Cordyceps is a genus of sac fungi known as ascomycete fungi that includes about 400 species. All Cordyceps species are mainly parasitic on insects and other arthropods; a few are parasitic on other fungi. The generic name Cordyceps is derived from the Greek word kordyle, meaning “club”, and the Latin stem -ceps, meaning “head”. Several species of Cordyceps are considered to be medicinal mushrooms in traditional Chinese and Tibetan medicines. In the 15th Century a Tibetan text “An Ocean of Aphrodisical Qualities” advocated the use of the fungi.
Isaria sinclairii, previously known as Cordyceps sinclairii, is a fungus which attacks insects, including cicada. It is a species of entomopathogenic fungi. It produces myriocin, from which the synthetic drug fingolimod or Gilenya, a treatment for multiple sclerosis, was developed. The larvae typically die just beneath the soil surface and the fungus produces white tufts which grow up from the soil and release powdery white spores.
Species related to Isaria sinclairii, such as Yartsa gunbu Ophiocordyceps sinensis, have been used in traditional Tibetan medicine and in traditional Chinese medicine as tonics, which some refer to as an elixir of eternal youth.
When a Cordyceps fungus attacks a host, the mycelium invades and eventually replaces the host tissue, while the elongated fruit body (ascocarp) may be cylindrical, branched or of complex shape. The ascocarp bears many small, flask-shaped perithecia containing asci, made up of thread-like ascospores, which usually break into fragments and are presumably infective. Some current and former Cordyceps species are able to affect the behaviour of their insect host, for example Ophiocordyceps unilateralis causes ants to climb a plant and attach there before they die thereby ensuring the parasite’s environment is at an optimal temperature and humidity, and that the spores from the fruit body that sprout out of the dead insect are distributed. Marks have been found on fossilised leaves that suggest this ability to modify the host’s behaviour evolved more than 48-million years ago.
The genus has a worldwide distribution and most of the approximately 400-species have been described from Asia. Cordyceps species are particularly abundant and diverse in humid temperate and tropical forests.
Some Cordyceps species are sources of biochemicals with interesting biological and pharmacological properties. Cordycepin was the source of Cyclosporin—an immunosuppressive drug helpful in human organ transplants by inhibiting rejection.
Even the smallest micro-organisms have a function within the ecosystem and are important in regulating the ecological balance of nature.