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Ophiocordyceps unilateralis, známý také jako zombie houba, je druh parazitické houby, která napadá mravence rodu Camponotus. Tento vztah je jedním z příkladů manipulace parazita svým hostitelem. K parazitismu dochází nejčastěji v tropických deštných lesích.
Mravenec s nedostatkem živin je nucen slézt dolů ze stromu, kde se nacházejí spory houby. Spory napadnou mravence přes kutilkulu, dostávají se do nervové soustavy a začínají produkovat chemickou látku, která ovládá mravence. Bohužel zatím není známo, o jakou směs látek se jedná. Vědci mnoho látek při výzkumu ani neznali, je ale zajímavé, že se látky lišily, podle toho jaká houba napadala jakého mravence.
Tato infekce trvá 6 dní, poté je mravenec přinucen opustit své hnízdo. Zakousne se na spodní stranu listu do hlavní cévy listové žilnatiny, přibližně 25 cm nad zemí, v místě s velmi vysokou vlhkostí a teplotou mezi 20 a 30 °C. Toto jsou nejideálnější podmínky pro houbu k rozmnožování.
Zatímco mravenec umírá, houba nadále šíří hyfy, přemění vnitřní orgány na cukr, aby mohla lépe růst. Svalovou soustavu nechává bez povšimnutí, aby měla jistotu, že mravenec zůstane stále přichycený na spodní straně listu. Ani vnějšího obalu si nevšímá, až na jedno místo, v zadní části hlavy mravence vyroste stopka. Nechce totiž, aby houbu napadly mikroby nebo jiné houby.
Po 2 týdnech stopka dosáhne dvojnásobné velikosti mravence, vyroste plodnice a výtrusy spadnou na zem, kde vytvoří „infekční pole“, do kterého když mravenec vstoupí, je téměř jistotou, že se nakazí.
S touto parazitickou houbou se nejčastěji setkáváme na území deštných pralesů Thajska, Brazílie a jejich okolí.
Mravenci si vyvinuli jistou formu ochrany před nákazou, staví si hnízda ve stromech. Nedostatek živin je však zažene dolů, kde se mohou nakazit touto parazitickou houbou. Další adaptací může být to, že se vyhýbají místům, kde se vyskytují ostatní mrtví mravenci stejného druhu.
Houby O. unilateralis a její příbuzné druhy mají schopnost aktivního sekundárního metabolismu, když produkují protilátky na ochranu mravence před napadení mikroby při rozmnožování houby uvnitř těla mravence. Jejich agens (konkrétně Polyketid) zaujal vědce jako potenciální Imunomodulátor.
Obrázky, zvuky či videa k tématu Ophiocordyceps unilateralis ve Wikimedia Commons
Ophiocordyceps unilateralis, známý také jako zombie houba, je druh parazitické houby, která napadá mravence rodu Camponotus. Tento vztah je jedním z příkladů manipulace parazita svým hostitelem. K parazitismu dochází nejčastěji v tropických deštných lesích.
Ophiocordyceps unilateralis ist eine parasitische Pilz-Art, die auf Ameisen wächst und deren Verhalten so manipuliert, dass der Wirt keine Kontrolle über seinen eigenen Körper hat.
Durch die pantropische Verbreitung und das Vorkommen auf verschiedenen Wirtsarten ist der Pilz sehr variabel und es sind mehrere Anamorphe beschrieben.[1] Die Fruchtkörper bestehen aus einer drahtigen aber biegsamen dunkel pigmentierten Keule, die direkt aus der Rückseite des Kopfes der verendeten Ameise wächst. Seitlich befindet sich die Fruchtschicht in Form von Platten, das Stroma, in dem Perithecien gebildet werden, aus denen die relativ großen Sporen freigegeben werden.[2] Bei manchen Formen erscheinen die Platten mit den Perithecien endständig, bei anderen verfließen sie ineinander und es bildet sich ein Köpfchen.[1]
Die Pilzsporen keimen auf dem Exoskelett von Ameisen. Befallen werden vor allem Camponotus leonardi, aber auch andere Vertreter der Rossameisen und Arten von Polyrhachis.[2] Allerdings handelt es sich wahrscheinlich um mehrere Arten (siehe Systematik). Die Hyphen dringen in den Körper des Insekts ein, wandern ins Gehirn und beeinflussen dessen Verhalten. Das Insekt bewegt sich nach einer Infektionsperiode von drei bis sechs Tagen an einen Platz, der für den Pilz optimale Lebensbedingungen bietet und stirbt dort. Der Pilz manipuliert die Ameise so, dass sie sich auf Oberflächen wie Blattunterseiten oder Rinden festbeißt. Dieses Verhalten wird als erweiterter Phänotyp des Pilzes gedeutet, da das Festbeißen eine Ortsfixierung für den Pilz bedeutet und optimierte Umweltbedingungen für die Fruchtkörperentwicklung schafft.[2] Oft werden hohe Dichten an toten Ameisen in tropischen Wäldern beobachtet, sodass diese Funde als Friedhöfe bezeichnet werden. Der Pilz bildet nun die Fruchtkörper und neue Sporen.[3] Die für eine Windverbreitung zu schweren Sporen fallen zu Boden, bilden dort Sekundärsporen, infizieren vorbeilaufende Ameisen und schließen so den Zyklus.[4] Die Ameisen bauen als mutmaßliche Ausweichstrategie ihre Nester meist weit oben in den Baumkronen und kommen nur selten auf den Boden, wo die Infektionsgefahr am größten ist, da der Pilz hohe Luftfeuchte benötigt. Der Pilz kommt weltweit in tropischen und subtropischen Wäldern vor.[1] In der Grube Messel wurden 48 Millionen Jahre alte Fossilfunde von Ameisen gefunden, die sich in Blätter verbissen haben, was das Alter dieser Verhaltensmanipulation unterstreicht.[5]
Ophiocordyceps unilateralis wurde lange wie alle Kernkeulen in die Gattung Cordyceps innerhalb der Clavicipitaceae gestellt. Inzwischen werden die Kernkeulen aber in drei Gattungen in zwei verschiedenen Familien aufgeteilt. Ophiocordyceps unilateralis wird zu den Ophiocordycipitaceae gestellt[6]. Jüngste Untersuchungen zeigen, dass Ophiocordyceps unilateralis ein ganzer Artenkomplex ist. Schon in einem relativ engen Gebiet in Minas Gerais in Brasilien wurden vier vorher zu Ophiocordyceps unilateralis gestellte neue Arten entdeckt, die auf jeweils eine Ameisenart spezialisiert sind.[7]
Ophiocordyceps unilateralis enthält einige bioaktive Substanzen, die potenzielle Mittel zur Immunmodulation, gegen Tumoren, Hyperglykämie und Hypercholesterinämie darstellen.[8] Sechs bioaktive Naphthochinon-Derivate wurden aus Ophiocordyceps unilateralis isoliert, die in vitro Wirkung gegen Malaria zeigten.[9][10] Es gibt auch Untersuchungen, die rote Naphthochinonpigmente als Farbstoff in der Lebensmittel- oder Kosmetikindustrie zu nutzen.[11]
In der PlayStation-3/PlayStation-4-Spielreihe The Last of Us infiziert ein Pilz die Gehirne von Menschen und verwandelt sie so in äußerst aggressive, zombieähnliche Lebewesen, die andere Menschen attackieren, um den Pilz zu verbreiten. Die Produzenten gaben an, von Ophiocordyceps unilateralis inspiriert worden zu sein.[12]
Der Autor M. R. Carey veröffentlichte 2014 seinen postapokalyptischen Roman The Girl with All the Gifts, in dem ebenfalls zombieähnliche Mutanten (“Hungries”) von einer Variante von Ophiocordyceps unilateralis befallen sind.[13]
In der sechsten Episode der Fernsehserie Legion wird der Pilz mit Liebe verglichen.[14]
Im russischen Horrorfilm Superdeep (2020) werden Menschen von pilzartigen Parasiten befallen und verlieren daraufhin die Kontrolle über ihren Körper. Ein Wissenschaftler stellt eine Verbindung zu Ophiocordyceps unilateralis her und erklärt dessen Wirkung auf Ameisen.
