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Vegetable caterpillar

Caterpillar fungus, Vegetable Caterpillar or Yarsagumba is a Chinese medicine product that is a result of a parasitic relationship between a Cordyceps fungus and a caterpillar, (usually Thitarodes) found in southwestern mountains of China. As the fungi invades, it grows off larvae and the end result is desiccated caterpillar shell, with a fungal fruiting body attached. It is known in the West primarily from its use in Traditional Chinese medicine, where it is a prized ingredient.

Names

In Tibetan it is known as Yartsa Gunbu [Wylie: dbyar rtswa dgun 'bu], source of Nepali:यार्सागुम्बा, Yarshagumba, Yarchagumba. It is also known as keera jhar or keeda ghas in India. Its name in Chinese "dong chong xia cao" (冬虫夏草) means "winter worm, summer grass" (meaning "worm in the winter, (turns to) plant in the summer"). The Chinese name is a literal translation of the original Tibetan name, which was first recorded in the 15th Century by the Tibetan doctor Zurkhar Namnyi Dorje (Wylie: Zur mkhar mnyam nyid rdo rje’s [1439-1475]) in his text: Man ngag bye ba ring bsrel (Oral Instructions on a Myriad of Medicines).

The name 'vegetable caterpillar' is a clear misnomer. Caterpillar fungus is a preferable term.

In traditional Chinese medicine, its name is often abbreviated as "chong cao", a name that also applies to other Cordyceps species, such as C. militaris.

Strangely, sometimes in Chinese English language text Cordyceps sinensis is referred to as 'Aweto', which is the Maori name for a different Cordyceps species from New Zealand. In Japanese it is known as tochukaso/tohchukaso.

Natural history

The caterpillar prone to infection by the fungus lives underground in alpine grass and shrublands on the Tibetan Plateau and the Himalayas at an altitude between 3000m and 5000m. Spending up to five years underground before pupating, the caterpillar is attacked while feeding on roots. The fungus invades the body of the Thitarodes caterpillars, filling its entire body cavity with mycelium and eventually killing and mummifying it. The caterpillars die near the tops of their burrows. The dark brown to black fruiting body (or mushroom) emerges from the ground in spring or early summer, always growing out of the forehead of the caterpillar. The long, usually columnar fruiting body reaches 5-15 cm above the surface and releases spores.

In Nepal caterpillar fungus is found on the subalpine pastures in Dolpo in Karnali Zone and Darchula in mahakali zone. It is also common in Bhutan and India's Himachal Pradesh. Reports from distribution outside of High Asia are probably erroneous and relate to other species of Cordyceps, e.g. Cordyceps militaris.

It is not certain how the fungus infects the caterpillar; possibly by ingesting a fungal spore or by the fungus mycelium invading the insect through one of its breathing pores.

It is also found in Nandadevi centuary in Uttarakhand Himalayas of India. In the onset of Summer grasslands of Delisera, Dharansi, Malari are populated by the local people, who can be seen crouching on the ground and looking for the "Kira Jari" or the caterpillar root. The locals clean this fungus, dry it and sell it at 100 - 150 rupees (Indian currency) each.

Because of its rarity and value, inter-village conflicts over the grasslands has become a headache of the local governing bodies.

Use in Medicine

Traditional Chinese medicine

The first mention of Cordyceps sinensis in traditional Chinese Medicine was in the 18th Century.

The entire fungus-caterpillar combination is hand-collected for medicinal use.

The fungus is highly prized by practitioners of Tibetan medicine, Chinese medicine and traditional herbal Folk medicines, in which it is used as an aphrodisiac and as a treatment for a variety of ailments from fatigue to cancer. It is regarded as having an excellent balance of yin and yang as it is apparently both animal and vegetable (though it is in actuality not vegetable, but fungal). Assays have found that Cordyceps species produce many pharmacologically active substances. They are now cultivated on an industrial scale for their medicinal value.

The popularity of this fungus recently grew because two female Chinese athletes, Wang Junxia and Qu Yunxia, who beat the world records for 1500, 3000 and 10,000 meters in 1993 in Stuttgart, were reported to have used Cordyceps at the recommendation of their coach. However, this version of the events that lead to the extraordinary records of the Chinese women's team was regarded as a smoke screen by many doping experts. Interestingly, the Chinese athletes could not repeat their performance in the following years, indicating further that illegal doping might have been involved.

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; the typical dosage is 3-9 grams.

Treatment of radiation poisoning

Some work has been published in which Cordyceps sinensis has been used to protect the bone marrow and digestive systems of mice from whole body irradiation.

Economics and impact

Its value gave it a role in the Nepalese Civil War, as the Nepalese Maoists and government forces fought for control of the lucrative export trade during the June - July harvest season. Collecting yarchagumba in Nepal had only been legalised in 2001, and now demand is highest in countries such as China, Thailand, Korea and Japan. By 2002, the herb was valued at R 105,000 ($1,435) per kilogram, allowing the government to charge a royalty of R 20,000 ($280) per kilogram.

In Tibet, Yartsa Gunbu developed to become the most important source of cash income in rural Tibet. Prices are increasing continuously, especially since the late 1990s. In 2007, one kg traded for US$3000 (lowest quality) to over US$15,000 (best quality equalling the largest larvae).

The search for Cordyceps sinensis is often perceived to pose a threat for the environment of the Tibetan Plateau where it grows. However, it has been collected for centuries and is still common in such collection areas. However, current collection rates are much higher than in historical times.

Cordyceps producers like to perpetuate the story that unscrupulous harvesters insert twigs into the stromata of wild C. sinensis to increase the weight and therefore the price paid. Tiny twigs are only used when the stromata is broken from the caterpillar, and has nothing to do with weight increases. Supposedly at some point in the past, someone has inserted lead wires with which to increase weight, however, each year hundreds of millions of specimens are harvested and this appears to have been a one time occurrence.

Cultivated C. sinensis mycelium is a sustainable alternative to wild-harvested C. sinensis, and producers claim it may offer improved consistency. Artificial culture of C. sinensis is typically by growth of the pure mycelium in liquid culture (in China) or on grains (in the West). Stromata are not produced apart from the insect host.

References

WINKLER, D. 2005. Yartsa Gunbu - Cordyceps sinensis. Economy, Ecology & Ethno-mycology of a Fungus Endemic to the Tibetan Plateau. In: A.BOESI & F. CARDI (eds.). Wildlife and plants in traditional and modern Tibet: Conceptions, Exploitation and Conservation. Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, Vol. 33.1:69-85.