Ophiocordyceps sinensis

Ophiocordyceps  sinensis

Ophiocordyceps  sinensis is found primarily on the Tibetan Plateau and is endemic to alpine regions. The fungus parasitizes and

mummifies the larva of several ghost moth species to form a fungus caterpillar complex. This complex has been widely used in traditional Chinese to treat a wide variety of ailments including asthma and respiratory inflammation. The increase in commercial demand has led to excessive harvest and an extreme decline in the natural population; Ophiocordyceps sinensis is currently listed as an endangered species in China.

  

The life cycle of O. sinensis can be divided into teleomorphic and anamorphic stages The anamorphic stage results from the teleomorphic stage; molecular studies of microcycle conidation from ascopores have determined Hirsutella sinensis as the species for the asexual stage. 

The fungus must infect a host insect in order to enter the teleomorphic, or sexual stage. The host insect species is a

subterranean, root boring insect that lives above altitudes of 3000m on the Tibetan Plateau. Ghost moth larvae of the

genus Hepialus  seem to be the most common hosts, although other potential hosts have been identified.

  

Thitarodes moth, a host species of Ophicordycesp sinensis

Clinical trials have demonstrated that O. sinensis can potentially induce apoptosis in cancerous cells. Secondary bioactive metabolites have also been isolated from fungal species other than O. sinensis that live on the funguscaterpillar complex.

Various pipolythiodioxopiperazines (ETPs) have been determined to inhibit proliferation and induce apoptosis of cancerous cells in immunodeficient mice . Other molecules such as diketopiperazines have been found to be cytotoxic against cancerous cells . The presence of these metabolites seem to support the traditional medicinal qualities of the  fungus caterpillar complex. However, other studies have shown that O. sinensis potentially contains agents that could inhibit apoptosis, and lead to cancer formation. The results of these studies are not yet comprehensive, and much is unclear about the specific mechanisms by which O. sinensis acts as a medicinal agent. Thus, more research is needed to conclusively determine the medicinal effects of naturally occurring O. sinensis on the human body.

O. sinensis is one of the most valuable medicinal fungi in the world;the price has been rising in recent years, and currently it is worth more than its weight in gold. Sales of naturally occurring O. sinensis specimen represent an important part of the GDP of local governments. 80% of families in major production areas collect caterpillar fungi, and this business comprises 50%

of their total income. 

the source of many important rivers in Asia, and its ecological fate affects many other environments. O. sinensis is found mainly on the Tibetan Plateau, but has also been documented in other Himalayan countries such as Nepal, Bhutan, and India.

ScarletCaterpillarFungus-Cordycepsmilitaris

The spread of O. sinensis depends on the shooting of ascospores from the fruiting bodies; this is limited to defined areas on the mountains, and the gene flow between various different populations is expected to be low. The need for O. sinensis to parasitize underground larvae, as well as its  psychrophilic  nature also limit the spread of the species to other environments.

O. sinensis is part of a tripartite relationship between the fungal species, the host insect it infects, and the plants that the

insect consumes. This relationship seems to maintain itself in a relatively stable system.

 However, overharvesting thevaluable funguscaterpillar complex leads to a decrease in the fungal spores that are released, and an increase in the host insect population.  

Ghost moths in particular have been known for their ability to destroy plant populations in some ecosystems . It is largely unknown how the increase in the ghost moth population, and the following increase in herbivory could alter the plant community in the Tibetan Plateau.

The fungus infects the underground larva in late autumn. Infection rates are highest in the 4th to 5th instar larvae that are shedding old cuticles and forming new ones. Less advanced larvae are less likely to be infected because they exhibit limited movement and food uptake, whereas larvae that have passed the 5th instar stage have increased resistance to fight the fungal infection. This stage in the larval life cycle overlaps temporally with the release of spores by O. sinensis. 

The mycelia enter the hemocoel of the larva, fragment into fusiform hyphae, and multiply by yeasttype budding to fill

the hemocoel. The infected larva moves to 25 cm below the surface of the soil and dies with the head facing upward. The fungus grows out of the head of the insect host to form a stroma bud that freezes in the winter. In the spring, the stroma bud grows to emerge above the soil surface and form the stalked fruiting body.  

Other factors influence the infection rate of O. sinensis. The presence of other specific fungal species shortens the time

required to mummify the host larva from 50 days to 35

days. This increases the infection rate from 3% to 60%. Infection

is facilitated by loose soil and precipitation that allow the movement of ascospores deeper into the soil to be more accessible to the larva. Infection rates increase when large differences between day and night temperature increase the vertical movement of the larva.