Ophiocordyceps unilateralis ist eine parasitische Pilz-Art, die auf Ameisen wächst und deren Verhalten so manipuliert, dass der Wirt keine Kontrolle über seinen eigenen Körper hat.
Ophiocordyceps unilateralis, commonly known as zombie-ant fungus,[2] is an insect-pathogenic fungus, discovered by the British naturalist Alfred Russel Wallace in 1859, and currently found predominantly in tropical forest ecosystems. O. unilateralis infects ants of the tribe Camponotini, with the full pathogenesis being characterized by alteration of the behavioral patterns of the infected ant. 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.[3] The process, leading up 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. O. unilateralis is, in turn, also susceptible to fungal infection itself, an occurrence that can limit its impact on ant populations, which has otherwise been known to devastate ant colonies.
Ophiocordyceps unilateralis 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 polyketide family) of potential interest for use as human immunomodulatory, anti-infective, and anticancer agents.
After years of research, the taxonomy of Ophiocordyceps unilateralis is becoming increasingly clear.
Throughout history there has been confusion about the distinction between the genera Cordyceps and Ophiocordyceps. 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 Cordyceps comprises over 400 species, historically classified in the family Clavicipitaceae within the order Hypocreales. The classification was based on different morphological characteristics such as filiform ascospores and cylindrical asci.[4] When Cordyceps were first classified, there was no concrete evidence for the genus Ophiocordyceps. However, in 2007, important new molecular data was tested, and enabled them to reorganize the family Clavicipitaceae. It was found that Clavicipitaceae was in fact three distinct monophyletic families: the Clavicipitaceae, the Cordycipitaceae and the Ophiocordycipitaceae.[4]
The new molecular phylogenetics studies contradicted the older classification and moved all Cordyceps species forming a sister group with Tolypocladium, into Ophiocordycipitaceae. Fungi able to parasitize ants were also included in the transfer, such as Cordyceps unilateralis which was later renamed Ophiocordyceps unilateralis.[5] Following this study, multiple traits such as the production of darkly pigmented, hard to flexible stromata were defined as characteristics of the family Ophiocordycipitaceae.[5]
The fungus's scientific name is sometimes written as Ophiocordyceps unilateralis sensu lato, which means 'in the broad sense', because the species actually represents a complex of many species within O. unilateralis.[6]
Support for this term has become increasingly important. In 2011, it was hypothesized that the zombie-ant fungus could actually be described as a complex of species which are host-specific, meaning that one O. unilateralis species can only successfully infect and manipulate one host ant species.[3] 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 comparisons of the ascospores, germination processes, and asexual morphs, four different Ophiocordyceps species. Afterwards, three new species were described in the Brazilian Amazon, six in Thailand, and one in Japan.[7]
More recently in 2018, 15 new O. unilateralis species were described based on classic taxonomic criteria, and macro-morphological data with a deeper focus on ascospore and asexual morphology. The asexual morphologies made it possible to distinguish two different clades mainly composed of species associated with ants which they termed "O. unilateralis core clade" and "O. kniphofioides subclade."[5]
Further analyses were conducted using a set of different traits. Morphological traits were used and included both macro-morphological characters (e.g. typical single stroma arising from the host's dorsal pronotum, the ascoma (perithecia) growing from the stroma) and microscopic traits (e.g. the morphology of the ascospores in terms of size, shape, septation and germination). Moreover, other traits such as the host and the location of the death grip were added to the analyses.[5] The morphological study led to 15 new identified species, with 14 which were distributed in the core clade, and one in the subclade. Moreover, it was found that species in the O. kniphofioides subclade specialise on neotropical ants, whereas species in the core clade specialise on Camponotini species.[5]
Species within the O. unilateralis core clade as described in 2018:[5]
Species within the O. kniphofioides subclade as described in 2018:[5]
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. unilateralis typically generates a single, wiry yet pliant, darkly pigmented stroma which arises from the dorsal pronotum region of the ant once it is dead.[8] Moreover, perithecia, the spore-bearing sexual structure, can be observed on the stalk, just below its tip.[4] This complex forms the fungus' fruiting body.
Most species within the O. unilateralis s.l. species complex have both a sexual (teleomorph) and an asexual morph (anamorph). These are different in terms of their function and characteristics. Generally, the asexual morphs identified for Ophiocordyceps are Hirsutella and Hymenostilbe, two genera of asexually reproducing fungi.[8]
O. unilateralis species exhibit morphological variations which are most certainly due to their wide geographic range, from Japan to the Americas. Moreover, it has been hypothesized that their morphological variations may also be a result of one fungus species maximizing its infection on one specific host ant species (host-specific infections). 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.[7]
The O. unilateralis core clade, as described in 2018, has distinct morphological characteristics. It exhibits a single stroma with a Hirsutella asexual morph, which arises from the dorsal neck region of the dead ant and produces a dark brown perithecia attached to its stalk.[5] These species are also recognizable through the host species they infect, which are only Camponotini species. Once the host is killed by the fungus, it is commonly found fixed through their mandibles onto the surfaces of leaves.[5]
The O. kniphofioides subclade, as described in 2018, also has distinct morphological characteristics. Its species produce a stroma that grows laterally from the host's thorax which itself generates an orange ascoma. Moreover, species within this subclade share a Hirsutella asexual morph.[5] As for the core clade, these species are also recognizable through the hosts they infect, which are usually neotropical ant species. The subclade does not present the same extended phenotype with the famous "death grip" that O. unilateralis species typically exhibit. Their hosts usually die at the base of large trees in the Amazonian rainforest, among the moss carpets.[5]
In tropical forests, the ant species Camponotus leonardi 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. unilateralis spores. The spores attach to their exoskeletons and eventually break through using mechanical pressure and enzymes.[8] Like other fungi pathogenic to insects in the genus Ophiocordyceps, the fungus targets a specific host species, Camponotus leonardi; despite this, the fungus may parasitize other closely related species of ants with lesser degrees of host manipulation and reproductive success.[9]
Yeast stages of the fungus spread in the ant's body and presumably produce compounds that affect the ant's hemocoel, using the evolutionary trait of an extended phenotype to manipulate the behavioral patterns exhibited by the ant.[10] An infected ant exhibits irregularly timed full-body convulsions that dislodge it from its canopy nest to the forest floor.[11]
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. The ants generally clamp to a leaf's vein at a height of 26 cm above the forest floor,[10] on the northern side of the plant, in an environment with 94–95% humidity and temperatures between 20 and 30 °C (68 and 86 °F). Infections may lead to 20 to 30 dead ants per square meter.[12] When the dead ants are moved to other places and positions, further vegetative growth and sporulation either fails to occur or results in undersized and abnormal reproductive structures.[10] In temperate forests, the typical behavior of zombie ants is to attach themselves to the lower side of twigs, not leaves.[13]
A search of plant-fossil databases revealed similar marks on a fossil leaf from the Messel Pit, which is 48 million years old.[14][15] 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.[11] A study led in Thailand revealed that there is a synchronization of this manipulated biting behavior at solar noon.[13]
The fungus then kills the ant and continues to grow as its hyphae invade more soft tissues and structurally fortify the ant's exoskeleton.[9] More mycelia then sprout out of the ant, securely anchoring it to the plant substrate while secreting antimicrobials to ward off competition.[9] When the fungus is ready to reproduce, its fruiting bodies grow from the ant's head and rupture, releasing the spores. This process takes 4–10 days.[9] Dead ants are found in areas termed "graveyards" which contain high densities of dead ants previously infected by the same fungus.[16]
The term "zombie ants" has been used in popular media as well as scientific articles, but has also been described as "catchy, yet misleading."[17][18]
O. unilateralis' life cycle includes and depends on the infection and the manipulation of a carpenter ant, principally C. leonardi.[3] 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.[11] 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 centimetres above the ground, which is thought to be the optimal height for fungal spore growth and dispersion.[11]
Throughout the lifecycle, unique challenges must be met by equally unique metabolic activities. The fungal pathogen must attach securely to the arthropod exoskeleton and penetrate it—avoiding or suppressing host defenses—then, control the behavior of the host before killing it; and finally, it must protect the carcass from microbial and scavenger attack.[8]
The behavioral manipulation of the ant would not be possible without the presence of huge fungal cell populations beside the host's brain[13] and within muscles[19] because these lead to the secretion of various metabolites known to have important behavioral consequences.[20] During the infection the parasite comes across an array of environments such as different host tissues or the immune response.[20] Studies have shown that O. unilateralis reacts heterogeneously by secreting different metabolites according to the host tissue it encounters and whether they are live or dead.[19] The identification of these natural products is important in order to understand which aspects of the ants are under control and consequently how O. unilateralis manipulates the ant.
