The Wonderful World of Fungi

Part XI – Division Ascomycota- Fascinating Members (Cordyceps) – Fascinating Members (Morels)

By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter
AAAC Collection Station—Birmingham, Alabama

Cordyceps ascocarps.

If you are one of those people who enjoys watching movies about zombies or reading about them, then you should like reading about Cordyceps, Ophiocordyceps, and related fungi. Common names for these fungi include the English name caterpillar fungus, the Tibetan name yartsa gunbu, and the Chinese name dong chong xia cao (“winter worm, summer grass”). But for many people the most appropriate name would be zombie-creating fungi, because they can cause certain insects to act like zombies when they become infected by these fungi.

Cordyceps and Ophiocordyceps are members of the ascomycetes (sac fungi) and most species are endoparasites that mainly attack insects and other arthropods (scientific term for such organisms is entomopathogenic fungi). These fungi have a worldwide distribution with approximately 400 species in the genus Cordyceps alone. They are particularly abundant and most diverse in tropical rainforests and in humid temperate forests. One of the best-known species of this group of fungi grows in the body of ants and releases chemicals that cause the host ant to climb up vegetation and attach itself to a leaf or twig before the ant is killed by the parasite. (Mind control at its best; zombie ants following the instructions of a fungus growing inside of them.) The fungus then produces a spore-releasing stalk that grows out of the head of the victim and produces spores that can infect more ants on the ground below. Ants contacting spores while foraging become infected and the fungus quickly spreads throughout the body of these ants and the life cycle repeats itself. The following BBC video shows Cordyceps (Ophiocordyceps sinensis) parasitizing an ant:

A carpenter ant infected with a zombie ant fungus in the genus Ophiocordyceps. Once the fungus kills its hapless drone it grows a spore-releasing stalk from the ant’s head in order to infect more ants. Credit: Kim Fleming

Spores of the Cordyceps fungus germinate in the host insect producing a mycelium that eventually digests and replaces the host tissue. The fruiting body of the fungus is called an ascocarp and varies in shape but is often cylindrical or branched. The ascocarp bears small flask-shaped structures called perithecia in which are found the asci containing thread-like ascospores, the sexual spores of the fungus.

Cordyceps is from the Latin words cord, meaning “club”, and ceps, meaning “head.” Several members of this genus are considered to be of medicinal value and are found in pharmacopeias of traditional Chinese and Tibetan medicines. (See figure below of stroma from the Cordyceps fungus that are said to have medicinal value.) The fungus is said to increase energy and stimulate the immune system. Other claimed health benefits include: cholesterol reduction (red rice yeast is another fungus said to have this property), increased efficiency of the circulatory system, anti-tumor properties, liver protection from harmful toxins, and of course sexual potentiator. Cordyceps sinensis appears to assist in aiding better cell function and greater energy because it dilates the airways in the lungs, allowing more oxygen to reach the blood and thus tissues. Biochemical studies of Cordyceps and related fungi do indicate that they possess various chemicals that are believed to be effective in promoting some of the health benefits claimed by practitioners of traditional medicine.

An interesting side note to this story of the zombie fungus is that Ophiocordyceps, the genus that attacks ants, has a hyperparasite that feeds on the fungus which is feeding on the ants and prevents it from producing spores. (As Jonathan Swift would say, “So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ‘em, and so proceed ad infinitum.”) This lack of spore production thus reduces the destruction of ant colonies. See the following link to read more about this hyperparasite.