Cordyceps unilateralis
Encyclopedia
Ophiocordyceps unilateralis is a parasitoid
fungus
that infects ant
s such as Camponotus leonardi, and alters their behavior in order to ensure the widespread distribution of its spore
s. This is a prime example of such a parasite.
in the Ophiocordyceps
genus, O. unilateralis targets a specific host species; which is ideally the Camponotus leonardi ant, but has been known to parasitize other closely related species of ants with lesser degrees of host manipulation and reproductive success.
The fungus's spores enter the body of the insect likely through the cuticle by enzymatic activity, where they begin to consume the non-vital soft tissues. Yeast stages of the fungus spread in the ant's body and presumably produce compounds that affects the ant's brain and change its behaviour by unknown mechanisms, causing the insect to climb up the stem of a plant and use its mandibles to secure itself to the plant. Infected ants bite the leaf veins with abnormal force, leaving telltale dumbbell-shaped marks. A search through plant fossil databases revealed similar marks on a fossil leaf from the Messel pit
which is 48 million years old.
The fungus then kills the ant, and continues to grow as its mycelia invade more soft tissues and structurally fortify the ant's exoskeleton. More mycelia then sprout out of the ant, and securely anchor it to the plant substrate while secreting antimicrobials to ward off competition. When the fungus is ready to reproduce, its fruiting bodies grow from the ant's head and rupture, releasing the spores. This process takes 4 to 10 days.
The changes in the behavior of the infected ants are very specific, giving rise to the term zombie ants, and tuned for the benefit of the fungus. The ants generally clamp to a leaf's vein about 25 cm above the ground, on the northern side of the plant, in an environment with 94-95% humidity and temperatures between 20 and 30°C. According to David Hughes, "You can find whole graveyards with 20 or 30 ants in a square metre. Each time, they are on leaves that are a particular height off the ground and they have bitten into the main vein [of a leaf] before dying". When the dead ants are repositioned in various other situations, further vegetative growth and sporulation either fails to occur or results in undersized and abnormal reproductive structures.
Six bioactive naphthoquinone
derivatives isolated from O. unilateralis, namely
showed anti-malarial
activity in vitro
.
There has also been research into the use of red naphthoquinone pigments made by O. unilateralis as a dye for food, cosmetic and pharmaceutical manufacturing processes.
Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
that infects ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s such as Camponotus leonardi, and alters their behavior in order to ensure the widespread distribution of its spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s. This is a prime example of such a parasite.
Morphology
The species can be identified at the end of its lifecycle by its reproductive structure, consisting of a wiry yet pliant darkly pigmented stroma stalk extending from the back of the deceased ant's head. The stalk has perithecia just below its tip.Life cycle
Like other fungi pathogenic to insectsEntomopathogenic fungus
An entomopathogenic fungus is a fungus that can act as a parasite of insects and kills or seriously disables them.-Typical life cycle:These fungi usually attach to the external body surface of insects in the form of microscopic spores...
in the Ophiocordyceps
Ophiocordyceps
Ophiocordyceps is a genus of fungi within the Ophiocordycipitaceae family. The widespread genus, first described scientifically by British mycologist Tom Petch in 1931, contains about 140 species that grow on insects...
genus, O. unilateralis targets a specific host species; which is ideally the Camponotus leonardi ant, but has been known to parasitize other closely related species of ants with lesser degrees of host manipulation and reproductive success.
The fungus's spores enter the body of the insect likely through the cuticle by enzymatic activity, where they begin to consume the non-vital soft tissues. Yeast stages of the fungus spread in the ant's body and presumably produce compounds that affects the ant's brain and change its behaviour by unknown mechanisms, causing the insect to climb up the stem of a plant and use its mandibles to secure itself to the plant. Infected ants bite the leaf veins with abnormal force, leaving telltale dumbbell-shaped marks. A search through plant fossil databases revealed similar marks on a fossil leaf from the Messel pit
Messel pit
The Messel Pit is a disused quarry near the village of Messel, about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance...
which is 48 million years old.
The fungus then kills the ant, and continues to grow as its mycelia invade more soft tissues and structurally fortify the ant's exoskeleton. More mycelia then sprout out of the ant, and securely anchor it to the plant substrate while secreting antimicrobials to ward off competition. When the fungus is ready to reproduce, its fruiting bodies grow from the ant's head and rupture, releasing the spores. This process takes 4 to 10 days.
The changes in the behavior of the infected ants are very specific, giving rise to the term zombie ants, and tuned for the benefit of the fungus. The ants generally clamp to a leaf's vein about 25 cm above the ground, on the northern side of the plant, in an environment with 94-95% humidity and temperatures between 20 and 30°C. According to David Hughes, "You can find whole graveyards with 20 or 30 ants in a square metre. Each time, they are on leaves that are a particular height off the ground and they have bitten into the main vein [of a leaf] before dying". When the dead ants are repositioned in various other situations, further vegetative growth and sporulation either fails to occur or results in undersized and abnormal reproductive structures.
Geographic distribution
Panglobal habitation of tropical forests, including those in Africa, Brazil and Thailand.Host impact
O. unilateralis has been known to destroy entire ant colonies. In response, ants have evolved the ability to sense that a member of the colony is infected; healthy ants will carry the dying one far away from the colony in order to avoid fungal spore exposure.Medicinal potential
The Ophiocordyceps fungus contains various known and untapped bioactive metabolites, and is being investigated as a new source of natural drugs with immunomodulatory, antitumor, hypoglycemic and hypocholesterolemic functions.Six bioactive naphthoquinone
Naphthoquinone
Naphthoquinone is a class of natural phenols based on the C6-C4 skeleton.1,4-Naphthoquinone can be viewed as derivatives of naphthalene through the replacement of two hydrogen atoms by two ketone groups....
derivatives isolated from O. unilateralis, namely
- erythrostominone
- deoxyerythrostominone
- 4-O-methyl erythrostominone|4-O-methyl erythrostominone
- epierythrostominol
- deoxyerythrostominol, and
- 3,5,8-trihydroxy-6-methoxy-2-(5-oxohexa-1,3-dienyl)-1,4-naphthoquinone
showed anti-malarial
Antimalarial drug
Antimalarial medications, also known as antimalarials, are designed to prevent or cure malaria. Such drugs may be used for some or all of the following:* Treatment of malaria in individuals with suspected or confirmed infection...
activity in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
.
There has also been research into the use of red naphthoquinone pigments made by O. unilateralis as a dye for food, cosmetic and pharmaceutical manufacturing processes.