Two candidate compounds, sphingosine and guanidinobutyric acid (GBA), have been identified as responsible for the manipulation of the host brain. Both compounds are known to be involved in various neurological disorders. However, more research is needed to determine whether other fungal metabolites interact with the host brain to cause higher levels of sphingosine and GBA.[13]
Some studies identified another compound, hypoxanthine, present at high extracellular concentrations. 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.[19]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.
Effects of O. unilateralis on the host have been found to vary according to host species. The ant species which are normally found infected in nature exhibit a manipulated behavior, whereas the species which are not typically infected are killed by the infection, but their behavior is not altered. This is likely due to the heterogeneous nature of the fungus which secretes different metabolites according to host species.[13]
Many studies describe Ophiocordyceps unilateralis distribution as pantropical since it occurs mainly in tropical forest ecosystems.[6] However, there are some reports of the zombie-ant fungus in warm-temperate ecosystems.[13]
Its distribution includes tropical rainforests located in Brazil, Australia and Thailand, and temperate forests found in South Carolina, Florida and Japan.[5]
A 48-million-year-old fossil of a leaf stem exhibiting dumbbell-shaped marks characteristic of those made by an ant in the death-grip of Ophiocordyceps unilateralis was discovered in the Messel pit (Germany).[22]
When O. unilateralis-infected ants die, they are mainly located in regions containing a high density of ants which were previously manipulated and killed.[16] These areas are termed "graveyards" and can be of 20 to 30 meters in range[23] (with a local density of dead ants possibly exceeding 25 meters square).[11]
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.unilateralis' effects on the host population.[23] In fact, studies have described seasonal patterns in the density of previously infected dead ants, with an increase during the rainy season and a decrease during the dry season.[3] It is thought that large precipitation events at the beginning and the end of the rainy season stimulates fungal development,[3] which leads to more spores being released and ultimately more individuals being infected and killed.
Ophiocordyceps are known in the pharmaceutical world to be a medically-important group.[7] O. unilateralis fungi produce various known secondary metabolites, as well as several structurally uncharacterised substances. These natural products are reportedly being investigated as potential leads in discovery efforts toward immunomodulatory, antitumor, hypoglycemic, and hypocholesterolemic targets.[24]
In an Ophiocordyceps species within Japanese cicadas, the Ophiocordyceps replaces the symbiotic bacteria within the cicadas to help the host process sap as nutrients, unlike other related species, such as the Ophiocordyceps sinensis, which is a traditional immune booster and cancer treatment in Tibetan and Chinese culture.[25]
Naphthoquinone derivatives are an example of secondary metabolite with important pharmaceutical potentials produced by O. unilateralis. Six known naphthoquinone derivatives have been isolated from O. unilateralis, namely erythrostominone, deoxyerythrostominone, 4-O-methyl erythrostominone, epierythrostominol, deoxyerythrostominol, and 3,5,8-trihydroxy-6-methoxy-2-(5-oxohexa-1,3-dienyl)-1,4-naphthoquinone, which have shown activity in in vitro assays related to antimalarial drug discovery.[26][27] In addition to having antimalarial activities, all six of these secondary metabolites have been demonstrated to have anticancer and antibacterial activities.[28]
Moreover, the use of red naphthoquinone pigments produced by O. unilateralis has been studied as a dye for food, cosmetic, and pharmaceutical manufacturing processes.[29] In fact, naphthoquinone derivatives produced by the fungus show a red color under acidic conditions, and a purple color under basic conditions. 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.[30][31]
In 2009, a study showed that O. unilateralis also produces polyketides. These secondary metabolites have been used in antibiotics such as patulin, cholesterol medication such as compactin, and antifungal treatments. It has also been reported that polyketides have other therapeutic effects such as antitumor, antioxidant and antiaging activities.[32]
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 sporangia being viable, limiting the damage O. unilateralis inflicts on ant colonies. The hyperparasite moves in to attack O. unilateralis as the fungal stalk emerges from the ant's body, which can stop the stalk from releasing its spores.[33][34]
The graveyards of dead ants are numerous and spread throughout the surrounding area of the colony. Though O. unilateralis is very virulent, only about 6.5% of all fruiting bodies are viable spore producers. 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. Additional fungi also grant beneficial assistance to the colony.[34]
In host–parasite dynamics, both the host and the parasite are under selective pressure: the parasite evolves to increase its transmission, whereas the host evolves to avoid and/or resist the infection by the parasite.
Some parasites have evolved to manipulate their host's behavior in order to increase their transmission to uninfected susceptible individuals, thereby increasing their fitness.[23] This host manipulation is termed the "extended phenotype" of the parasite and is a form of adaptation. Host ant manipulation by O. unilateralis represents one of the best-known examples of extended phenotypes.[11]
The extended phenotype of O. unilateralis 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 it is to be found at what are considered to be optimal conditions for post-mortem fungal development. This leads to the fungus continuing its growth and releasing fungal spores onto the forest floor.[20] 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.[23] Therefore, O. unilateralis controls the ant's behavior and this manipulation represents an adaptation for the fungus where natural selection acts on its genes, increasing the fungus' fitness.[20]
Some studies proposed a theory in which O. unilateralis has another possible form of adaptation which ensures its repeated reproduction. This would be crucial for O. unilateralis s.l. 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.[34]
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. unilateralis 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.[34]
The principal hosts of O. unilateralis evolved adaptive behaviors able to limit the contact rate between uninfected susceptible hosts and infected hosts, thereby reducing the risk of transmission.
O.unilateralis' 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.[11] Also, ants can sense that a member of the colony is infected, resulting in healthy ants carrying the O. unilateralis-infected individual far away from the colony to avoid fungal spore exposure. Plus, there are reports testifying that most worker ants remain inside the nest boundaries; consequently, only foragers are at risk of infection.[34]
Moreover, one of the fungus' principal hosts, Camponotus leonardi, provided evidence for the avoidance of the forest floor by the host ants as a defence method.[23] In areas where O. unilateralis is present, C. leonardi builds its nests high in the canopy, and has a broad network of aerial 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. This demonstrates the avoidance of the zones of infection by the ants. Additionally, more evidence participates in the favour of this defence method being adaptive as it is not observed in undisturbed forests where the zombie-ant fungus is not present.[23]
In the video game series The Last of Us, Ophiocordyceps unilateralis has evolved to infect humans, thus creating zombie-like enemies in the game. Also, in episode two of the 2023 television series The Last of Us on HBO Max,[35] Ophiocordyceps unilateralis is revealed to be the primary cause of the infected outbreak and subsequent collapse of human civilization. In the show, the fungus, having adapted to higher temperatures due to climate change, takes control of humans (as opposed to insects) as an alternative host and causes them to exhibit erratic behaviors, such as the desire to attack and infect non-infected humans. Craig Mazin, who co-wrote and produced the series, said that everything the series suggests fungi do, they have done forever in real life.[36]
Ophiocordyceps unilateralis, commonly known as zombie-ant fungus, is an insect-pathogenic fungus, discovered by the British naturalist Alfred Russel Wallace in 1859, and currently found predominantly in tropical forest ecosystems. O. unilateralis infects ants of the tribe Camponotini, with the full pathogenesis being characterized by alteration of the behavioral patterns of the infected ant. 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 up 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. O. unilateralis is, in turn, also susceptible to fungal infection itself, an occurrence that can limit its impact on ant populations, which has otherwise been known to devastate ant colonies.
