A parasitic fungus is turning ants in Thailand into “zombies,” and now scientists have a better idea how and when the infection does its gruesome work. The fungus, a species of Ophiocordyceps, targets carpenter ants living high in Thailand's rain forest canopy.
In a 2009 paper, for instance, Hughes and colleagues reported on the surprising specificity of the fungus's “directions” to its zombie hosts. While normal ants rarely deviate from a trail along a tree, zombie ants wander aimlessly, and they suffer convulsions that cause the animals to fall out of the forest canopy.
Many species of carpenter ant, for instance, can cause structural damage to buildings as the bugs carve their nests in damp wood. Zombie Ant Bites, Facts, Habitat, Lifespan, Treatment, How to get rid of zombie ants and what do they eat etc questions are answered on this page.
Combatants are discovered by the British naturalist Alfred Russel Wallace in 1859. This ant species is susceptible to the fungal infection itself that related to the order Hypocrites.
Combatants are actually the victim of the entomopathogen which can act as a parasite insect to kill or seriously disable the host. Infected hosts leave their canopy nests and foraging trails in the forest to the area with a temperature and humidity which suitable for the fungal growth.
The process leading to mortality takes around 4-10 days which includes a reproductive stage. In the reproduction stage, fruiting bodies grow from the ant’s head rupturing to release the fungus’s spores.
Scientific NameOphiocordyceps UnilateralisSizeUp to 2 mm Max Envenom Type The Ants become the Combatants when the fungus attacking them which known as the Ophiocordyceps unilateralism. The fungus will force the ants to climb up on the leaf to reproduce.
The result, the jaw locked, and unable to release the leaf, even after death. The Camponotus Leonard ants live in tropical rainforest trees infected by the Ophiocordyceps unilateralism fungus.
Once it gets infected, the fungus will force it to climb up from its natural habitat and bite down on a leaf and then die. The infected and will stop doing regular tasks and after some time later leave the nest and search the place where the fungus can reproduce.
Their last bite on the leaf after which they lost the control on the open and closing muscles of jaw even afterward death. The zombie ant found in the tropical forests where you humans don’t have reach.
From sea creatures that lure their prey via a glowing “fishing rod,” carnivorous plants, and a fungus that literally turns ants into zombies. And it can be found not in science fiction, but in the forests of tropical countries like Brazil, where you can find ants with their jaws clamped shut around a plant’s central vein.
Chances are, these ants are already dead and their bodies have already fallen victims to a fungus called the Ophiocordyceps unilateralism, or codices for short. To further understand what the fungus does to its victims, the scientists doing the research decided to use a scanning electron microscope to take a peek at the muscle fibers in the jaws of infected ants.
“In infected muscles at the time of the death grip, … lines appear really swollen,” said Colleen Man gold, a molecular biologist at Penn State University. Besides literally turning ants into actual “zombies,” some types of codices are also used in modern medicine, including kidney disorders and male sexual problems.
Ophiocordyceps unilateralism is an insect-pathogenic fungus, discovered by the British naturalist Alfred Russel Wallace in 1859, and currently found predominantly in tropical forest ecosystems. Infected hosts leave their canopy nests and foraging trails for the forest floor, an area with a temperature and humidity suitable for fungal growth; they then use their mandibles to attach themselves to a major vein on the underside of a leaf, where the host remains after its eventual death.
The process leading to mortality takes 4–10 days, and includes a reproductive stage where fruiting bodies grow from the ant's head, rupturing to release the fungus's spores. Ophiocordyceps unilateralism and related species are known to engage in an active secondary metabolism, among other reasons, for the production of substances active as antibacterial agents that protect the fungus-host ecosystem against further pathogenesis during fungal reproduction.
Because of this secondary metabolism, an interest in the species has been taken by natural products chemists, with corresponding discovery of small molecule agents (e.g. of the polypeptide family) of potential interest for use as human immunomodulatory, anti-infective, and anticancer agents. After years of research, the taxonomy of Ophiocordyceps unilateralism is becoming increasingly clear.
