Cordyceps

Cordyceps is a genus of ascomycete fungi that includes thousands of species. The species that parasitizes the vegetable caterpillar &mdash; Cordyceps sinensis &mdash; is the most famous of these, having long been considered a precious ingredient in Chinese traditional medicines.

All Cordyceps species are parasitic, mainly on insects and other arthropods (they are thus entomopathogenic fungi); a few are parasitic on other fungi like the subterranean, truffle-like Elaphomyces. The mycelium invades and eventually replaces the host tissue, while the elongated fruiting body (stroma) may be cylindrical, branched, or of complex shape. The stroma bears many small, flask-shaped perithecia that contain the asci. These in turn contain the thread-like ascospores, which usually break into fragments and are presumably infective.

The genus has a worldwide distribution and most species have been described from Asia (notably China, Japan, Korea and Thailand). The genus has many anamorphs (asexual states), of which Beauveria (possibly including Beauveria bassiana), Metarhizium, and Isaria) are the better known, since these have been used in biological control of insect pests. 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, like cordycepin; the anamorph of Cordyceps subsessilis (Tolypocladium inflatum) was the source of ciclosporin &mdash; a drug helpful in human organ transplants, as it suppresses the immune system (Immunosuppressive drug).

Cordyceps sinensis
Cordyceps sinensis is a species of fungus found in southwest, mountainous China that attacks caterpillars, specifically the larvae of hepialid moths (identified as species of Hepialus or Thitarodes). The caterpillars feed on the roots of trees and shrubs on the slopes of the Himalayas. When infected by C. sinensis, the bug's entire body cavity is filled by the fungus mycelium, killing the host, and the caterpillars die near the tops of their burrows. A dark brown, finger-like stroma sprouts near their heads. The entire fungus-caterpillar combination is hand-collected for medicinal use.

According to Bensky (2006), laboratory-grown C. sinensis mycelium has similar clinical efficacy and less associated toxicity. He notes a toxicity case of constipation, abdominal distension, and decreased peristalsis, two cases of irregular menstruation, and one case report of amenorrhea following ingestion of tablets or capsules containing C. sinensis. In Chinese medicine C. sinensis is considered sweet and warm, it enters the Lung and Kidney channels, and the typical dosage is 3-9 grams (Bensky 2006).



In China C. sinensis has been called "Dong Chong Xia Cao," which can be translated "winter worm summer grass." It is also known as Aweto in China and Tibet, and as Yarchagumba in Tibet. In English it is often called "caterpillar fungus" or "vegetable worm."

The excessive collecting of Cordyceps sinensis for sale in traditional medicine poses a threat for the environment of the Tibetan plateau where it grows. The high price of wild C. sinensis has led unscrupulous harvesters to insert twigs or even lead wires into the stromata, thereby increasing the weight and price paid. Cultivated C. sinensis mycelium is a more sustainable alternative to wild-harvested C. sinensis, and may offer improved consistency. Artificial culture of C. sinensis is typically by growth of the pure mycelium in liquid culture--stromata are not produced apart from the insect host.