Ophiocordyceps unilateralis 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 polyketide family) of potential interest for use as human immunomodulatory, anti-infective, and anticancer agents.
Ophiocordyceps unilateralis es una especie de hongo ascomiceto de la familia Clavicipitaceae. Comparte con el resto de sus congéneres el ser parasitoide. Ophiocordyceps unilateralis es capaz de modificar la conducta de las hormigas que infecta, específicamente de la tribu Camponotini, haciéndolas subir a la parte superior de una planta donde se anclan a la nervadura de una hoja con sus mandíbulas antes de morir, asegurando una distribución máxima de las esporas procedentes del cuerpo fructífero que brota del cadáver del insecto.
Como otros hongos patogénicos para los insectos en el género de los Ophiocordyceps, O. Unilateralis tiene preferencia por una especie de huésped determinado, en este caso la hormiga Camponotus leonardi, pero se sabe que puede parasitar otras especies similares de hormigas con menos éxito en el control del huésped y en la reproducción.
Las esporas del hongo entran en el cuerpo del insecto probablemente a través de la cutícula mediante actividad enzimática donde empiezan a consumir los tejidos no vitales. El hongo se expande por el cuerpo de la hormiga y probablemente produce compuestos que afectan al sistema nervioso de la misma, cambiando su comportamiento mediante mecanismos hasta ahora desconocidos, provocando que el insecto escale el tallo de una planta y use sus mandíbulas para fijarse a la misma.
El hongo entonces mata a la hormiga y continúa creciendo hasta que su micelio invade más tejidos blandos y refuerza estructuralmente el exoesqueleto de la hormiga. Más micelios salen de la hormiga y se anclan a la planta mientras secretan antimicrobiales para eliminar la competencia. Cuando el hongo está preparado para reproducirse, sus esporocarpos crecen de la cabeza de la hormiga y se abren liberando las esporas. Este proceso dura entre 4 y 10 días.
Ophiocordyceps unilateralis es una especie de hongo ascomiceto de la familia Clavicipitaceae. Comparte con el resto de sus congéneres el ser parasitoide. Ophiocordyceps unilateralis es capaz de modificar la conducta de las hormigas que infecta, específicamente de la tribu Camponotini, haciéndolas subir a la parte superior de una planta donde se anclan a la nervadura de una hoja con sus mandíbulas antes de morir, asegurando una distribución máxima de las esporas procedentes del cuerpo fructífero que brota del cadáver del insecto.
Ophiocordyceps unilateralis est un champignon entomopathogène parasitant les fourmis de la tribu des Camponotini, découvert en 1859 par le naturaliste Alfred Russel Wallace. Présent en milieu forestier tropical, notamment sur les feuilles en décomposition, ce champignon ascomycète de la famille des Ophiocordycepitaceae infecte la fourmi en altérant ses schèmes de comportement, la pathogenèse complète l'incitant à quitter son nid de canopée et ses milieux de prospections habituels pour préférer le sol forestier, dont l'humidité et la température sont plus propices à la croissance fongique. Au bout de 4 à 10 jours, l'hôte gagne les hauteurs pour s'attacher à la nervure principale d'une feuille, en s'y agrafant par ses mandibules, jusqu'à sa mort, après la reproduction quand les fructifications du champignon sortent de la tête de la fourmi en la faisant éclater. Un stipe pousse hors de la fourmi pour ensuite libérer les spores, qui iront contaminer d'autres victimes[2].
Ophiocordyceps unilateralis et les espèces apparentées sont connus pour s'engager dans un métabolisme secondaire actif, entre autres raisons, pour la production de substances actives en tant qu'agents antibactériens qui protègent l'écosystème hôte-champignon contre une nouvelle pathogenèse pendant la reproduction fongique. En raison de ce métabolisme secondaire, les chimistes des produits naturels s'intéressent à l'espèce, avec la découverte correspondante d'agents à petites molécules (par exemple de la famille des polycétides) présentant un intérêt potentiel pour une utilisation en tant qu'agents immunomodulateurs, anti-infectieux et anticancéreux humains.
Selon Index Fungorum (3 août 2017)[1], le nom d’espèce Ophiocordyceps unilateralis est le nom valide, mais selon Index Fungorum (3 août 2017)[1], c’est un synonyme et le nom valide est Cordyceps unilateralis (Tul.) Sacc., 1878.
Ophiocordyceps unilateralis est un champignon entomopathogène parasitant les fourmis de la tribu des Camponotini, découvert en 1859 par le naturaliste Alfred Russel Wallace. Présent en milieu forestier tropical, notamment sur les feuilles en décomposition, ce champignon ascomycète de la famille des Ophiocordycepitaceae infecte la fourmi en altérant ses schèmes de comportement, la pathogenèse complète l'incitant à quitter son nid de canopée et ses milieux de prospections habituels pour préférer le sol forestier, dont l'humidité et la température sont plus propices à la croissance fongique. Au bout de 4 à 10 jours, l'hôte gagne les hauteurs pour s'attacher à la nervure principale d'une feuille, en s'y agrafant par ses mandibules, jusqu'à sa mort, après la reproduction quand les fructifications du champignon sortent de la tête de la fourmi en la faisant éclater. Un stipe pousse hors de la fourmi pour ensuite libérer les spores, qui iront contaminer d'autres victimes.
Ophiocordyceps unilateralis et les espèces apparentées sont connus pour s'engager dans un métabolisme secondaire actif, entre autres raisons, pour la production de substances actives en tant qu'agents antibactériens qui protègent l'écosystème hôte-champignon contre une nouvelle pathogenèse pendant la reproduction fongique. En raison de ce métabolisme secondaire, les chimistes des produits naturels s'intéressent à l'espèce, avec la découverte correspondante d'agents à petites molécules (par exemple de la famille des polycétides) présentant un intérêt potentiel pour une utilisation en tant qu'agents immunomodulateurs, anti-infectieux et anticancéreux humains.
Jamur semut atau Ophiocordyceps unliateralis adalah salah satu jenis jamur.
MBank
Jamur semut atau Ophiocordyceps unliateralis adalah salah satu jenis jamur.
Kesalahan pengutipan: Tag tidak sah; tidak ditemukan teks untuk ref bernama MBank
Þessi grein þarfnast yfirlestrar, hér gæti þurft að laga málfar, stafsetningu, og/eða framsetningu.Ophiocordyceps unilateralis er sveppur sem sýkir maura og hefur áhrif á hegðun þeirra.
Náttúrufræðingurinn og landkönnuðurinn Alfred Russel Wallace uppgötvaði sveppinn árið 1859. Hann finnst aðallega í regnskógum. O. unilateralis sýkir maura af Camponotini ættkvíslinni og breytir hegðunarmynstri þeirra. Sýktu hýslarnir fara úr trjánum niður á skógarbotninn, þar er umhverfið heitt og rakt og því hentugt fyrir sveppavöxt. Síðan nota þeir kjálkana til þess að festa sig við stóra æð undir laufblaði, þar sem hýsillin dvelur til dauðadags.[1] Ferlið tekur allt að 4-10 daga.
Orðrétt þýðing tegundaheitsins er „snákshöfuð á þræði, einhliða“, en tegundin á sér ekki íslenskt nafn.