There have been many debates about whether the zombie -ant fungus (and other fungi) belonged to one or to the other as Ophiocordyceps was only recently brought forward. The genus Codices comprises over 400 species, historically classified in the familyClavicipitaceae within the orderHypocreales.
The classification was based on different morphological characteristics such as coliform autosports and cylindrical ASCII. However, in 2007, important new molecular data was tested, and enabled them to reorganize the family Clavicipitaceae.
The new molecular phylogenetic studies contradicted the older classification and moved all Codices species forming a sister group with Tolypocladium, into Ophiocordycipitaceae. Following this study, multiple traits such as the production of darkly pigmented, hard to flexible stomata were defined as characteristics of the family Ophiocordycipitaceae.
There is a possibility that this resulted in or reinforced the reproductive isolation of the fungi, leading to its speciation. Following this, a study conducted in Brazil delimited using morphological comparison of the autosports, germination process and asexual morphs, four different Ophiocordyceps species.
More recently in 2018, 15 new O. unilateralism species were described based on classic taxonomic criteria, and macro-morphological data with a deeper focus on autosport and asexual morphology. Morphological traits were used and included both macro-morphological characters (e.g. typical single stoma arising from the host's dorsal pronoun, the as coma (perihelia) growing from the storm) and microscopic traits (e.g. the morphology of the autosports in terms of size, shape, station and germination).
Moreover, other traits such as the host and the location of the death grip were added to the analyses. The morphological study led to 15 new identified species, with 14 which were distributed in the core clade, and one in the subclade.
O. Albacongiuae O. blakebarnesii O. camponoti-atricipis O. camponoti-balzani O. camponoti-bispinosi O. camponoti-chartificis O. camponoti-femorati O. camponoti-floridani O. camponoti-hippocrepidis O. camponoti-indiani O. camponoti-leonardi O. camponoti- melanotic O. camponoti-nidulantis O. camponoti-novogranadensis O. camponoti-renggeri O. camponoti-saundersi O. halabalaensis O. kimflemingiae O. naomipierceae O. obtain O. polyrhachis-furcata O. culminate O. RAM O. satoi. Schematic representation of Ophiocordyceps unilateralism growing out of an infected host ant The zombie -ant fungus is easily identifiable when its reproductive structure becomes apparent on its dead host, usually a carpenter ant.
At the end of its life cycle, O. unilateralism typically generates a single, wiry yet pliant, darkly pigmented stoma which arises from the dorsal pronoun region of the ant once it is dead. Species complex have both a sexual (mesomorph) and an asexual morph (anymore).
O. Unilateralis species exhibit morphological variations which are most certainly due to their wide geographic range, from Japan to the Americas. Different subspecies of ant can occur within the same area, which means that in order to coexist they have to occupy different ecological niches.
Consequently, the fungi may have evolved at the subspecies level in order to maximize its fitness. It exhibits a single stoma with a Hirsute asexual morph, which arises from the dorsal neck region of the dead ant and produces a dark brown perihelia attached to its stalk.
Once the host is killed by the fungus, it is commonly found fixed through their mandibles onto the surfaces of leaves. Its species produce a stoma that grows laterally from the host's thorax which itself generates an orange as coma.
The subclade does not present the same extended phenotype with the famous “death grip” that O. unilateralism species typically exhibit. Their hosts usually die at the base of large trees in the Amazonian rainforest, among the moss carpets.
In tropical forests, the ant species Camponotus Leonard lives in the high canopy and has an extensive network of aerial trails. Sometimes the canopy gaps are too difficult to cross, so the ants trails descend to the forest floor where they are exposed to O. unilateralism spores.
The spores attach to their exoskeletons and eventually break through using mechanical pressure and enzymes. Like other fungi pathogenic to insects in the genus Ophiocordyceps, the fungus targets a specific host species, Camponotus Leonard ; despite this, the fungus may parasitize other closely related species of ants with lesser degrees of host manipulation and reproductive success.
