Museum. 1-221:
• Kirk PM, Cannon PF, Minter DW, Stalpers JA. (2008). Dictionary of the Fungi (10th ed.). Wallingford, UK: CABI. p. 483.
ISBN 978-0-85199-826-8.
• KOBMOO N, MONGKOLSAMRIT S, TASANATHAI K, THANAKITPIPATTANA D, LUANGSA-ARD J. Molecular phylogenies reveal
host-specific divergence of Ophiocordyceps unilateralis sensu lato following its host ants. Molecular Ecology [serial online].
June 15, 2012;21(12):3022-3031. Available from: Academic Search Complete, Ipswich, MA. Accessed October 20, 2013.
• Attenborough, David. "Cordyceps: attack of the killer fungi - Planet Earth Attenborough BBC wildlife". BBC Worldwide.
Retrieved 4/21/13.
• Andersen S, Gerritsma S, Hughes D, et al. Natural History Note: The Life of a Dead Ant: The Expression of an Adaptive
Extended Phenotype. American Naturalist [serial online]. September 2009;174(3):424-433. Available from: Academic
Search Complete, Ipswich, MA. Accessed October 20, 2013.