Tegundin þekkist við lok lífferils af æxlunnar uppbyggingu þess, sem samanstendur af mjóum, stæltum og sveigjanlegum dökklitaðum vefstilk sem framlengist frá afturhluta haus dauða maursins. Sveppurinn sýkir maura, mest þektkir sem smíðamaurarnir. Þar sem sveppurinn býr til einn stilk sem rísir á svæðinu fyrir aftan hálsinn þar sem gróberandi kynuppbyggingunni sem eru bornar lárétt. Þegar maurinn er sýktur með sveppnum, mun hann klifra niður úr sínu venjulega búsvæði og bíta niður á neðanverðu laufinu. Þetta er þekkt sem "dauðagripið" og á sér stað á mjög tilteknum stöðum.[2]
Eins og aðrir sveppir sem sýkja skordýr í ættkvíslinni Ophiocordyceps, ræðst O. unilateralis á tiltekna hýsiltegund, Camponotus leonardi maurinn. Hins vegar getur sveppurinn sýkt aðrar náskyldar tegundir af maurum með minni líkum á hýsilstjórn og minni árangri í æxlun.
Sýktir maurar sýna mjög ákveðna hegðun og hafa því verið kallaðir uppvakninga-maurar. Gróin úr sveppunum festir sig og að lokum brýtur í gegn um stoðgrind maursins með þrýstingi og ensímum.[3] Gerstig sveppsins breiðast um í líkama maursins og búa væntanlega til efnasambönd sem hafa áhrif á æðakerfi maursins og nýtir þróunnareinkenni þess að svipfar ætti ekki að vera takmarkað í líffræðilegu ferli eins og prótín nýmyndun eða vefjamyndun, heldur að framlengja það til þess að innihalda öll áhrifin sem erfðavísirinn hefur á umhverfi sitt, til þess að stjórna hegðunnarmynstri sem maurinn sýnir.[4] Sýktur maur sýnir óreglulega tímasetta krampa sem losa það á skógarbotninum.[5]
Sveppurinn finnst aðallega í regnskógum Taílands og Brasilíu.[1]
O. unilateralis er þekkt fyrir að hafa gjöreytt heilum maurabúum. Maurar hafa aftur á móti getuna til þess að skynja það að meðlimur búsinns sé sýktur; heilbrigðu maurarnir bera dauðvona maurana langt í burtu frá þyrpingunni til þess að forðast sveppargró útbreiðslu innan stofnsins.
Ophiocordyceps unilateralis er sveppur sem sýkir maura og hefur áhrif á hegðun þeirra.
Náttúrufræðingurinn og landkönnuðurinn Alfred Russel Wallace uppgötvaði sveppinn árið 1859. Hann finnst aðallega í regnskógum. O. unilateralis sýkir maura af Camponotini ættkvíslinni og breytir hegðunarmynstri þeirra. Sýktu hýslarnir fara úr trjánum niður á skógarbotninn, þar er umhverfið heitt og rakt og því hentugt fyrir sveppavöxt. Síðan nota þeir kjálkana til þess að festa sig við stóra æð undir laufblaði, þar sem hýsillin dvelur til dauðadags. Ferlið tekur allt að 4-10 daga.
Orðrétt þýðing tegundaheitsins er „snákshöfuð á þræði, einhliða“, en tegundin á sér ekki íslenskt nafn.
Ophiocordyceps unilateralis (Tul. & C. Tul.) Petch, 1931[1] è un fungo parassitoide che infetta le formiche, in particolare quelle della specie Camponotus leonardi, alterando il loro comportamento, al fine di garantire la distribuzione capillare delle sue spore. Si tratta di un esempio lampante di parassitismo.[2]
Le formiche vengono infettate tramite gli spiracoli per la respirazione attraverso cui le spore del fungo riescono a raggiungere dei tessuti relativamente deboli e cominciare a svilupparsi. Quando il micelio raggiunge il cervello della formica, ne altera le reazioni ai feromoni gestendo così il comportamento dell'insetto che è in tal modo portato a raggiungere un microclima adatto allo sviluppo del fungo stesso.[3] Un nuovo risultato scientifico indica che il fungo non intacca il cervello ma interagisce solo con i muscoli.[4]
In seguito il fungo determina la morte dell'ospite. Il carpoforo quindi cresce fino a uscire dalla testa dell'insetto e a liberare le spore. Il processo dura dai quattro ai dieci giorni.[2]
Il nome del genere deriva dal greco kordýlē = clava e dal suffisso latino -ceps (da caput, capitis) = capo, testa, ovvero con il capo a forma di clava. L'epiteto specifico unilateralis deriva dal latino e significa "che si sviluppa solamente in un senso".
La specie può essere identificata alla fine del suo ciclo di vita per la sua struttura riproduttiva, costituita da uno stroma, nerboruto ma ancora duttile, di colore scuro, il cui stelo si estende dalla parte posteriore della testa della formica di cui ha provocato la morte. Il fusto ha un ascocarpo appena sotto la punta.[5][6]
Come altri funghi parassitoidi del genere Cordyceps, C. unilateralis mira a specifiche specie come ospiti; queste sono di preferenza le formiche Camponotus leonardi, ma parassitano anche altre specie affini, sebbene con risultati inferiori dal punto di vista riproduttivo.[2]
Quando le formiche si alimentano dei tessuti morbidi non vitali del fungo, alcune spore penetrano nel corpo dell'insetto attraverso gli spiracoli per la respirazione. Vi germinano e quando il fungo parassita è pronto a produrre nuove spore, il suo micelio raggiunge il cervello dell'ospite e determina un'alterazione nella percezione dei feromoni, che porta l'insetto a raggiungere una foglia posta a circa 25 cm di altezza dal suolo, dal lato della pianta rivolto a nord, posta in un ambiente con il 94-95% di umidità e tra i 20 e i 30 °C - condizioni adatte alla riproduzione del fungo. In condizioni differenti, la sporulazione potrebbe non avvenire oppure il fungo potrebbe presentare strutture riproduttive sottodimensionate.[3]
Durante l'infezione il mutamento nelle abitudini della formica ospite è tanto caratteristico da aver dato origine al termine formica zombie,[7] ed è tutto a beneficio del fungo. Raggiunta la sede adatta, l'insetto ospite si àncora alla foglia con un morso. In particolare, la formica infetta morde la nervatura centrale della foglia con una forza superiore al solito, lasciando dei caratteristici segni a forma di manubrio, che sono stati rinvenuti anche su fossili di piante provenienti dal Pozzo di Messel e risalenti a 48 milioni di anni fa.[8][9]
In seguito il fungo determina la morte della formica e continua a crescere nel corpo dell'ospite finché il micelio non invade tutto l'organismo, fermandosi solo di fronte al robusto esoscheletro.[2] I vari miceli sfondano poi la corazza e si consolidano alla pianta su cui si trovano producendo antimicrobici per allontanare la concorrenza.[2] Il carpoforo cresce fino a uscire dalla testa dell'insetto e a liberare le spore. Il processo dura dai quattro ai dieci giorni.[2]
Possono risultare infetti numerosi esemplari di formica e "si possono trovare cimiteri di formiche con venti o trenta cadaveri in un solo metro quadro".[7]
Questo fungo è diffuso in tutte le foreste tropicali, soprattutto in Africa, Brasile e Thailandia.[10]
Non commestibile, senza valore.
Questo fungo contiene vari metaboliti bioattivi e si fanno ricerche per trovare altri impieghi come fonte naturale di sostanze immunomodulatrici, antitumorali, ipoglicemiche e ipocolesterolemiche,[11] sei derivati del naftochinone, uno dei quali ha mostrato in vitro attività antimalarica.[12][13]
C'è anche stata una ricerca sull'uso di pigmenti rossi ottenuti dal naftochinone prodotto da O. unilateralis per usi alimentari, cosmetici e farmaceutici.[14]
«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 before dying.»