An infected ant exhibits irregularly timed full-body convulsions that dislodge it from its canopy nest to the forest floor. The changes in the behavior of the infected ants are very specific, giving rise to the popular term zombie ants “.
Behaviors are tuned for the benefit of the fungus in terms of its growth and its transmission, thereby increasing its fitness. The ant climbs up the stem of a plant and uses its mandibles with abnormal force to secure itself to a leaf vein, leaving dumbbell-shaped marks on it.
When the dead ants are moved to other places and positions, further vegetative growth and population either fails to occur or results in undersized and abnormal reproductive structures. In temperate forests, the stereotypical behavior of zombie ants is to attach themselves to the lower side of twigs, not leaves.
A search of plant-fossil databases revealed similar marks on a fossil leaf from the Vessel Pit, which is 48 million years old. Once the mandibles of the ant are secured to the leaf vein, atrophy quickly sets in, destroying the sarcomere connections in the muscle fibers and reducing the mitochondria and sarcoplasmic reticular.
The ant is no longer able to control the muscles of the mandible and remains fixed in place, hanging upside-down on the leaf. This lockjaw trait is popularly known as the death grip and is essential in the fungus's lifecycle.
A study led in Thailand revealed that there is a synchronization of this manipulated biting behavior at solar noon. More mycelia than sprout out of the ant, securely anchoring it to the plant substrate while secreting antimicrobial 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. Schematic representation of the ant behavioral manipulation caused by natural products secreted by O. unilateralism.
Unilateralis' life cycle includes and depends on the infection and the manipulation of a carpenter ant, principally C. Leonard. The behavioral manipulation of the ant, which gives rise to the name zombie -ant”, is an extended phenotype of the fungus.
It first affects the ant's behavior through convulsions that make it fall from its high canopy nest onto the forest floor. This is followed by the fungus controlling the climbing of the ant and the locking of its jaw (and subsequent death) onto a leaf around 25 centimeters above the ground, which is thought to be the optimal height for fungal spore growth and dispersion.
During the infection the parasite comes across an array of environments such as different host tissues or the immune response. Studies have shown that O. unilateralism reacts heterogeneously by secreting different metabolites according to the host tissue it encounters and whether they are live or dead.
The first step O. unilateralism has to overcome to have a successful infection, is to attach itself onto the ant's cuticle and then infiltrate it. For this purpose, the fungus' alpha pierces the exoskeleton using enzymes such as Chinese, lipase and protease, combined with mechanical pressure.
After the fungus enters the ant it propagates, and fungal cells are found beside the host's brain. Once the population is of sufficient size, the fungus secretes compounds and takes over the central nervous system (CNS), which enables it to manipulate the ant to reach the forest floor and climb up the vegetation.
Two candidate compounds, sphingosine and guanidinobutyric acid (GBA), were identified as responsible for the manipulation of the host brain. Some studies identified another compound, hypoxanthine, present at high extracellular concentration.
Hypoxanthine has deleterious effects on neural tissues of the cerebral cortex, which in the context of zombie ants may indicate a way for the fungus to alter the motor neurons of the ant, consequently affecting its behavior. The behavior consists in the ant biting the leaf so tightly that the ant is prevented from falling as it dies hanging upside down, consequently enabling the proper growth of the fungus' fruiting body.
This is possibly a result of the atrophy of the ant's mandibular muscles caused by the secretion of fungal compounds. In multiple studies, fungal cell populations were found within atrophied mandibular muscle tissues.
More in depth research is needed for the identification of other fungal compounds which act to atrophy the mandibular muscles, and for the understanding of their exact effects on the ant. This is likely due to the heterogeneous nature of the fungus which secretes different metabolites according to host species.
Many studies describe Ophiocordyceps unilateralism distribution as pan tropical since it occurs mainly in tropical forest ecosystems. Its distribution includes tropical rainforests located in Brazil, Australia and Thailand, and temperate forests found in South Carolina, Florida and Japan.
