Ophiocordyceps sinensis, formerly Cordyceps sinensis and colloquially known as caterpillar fungus, is an insect-pathogenic fungus in the family Ophiocordycipitaceae. It is primarily found in high-altitude regions of the Tibetan Plateau. It parasitizes larvae of ghost moths and produces a fruiting body which is valued in traditional Chinese medicine and Nepalese medicine as an aphrodisiac. However, naturally harvested fruiting bodies often contain high amounts of arsenic and other heavy metals, making them potentially toxic. As a result, their sale has been strictly regulated by China's State Administration for Market Regulation since 2016. O. sinensis parasitizes the larvae of moths within the family Hepialidae, specifically genera found on the Tibetan Plateau and in the Himalayas between elevations of 3,000–5,000 m (9,800–16,400 ft). found across Tibet, the Himalayan regions of India, Bhutan and Nepal, and several Chinese provinces (Qinghai, Sichuan, and Yunnan). The fungus germinates in the living larva, kills and mummifies it, and a fruiting body emerges from the corpse as an upright stalk. O. sinensis is classified as a medicinal mushroom, and its use has a long history in traditional Chinese medicine as well as in traditional Tibetan medicine. It is marketed for various health benefits but lacks sufficient scientific evidence for safety or effectiveness, and quality can vary due to inconsistent processing and labeling. The hand-collected, intact fungus-caterpillar body is valued by herbalists as medicine, and because of its cost, its use is also a status symbol. The fruiting bodies of the fungus are not cultivated commercially outside of China, but the mycelium form can be cultivated in vitro. Overharvesting and overexploitation have led to the classification of O. sinensis as an endangered species in China. Additional research needs to be carried out in order to understand its morphology and growth habits for conservation and optimum utilization.
Taxonomic history and systematics
Morphological features Ophiocordyceps sinensis consists of two parts, a fungal endosclerotium (within the caterpillar) and stroma. The stroma varies from dark brown or black, but can be a yellow color when fresh, and longer than the caterpillar itself, usually 4–10 cm. It grows singly from the larval head, and is clavate, sublanceolate or fusiform, and distinct from the stipe (stalk). The stipe is slender, glabrous, and longitudinally furrowed or ridged. The fertile part of the stroma is the head. The head is granular because of the ostioles of the embedded perithecia. The perithecia are ordinally arranged and ovoid. The asci are cylindrical or slightly tapering at both ends, and may be straight or curved, with a capitate and hemispheroid apex, and may be two to four spored. Similarly, ascospores are hyaline, filiform, multiseptate at a length of 5–12 μm and subattenuated on both sides. Perithecial, ascus and ascospore characters in the fruiting bodies are the key identification characteristics of O. sinensis. Ophiocordyceps species produce whole ascospores and do not separate into part spores. This is different from other Cordyceps species, which produce either immersed or superficial perithecia perpendicular to stromal surface, and the ascospores at maturity are disarticulated into part spores. Generally, Cordyceps species possess brightly colored and fleshy stromata, but O. sinensis has dark pigments and tough to pliant stromata, a typical characteristic feature of most of the Ophiocordyceps species.
Developments in classification
The species was first described scientifically by Miles Berkeley in 1843 as Sphaeria sinensis. The species was later reclassified Cordyceps in 1878 by Pier Andrea Saccardo. The fungus was known as Cordyceps sinensis until 2007, when molecular analytical techniques were used to amend the classification of Cordycipitaceae and Clavicipitaceae, resulting in the naming of a new family Ophiocordycipitaceae and the reclassification of several Cordyceps species, including C. sinensis, to the genus Ophiocordyceps.
Common names In Tibet, it is known as yartsa gunbu, དབྱར་རྩྭ་དགུན་འབུ་ (Wylie: dbyar rtswa dgun 'bu, ZWPY: yarza g̈unbu, Lhasa dialect: [jɑ̀ːt͡sɑ kỹ̀pu], "summer grass winter worm"). The name was first recorded in the 15th century by the Tibetan doctor Zurkhar Namnyi Dorje. In colloquial Tibetan, yartsa gunbu is often shortened to "yartsa" or "bu". The Tibetan name is transliterated in Nepali as यार्चागुन्बू, यार्चागुन्बा, yarshagumba, yarchagumba or yarsagumba. The transliteration in Bhutan is yartsa guenboob. In India, it is known as keera jhar, keeda jadi, keeda ghas or ghaas fafoond in Nepali, Hindi and Garhwali. It is known in Chinese as dōng chóng xià cǎo (冬蟲夏草), meaning "winter worm, summer grass", which is a literal translation of the original Tibetan name. In traditional Chinese medicine, its name is often abbreviated as chong cao (蟲草 "insect plant"), a name that also applies to other Cordyceps species, such as C. militaris. In Japanese, it is homophonically read as tōchūkasō (冬虫夏草), while in Korean and Vietnamese it is known by the transliterated forms of the Chinese word, dongchunghacho (동충하초) and đông trùng hạ thảo respectively. Some Chinese English-language texts refer to Cordyceps sinensis as āweto, which is the Māori name for Ophiocordyceps robertsii, a species from south-eastern Australia and New Zealand. The English term "vegetable caterpillar" is a misnomer, as no plant is involved. "Caterpillar fungus" is a preferred term.
Synonyms Since the 1980s, 22 species in 13 genera have been attributed to the anamorph (asexually reproducing mold-like form) of O. sinensis.
Additional synonyms for the teleomorph are Cordyceps nepalensis and C. multiaxialis. They have similar morphological characteristics to O. sinensis, also had almost identical or identical ITS sequences and its presumed anamorph, H. sinensis.
Ecology and life cycle
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