(David Hughes)(EN) Ian Sample, 'Zombie ants' controlled by parasitic fungus for 48m years, in guardian.co.uk, Guardian Media Group, 18 agosto 2010. URL consultato il 31 maggio 2011.Ophiocordyceps unilateralis (Tul. & C. Tul.) Petch, 1931 è un fungo parassitoide che infetta le formiche, in particolare quelle della specie Camponotus leonardi, alterando il loro comportamento, al fine di garantire la distribuzione capillare delle sue spore. Si tratta di un esempio lampante di parassitismo.
Le formiche vengono infettate tramite gli spiracoli per la respirazione attraverso cui le spore del fungo riescono a raggiungere dei tessuti relativamente deboli e cominciare a svilupparsi. Quando il micelio raggiunge il cervello della formica, ne altera le reazioni ai feromoni gestendo così il comportamento dell'insetto che è in tal modo portato a raggiungere un microclima adatto allo sviluppo del fungo stesso. Un nuovo risultato scientifico indica che il fungo non intacca il cervello ma interagisce solo con i muscoli.
In seguito il fungo determina la morte dell'ospite. Il carpoforo quindi cresce fino a uscire dalla testa dell'insetto e a liberare le spore. Il processo dura dai quattro ai dieci giorni.
Ophiocordyceps unilateralis is een insectenziekte veroorzakende schimmel die vooral voorkomt bij mieren. Ze wordt vooral aangetroffen in tropische bosecosystemen. De schimmel is alleen schadelijk voor insecten, dus niet voor mensen.
De schimmel werd voor het eerst beschreven door de Britse natuuronderzoeker Alfred Russel Wallace in 1859. Om zijn eigen voorplanting en verspreiding te bevorderen, manipuleert O. unilateralis de gedragspatronen van een besmette mier, specifiek Camponotus leonardi. De besmette mier verlaat zijn nest en foerageergebied, op zoek naar een plek op de bosbodem met een temperatuur en luchtvochtigheid die geschikt is voor de groei van de parasiet. De geïnfecteerde mier zal zich dan met de onderkaak vastklemmen aan de hoofdnerf op de onderkant van een blad en uiteindelijk sterven.
De schimmel kan, aan het einde van zijn levenscyclus, op naam worden gebracht met behulp van het vruchtlichaam ervan, dat bestaat uit een donkergekleurde, pezige doch buigzame stengel (stroma) die uit de achterkant van de kop van de overleden mier treedt. De steel heeft een perithecium (sporendrager) net onder de punt aan het uiteinde van deze stengel.
Van O. unilateralis is bekend dat het hele mierenkolonies kan vernietigen. In reactie hierop zijn de mieren geëvolueerd en hebben manieren ontwikkeld om te herkennen dat een lid van de kolonie besmet is geraakt. Gezonde mieren dragen dan de stervende, besmette mier ver weg van de kolonie om blootstelling aan schimmelsporen te voorkomen.
O. unilateralis kan op zijn beurt door een onbekende schimmelsoort, een zogeheten hyperparasiet (parasiet op een parasiet), worden geïnfecteerd. De hyperparasiet valt de stengel van Ophiocordyceps unilateralis aan op het moment dat deze reproductieve structuur uit het mierenkadaver treedt. Dit kan ervoor zorgen dat het vruchtlichaam van O. unilateralis geen sporen meer kan vrijgeven.
De schimmel komt voor in de tropische bossen van Thailand, en in de regenwouden van Brazilië.
Ophiocordyceps unilateralis is een insectenziekte veroorzakende schimmel die vooral voorkomt bij mieren. Ze wordt vooral aangetroffen in tropische bosecosystemen. De schimmel is alleen schadelijk voor insecten, dus niet voor mensen.
Cordyceps unilateralis (Tul.) Sacc. (1883)
Utbreiing Habitat: Tropisk regnskog SystematikkOphiocordyceps unilateralis er eit kompleks av parasittiske soppartar som snyltar på maur i underfamilien Formicinae.[1] Dei er blitt funne i tropisk regnskog i Thailand[2] og Brasil.[3]
Soppen endrar åtferda til mauren og får han til sist til å bita seg fast på undersida av eit blad på eit tre, stort sett i ei åre på bladet, før han døyr. Ein struktur som kan spreia sporane til soppen veks ut frå hovudet til mauren.[4]
Ophiocordyceps unilateralis er eit kompleks av parasittiske soppartar som snyltar på maur i underfamilien Formicinae. Dei er blitt funne i tropisk regnskog i Thailand og Brasil.
Soppen endrar åtferda til mauren og får han til sist til å bita seg fast på undersida av eit blad på eit tre, stort sett i ei åre på bladet, før han døyr. Ein struktur som kan spreia sporane til soppen veks ut frå hovudet til mauren.
Ophiocordyceps unilateralis (Tul.) Petch − gatunek grzybów z rodziny Ophiocordycipitaceae[1]
Pozycja w klasyfikacji według Index Fungorum: Ophiocordycipitaceae, Hypocreales, Hypocreomycetidae, Sordariomycetes, Pezizomycotina, Ascomycota, Fungi[1].
Po raz pierwszy zdiagnozował go w 1865 r. Ch. Tulasne nadając mu nazwę Torrubia unilateralis. Obecną, uznaną przez Index Fungorum nazwę nadał mu w 1931 r. Petch.
Grzyb potrzebuje odpowiedniej temperatury i wilgotności oraz odległości od gleby do wzrostu. Zarodniki atakują mrówkę. Grzyb rozrastając się zmienia sposób, w jaki reaguje ona na feromony. Zainfekowana ofiara porzuca mrowisko, wchodzi na drzewo i na odpowiedniej wysokości wbija się w liść żuwaczką i obumiera. Grzyb przerasta ciało mrówki i z tyłu jej głowy wypuszcza szypułkę, która, pękając, rozsiewa zarodniki. Zarodniki są niesione z wiatrem i infekują kolejne mrówki.
Pasożyt infekujący mrówki z gatunku Camponotus leonardi, i jak wcześniej sądzono, zmieniający ich zachowanie w celu rozsiania zarodników. Okazało się, że grzyb nie kontroluje mózgu ofiary, lecz przejmuje kontrolę nad mięśniami nóg, czy żuchwy mrówek[3].
Ophiocordyceps unilateralis[1] är en svampart som tillhör divisionen sporsäcksvampar, och som först beskrevs av Louis René Tulasne och Charles Tulasne, och fick sitt nu gällande namn av Thomas Petch. Ophiocordyceps unilateralis ingår i släktet Ophiocordyceps, och familjen Ophiocordycipitaceae.[1] Arten är reproducerande i Sverige.[1]
Svampen angriper myror och förändrar deras beteende. Myran infekteras av sporer när den passerar svampen och efter ett par dagar faller den ner från trädet där den vanligtvis lever och klättrar därefter upp och biter sig fast på ett löv där fukt och temperatur är optimalt för svampen, varefter den dör. Sedan växer svampens mycel inuti myran medan fruktkroppen växer ut från myrans huvud och producerar nya sporer som kan infektera fler myror.
En fiktiv variant av svampen är med i spelet The Last of Us. Infektionen sprider sig till mänskligheten och skapar en zombie-liknande sjukdom, som gör så att de infekterade blir fientliga och våldsamma mot de icke-infekterade, vilket resulterar i ett massivt utbrott som utplånar den största delen av mänskligheten.
Ophiocordyceps unilateralis är en svampart som tillhör divisionen sporsäcksvampar, och som först beskrevs av Louis René Tulasne och Charles Tulasne, och fick sitt nu gällande namn av Thomas Petch. Ophiocordyceps unilateralis ingår i släktet Ophiocordyceps, och familjen Ophiocordycipitaceae. Arten är reproducerande i Sverige.
Svampen angriper myror och förändrar deras beteende. Myran infekteras av sporer när den passerar svampen och efter ett par dagar faller den ner från trädet där den vanligtvis lever och klättrar därefter upp och biter sig fast på ett löv där fukt och temperatur är optimalt för svampen, varefter den dör. Sedan växer svampens mycel inuti myran medan fruktkroppen växer ut från myrans huvud och producerar nya sporer som kan infektera fler myror.