The density of dead ants within these graveyards can vary according to climatic conditions. This means that environmental conditions such as humidity and temperature can influence O.unilateralism effects on the host population.
It is thought that large precipitation events at the beginning and the end of the rainy season stimulates fungal development, which leads to more spores being released and ultimately more individuals being infected and killed. O. unilateralism fungi produce various known secondary metabolites, as well as several structurally characterized substances.
These natural products are reportedly being investigated as potential leads in discovery efforts toward immunomodulatory, antitumor, hypoglycemic, and hypercholesterolemia targets. Naphthoquinone derivatives are an example of secondary metabolite with important pharmaceutical potentials produced by O. unilateralism.
Moreover, the use of red naphthoquinone pigments produced by O. unilateralism has been studied as a dye for food, cosmetic, and pharmaceutical manufacturing processes. These pigments are stable against acid / alkaline conditions and light and are not cytotoxic, which makes them applicable for food coloring and as a dye for other materials.
These attributes also make it a prime candidate for antituberculosis testing in secondary TB patients, by improving symptoms and enhancing immunity when combined with chemotherapeutic drugs. These secondary metabolites have been used in antibiotics such as Pauline, cholesterol medication such as compaction, and antifungal treatments.
It has also been reported that polypeptides have other therapeutic effects such as antitumor, antioxidant and antiaging activities. O. Unilateralis suffers from an unidentified fungal hyperparasite, reported in the lay press as the “antizombie-fungus fungus”, that results in only 6–7% of sporadic being viable, limiting the damage O. unilateralism inflicts on ant colonies.
The graveyards of dead ants are numerous and spread throughout the surrounding area of the colony. This is caused by the weakening of the fungus by the hyperparasite, which may limit the viability of infectious spores.
Ants also groom each other to combat microscopic organisms that could potentially harm the colony. This host manipulation is termed the “extended phenotype” of the parasite and is a form of adaptation.
Host ant manipulation by O. unilateralism represents one of the best-known examples of extended phenotypes. The extended phenotype of O. unilateralism typically depicts the infected ant leaving its canopy nest and its normal foraging path to reach the forest floor and subsequently climb up 25 cm above ground level.
This height is considered to be optimal for fungal growth due to its humidity level and temperature. This is followed by a “death grip” of the infected ant once at what is considered to be the optimal conditions for postmortem fungal development.
This leads to the fungus continuing its growth and releasing fungal spores onto the forest floor. These spores will then be encountered by the ants which, when the aerial foraging route is not possible, have to occasionally descend to ground level.
Some studies proposed a theory in which O. unilateralism has another possible form of adaptation which ensures its repeated reproduction. Species as they can produce and release within the air, clear and thin-walled spores which are susceptible to environmental conditions such as UV radiation and dryness.
In fact, studies suggest that the short viability of the fungal spores lead to the need of somatic investment (growth/survival) by the parasite in order to sustain the growth of the fungus' fruiting body on its host, thereby enabling successive reproduction. To do so, O. unilateralism fortifies the ant cadaver to prevent its decay, which consequently ensures the growth of the fruiting body.
Therefore, the zombie -ant fungus adapts to the short viability of its spores by increasing their production using the dead ant. O.unilateralism' principal hosts evolved efficient behavioral forms of social immunity.
In fact, the ants clean the exoskeletons of one another in order to decrease the presence of spores which are attached to their cuticle. Plus, there are reports testifying that most worker ants remain inside the nest boundaries, consequently, only foragers are at risk of infection.
In areas where O. unilateralism is present, C. Leonard builds its nests high in the canopy, and has a broad network of areal trails. These trails occasionally move down to the ground level, where infection and graveyards occur, due to canopy gaps too difficult for the ants to cross.
When the trails descend to the forest floor, their length is only of three to five meters before going back up into the canopy. Additionally, more evidence participates in the favor of this defense method being adaptive as it is not observed in undisturbed forests where the zombie -ant fungus is not present.
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