Ophiocordyceps unilateralis, Camponotus leonardi gibi karıncaları enfekte eden bir parazit mantardır. Sporlarının dağıtımı için karıncaların davranışlarını değiştirirler.
Bu tür üretici konumuyla hayat döngüsünün sonunda olduğu tanımlanabilir. Ölen karıncanın kafasının arkasına kadar uzanan bir sırım gibi ama esnek koyu pigmentli stroma sapı oluşturur. Sapın ucunda spor keseleri bulunur.
Diğer böcekleri enfekte eden patojenik mantarlar, Ophiocordyceps sınıfındakiler, (ideal olarak Camponotus leonardi karıncaları) konak bulmaktır. Fakat O. unilateralis karıncaları enfekte eden diğer patojeniklerden daha az bilinirler ve daha az derecede konak manipulasyonuna ve üreme başarısına sahiptirler. Mantarın sporları, cansız olan yumuşak dokuları tüketmeye başladığı böceğin trakeasından içeriye girer. Sporlar hazır olduğunda, miselyumlar karıncanın beynine girip karıncanın farklı algılamasını sağlayarak, onu bir bitkinin gövdesine tırmandırıp, çenesini kullanarak bitkiden korunmaya iter. Enfekte karınca yaprak damarlarını anormal bir kuvvetle ısırır ve dambl şekilli izler bırakır. 48 milyon yıl önce, bitki fosili içindeki araştırmada aynı izlerin Messel oyuğunda görüldüğü tespit edilmiştir.
Ophiocordyceps unilateralis, Camponotus leonardi gibi karıncaları enfekte eden bir parazit mantardır. Sporlarının dağıtımı için karıncaların davranışlarını değiştirirler.
Грибок зустрічається в тропічних лісах Таїланду[3], а також тропічних лісах в Бразилії[4].
Точно незрозуміло, яким саме способом спори гриба потрапляють всередину мурахи. Швидше за все зараження відбувається через пори в клітинах, або через кутикулу. Спори кордицепсу після попадання всередину організму починають активно в ньому розмножуватися і поширяться по всьому тілу мурашки. Імовірно, спори гриба формують активні хімічні сполуки, які і впливають на мозок мурашки, змінюючи його поведінку.
Мураха покидає свою колонію і спускається на землю (цей вид мурах живе на деревах). Комаха вибирає невисоку травинку, залазить на неї і дуже міцно закріплюється за центральну жилку листа. Мураха з максимальною силою хапається за рослину потужними щелепами і ні вітер, ні дощ не може зіштовхнути його. Після цього мураха повністю втрачає контроль над своїм тілом і більше не рухається. Вона ще не вмерла, але вже нічого не може зробити.
Поступово грибок вбиває мурашку, а сам продовжує зростати. Його коріння вже проникли в м'які тканини комахи, пройшли крізь все тіло і надійно закріпилися на листі. Тепер все що залишилося від мурахи — це велика грибниця кордіцепсу однобокого. Відразу ж гриб починає виробляти сильний протимікробний препарат, щоб убезпечити себе від дрібних падальників. Коли гриб надійно зафіксувався, він проростає вгору через голову мурашки. Процес зростання займає 4-10 днів.
Зміни в поведінці заражених мурах дуже специфічні. Інфікованих комах називають «мурашками-зомбі». Вони страждають від сильних судом, через які падають з дерев і не можуть знайти дорогу до свого гнізда. Інстинктивно прагнучи наверх мурахи залазять на невисокі рослини і траву, де знаходять свій останній притулок. Якщо ж тварина не може забратися на траву, то гриб перестає рости, або зростання супроводжується різними аномаліями. Але тварина гине в кожному разі.
Кордицепс однобокий здатний знищити цілу колонію мурах. Комахи виробили здатність відчувати заражених побратимів і виганяти їх зі своєї колонії. Якщо грибок проникає в гніздо, то зараженого мурашку відтягують подалі, щоб вся сім'я не загинула від епідемії. Середня щільність зараження грибком — 20-30 особин на м².
Кордицепс однобокий містить різні відомі і невикористані біологічно активні метаболіти, і досліджується як нове джерело препаратів з імуномодулюючими, протипухлинними, протидіабетичними і гіпохолестеринемічними властивостями.
Nấm sát thủ hay Nấm điều khiển não kiến (danh pháp hai phần: Ophiocordyceps unilateralis) là một loài nấm sống ký sinh trên những xác kiến trong rừng rậm nhiệt đới ở Brasil. Loài nấm ký sinh này có khả năng xuyên vào não bộ của kiến, sau đó giết chết con vật và rồi chui vào trong cơ thể con kiến để phát triển và phát tán các bào của nấm từ đó biến vật chủ thành những xác chết biết đi trước khi giết chúng.
Khi xâm nhập vào cơ thể vật chủ, nấm sử dụng hóa chất đặc biệt để kiểm soát hành vi của kiến. Nấm sẽ "ra lệnh" buộc kiến rời đàn và cắn thủng phần mặt dưới của một chiếc lá. Đến khi bị nấm kết thúc cuộc đời, xác kiến vẫn cắm chặt vào phần thân lá. Cuối cùng, nấm sát thủ sẽ sản sinh một cái cuống dài, đâm xuyên đầu kiến và nhô ra ngoài, bắt đầu phun bào tử để săn con mồi khác, ngoài ra nó còn mọc thêm những cuống nhỏ hơn ở các phần cơ thể kiến, trong đó có bàn chân và khớp chân dưới của kiến (tương tự như khớp gối ở người).
Tuy nhiên một số loài kiến như loài kiến Camponotus rufipes ở rừng mưa nhiệt đới Brazil và kiến thợ mộc ở Thái Lan đã cố gắng bảo vệ các thành viên trong bầy bằng cách chải chuốt cho nhau khiến nấm sát thủ không thể sinh sôi thêm bào tử để hại thêm nhiều kiến khác do vậy dù rất nguy hiểm nhưng nấm sát thủ vẫn bị giới hạn khả năng lây lan và cộng đồng kiến này được bảo toàn.[1]
Nấm sát thủ hay Nấm điều khiển não kiến (danh pháp hai phần: Ophiocordyceps unilateralis) là một loài nấm sống ký sinh trên những xác kiến trong rừng rậm nhiệt đới ở Brasil. Loài nấm ký sinh này có khả năng xuyên vào não bộ của kiến, sau đó giết chết con vật và rồi chui vào trong cơ thể con kiến để phát triển và phát tán các bào của nấm từ đó biến vật chủ thành những xác chết biết đi trước khi giết chúng.
Ophiocordyceps unilateralis
(Tul.) Sacc., 1883
Кордицепс однобокий[2] (лат. Ophiocordyceps unilateralis) — вид грибов, паразитирующих на муравьях-древоточцах вида Camponotus leonardi. Распространён в тропических лесах[3].
Особенность этого гриба в том, что он изменяет поведение организма-хозяина, проявляя так называемую адаптивную манипуляцию паразита. Через 2—3 недели после попадания гриба в организм заражённый муравей уходит из колонии, забирается на высоту около 30 см северной части растения и закрепляется на листе, впиваясь челюстями в жилку — грибы тем самым обеспечивают себе наилучшее положение для распространения спор. После смерти муравья гриб прорастает сквозь всё его тело, а из головы вырастает красно-коричневое плодовое тело[4]. Умершие муравьи продолжают распространять споры гриба, а кутикула муравья становится как бы защитным футляром для паразита. Причём гриб вырастает в два раза больше, чем длина муравья, после чего приступает к половому размножению. Для такого манипулирования поведением кордицепс однобокий образует внутри тела муравья сложную клеточную сеть, которая оплетает все внутренние органы и на химическом уровне контролирует каждый уголок его организма, но при этом, что интересно, не проникает в центральную нервную систему хозяина[5].
Паразитические грибки этого вида ещё 48 млн лет назад управляли поведением муравьёв, о чём говорит окаменелость, найденная на территории бывшего немецкого карьера Мессель[6][7].
Кордицепс однобокий (лат. Ophiocordyceps unilateralis) — вид грибов, паразитирующих на муравьях-древоточцах вида Camponotus leonardi. Распространён в тропических лесах.
偏側蛇蟲草菌（学名：Ophiocordyceps unilateralis）是一种拟寄真菌，俗稱「喪屍真菌」[2]，主要以莱氏屈背蚁（Camponotus leonardi）或弓背蟻屬为寄主。偏侧蛇虫草菌感染蚂蚁後，会控制蚂蚁的肌肉，利用蚂蚁的身体帮助真菌找到适合的生长环境。[3] 当蚂蚁感染了这种真菌，就會離開位於樹冠層的巢穴或是覓食路徑，來到溫度與濕度較適合真菌生長的位置。尋一片葉片後，於葉背以大顎緊緊鉗住葉脈直至死亡，這通常需要花費4~10天。而這段時間也是真菌的生殖階段，子實體從寄主的頭部長出，破裂並釋放孢子。
偏側蛇蟲草菌反過來其實也受到他種真菌的寄生威脅，這一定程度地減少了他對寄主蟻群的破壞。而也因如此偏側蛇蟲草菌發展出能夠釋放具有抗菌效果的次級代謝物的能力，這引起一些科學家的興趣，進而發現了一些有潛力成為免疫抑制劑，抗感染藥劑以及抗癌藥劑的小分子物質(例如聚酮化合物)。
有時偏側蛇蟲草菌的學名會寫成Ophiocordyceps unilateralis sensu lato，其義為「廣義上的」。這是因為該物種是由許多屬於O. unilateralis 的近似物種所組成。
該物種可藉由於生命週期末期所產生的生殖構造進行分類，包括自螞蟻頭部後方延伸而出的深色柔韌子座，逾期尖端下方有一個子囊殼。這種真菌會感染螞蟻，最常見的是大黑蟻，真菌會在他們的背板處生長出柄狀構造來承載他們的產孢器。一旦螞蟻感染了真菌，他們就會離開正常的棲息地並且咬住葉子的葉背，這個現象被稱為「死亡嚙咬」，只出現在特定的地區。
如同他種Ophiocordyceps 屬的蟲生真菌，偏側蛇蟲草菌對於寄生的物種也具有一定的專一性，那就是Camponotus leonardi 這種螞蟻。當然他們也會寄生在與其親緣關係較近的螞蟻種類身上，但是繁殖與寄生的成功率較低。
受感染的螞蟻行為相當特殊，甚至產生了一種流行術語「殭屍螞蟻」，當然這種行為為真菌帶來了益處。寄生的過程是這樣的，真菌的孢子附著後會利用酵素突破螞蟻的外骨骼。進入螞蟻體內後，真菌開始擴散，並且釋放一種可以影響螞蟻血腔的化合物，接著取得螞蟻的身體控制權。被感染後的螞蟻會產生不定時的抽搐並設法移動到森林底層。螞蟻會爬上植物的莖，用下顎以異常的力量將自己固定在葉脈上，並留下一個啞鈴狀的痕跡，其平均高度為森林地面上方25.20±2.46公分，位於植物北側，濕度約為94-95％，溫度為20至30°C的環境（68和86°F）。
感染可能導致每平方米20至30隻螞蟻的死亡。每每它們都在離地面特定高度的樹葉上死亡，並且緊緊地咬著葉脈。當死去的螞蟻被移除時，該真菌的生長和孢子皆失敗或產生異常。根據植物化石數據庫的搜索顯示，4800萬年前德國的梅塞爾坑的化石葉上就已經有類似的啞鈴狀痕跡。
一旦螞蟻的大顎咬住葉脈，真菌就會開始破壞螞蟻的肌肉組織，並減少粒線體和內質網的數量。這讓螞蟻不再能控制大顎的肌肉並保持固定，這個行為在真菌的生命週期中扮演著非常重要的角色。
接著真菌殺死螞蟻，繼續生長，它的菌絲逐漸侵入螞蟻的軟組織，並在結構上加強其外骨骼。然後更多的菌絲體從螞蟻中生長出來，並將其牢牢地固定在植物上，同時分泌抗菌藥物以贏得生存競爭。當真菌準備繁殖時，它的子實體會從螞蟻的頭部生長並破裂，並釋放出孢子。 這個過程需要四到十天。
綜觀整個生命週期，他們有著獨特的代謝活動來應對獨特的挑戰，真菌孢子必須牢固地附著並穿透節肢動物的外骨骼，接著避過或抑制宿主的防禦，然後，在殺死宿主之前控制他的行為; 最後，它必須保護宿主屍體免受微生物和食腐者的攻擊。
此種真菌主要分布於泰國和巴西的熱帶雨林中。
偏側蛇蟲草菌有能力毀掉整個蟻群，相對地，螞蟻也有能力感應出哪個巢穴中的同伴已經被感染。為避免更大的災害，他們會將垂死的同伴帶離巢穴。
Ophiocordyceps 屬的蟲生真菌含有各種已知的或是非典型的代謝物質，這些天然產物被發現擁有成為免疫調節，抗腫瘤，降血糖和降膽固醇標靶藥劑的潛力。
目前已經從偏側蛇蟲草菌中分離出六種已知的萘醌化合物，即紅黴素，脫氧胸苷，4-O-甲基紅黴素，表甲硫基甾醇，脫氧甲基甾醇和3,5,8-三羥基-6-甲氧基-2-（5-氧代己-1-， 3-二烯基）-1,4-萘醌，其中最後一個在與研發抗瘧疾藥物相關的體外試驗中顯示出活性。
由偏側蛇蟲草菌製成的紅色萘醌顏料，在酸性條件下顯示紅色，在鹼性條件下顯示紫色。這些顏料在酸/鹼環境下非常穩定，明亮且無細胞毒性，這使得它們適用於食品著色以及其他材料的染色。這些特性也使其成為結核病患者抗結核藥物檢測的首選藥物，通過與化療藥物聯合改善症狀和增強免疫力。
偏側蛇蟲草菌有一種不明的寄生性真菌天敵，那些天敵被稱為「抗殭屍真菌真菌」，寄生者會在偏側蛇蟲草菌釋放孢子前進入螞蟻的屍體中攻擊他，這導致了被寄生的偏側蛇蟲草菌只有6-7％的孢子囊存活，限制了偏側蛇蟲草菌對螞蟻族群的破壞。螞蟻會培養這種偏側蛇蟲草菌的天敵以達成互利共生。
偏側蛇蟲草菌（学名：Ophiocordyceps unilateralis）是一种拟寄真菌，俗稱「喪屍真菌」，主要以莱氏屈背蚁（Camponotus leonardi）或弓背蟻屬为寄主。偏侧蛇虫草菌感染蚂蚁後，会控制蚂蚁的肌肉，利用蚂蚁的身体帮助真菌找到适合的生长环境。 当蚂蚁感染了这种真菌，就會離開位於樹冠層的巢穴或是覓食路徑，來到溫度與濕度較適合真菌生長的位置。尋一片葉片後，於葉背以大顎緊緊鉗住葉脈直至死亡，這通常需要花費4~10天。而這段時間也是真菌的生殖階段，子實體從寄主的頭部長出，破裂並釋放孢子。
偏側蛇蟲草菌反過來其實也受到他種真菌的寄生威脅，這一定程度地減少了他對寄主蟻群的破壞。而也因如此偏側蛇蟲草菌發展出能夠釋放具有抗菌效果的次級代謝物的能力，這引起一些科學家的興趣，進而發現了一些有潛力成為免疫抑制劑，抗感染藥劑以及抗癌藥劑的小分子物質(例如聚酮化合物)。
