LSM1303 Animal Behaviour Student Blog : Cordyceps

Inhuman Doctors: Zoopharmacognosy and Self Medicating Animals

Vigneshwaran Shunmugam — Fri, 21 Mar 2008 15:15:00 GMT

Many major cultures around the globe have developed some form of medical science. The Indians have Ayurveda, the Chinese have TCM and of course there is Western medicine. What these fields have in common is that they are derived from the process of observing the effects of certain herbs or foods on the health of the imbiber and thus correlating cause and effect. While medical science and its practitioners have long been held to be at the forefront of human intellectual pursuits, we now realise that this was no great achievement at all. In fact, even monkeys do it.

Observe this Orang Utan for example.

Right. This is just a monkey opening a packet of powder. Nothing fancy. However, monkeys DO develop their own medical techniques to deal with their own health issues. This is known as Zoopharmacognosy which is basically the animal form of Medical Science. Many species of animals use various techniques to deal with their maladies.

If you have seen your dog or cat eating grass you may have been puzzled at their sudden vegetarianism. They do have good reason for doing so. Eating grass "stimulates either retching or the rapid expulsion of worms in diarrhea" (Hart and Hart 1985). Compare this with the Tamil proverb which claims that a Tiger would not eat grass, no matter how hungry.

Medicine is not a purely mammalian pursuit either.Snakes too have herbological knowledge! "According to Chinese folklore, many centuries ago a farmer in the Yunnan district found a snake near his hut. Fearful for his life, he beat it senseless with a hoe and left it for dead. A few days later, the same snake returned. Again he tried to kill it, but again it returned. After he had beaten it a third time, the farmer followed the severely wounded snake as it crawled into a clump of weeds, started feeding on them, and thereby rapidly cured the worst of its injuries. The plant in the story was Panex notoginseng, which now forms the main ingredient in the herbal formulation 'Yunnan bai yao', a white powder that cauterizes cuts and stems external bleeding immediately. It was standard issue in the Vietnam War, for use when soldiers were wounded far from conventional medical treatment. "(Reid 1987).

Our closest cousins, the Great Apes have various methods by which they keep themselves in the pink of health.

Above we see a chimpanzee(Pan troglodytes) chewing on the bitter pith of the Vernonia Amygdalina plant. Chewing on the pith allows the chimp to extract the bitter juice that is within. THe chimpanzees use this method to kill parasites in their intestinal tracts. Interestingly, chimps do not usually eat this leaf due to it being slightly toxic to them. Thus, they only eat this leaf for medicinal purposes! This paper has extensive information on this phenomenon, complete with graphs. The author Michael Huffman is an eminent figure in the field of Zoopharmacognosy.

Chimps sometimes consume the leaves of the Aspilia plant, which they got to great lengths to obtain. The leaves are covered in stiff hairs and are swallowed whole, despite the difficulty of doing so. "Huffman doesn't doubt that there is a medicative function behind leaf swallowing behavior. His theory about how it gets rid of worms revolves around the hairiness of the leaves. Huffman found live worms in chimp *** stuck "like Velcro" to leaf hairs and trapped within the folds. He speculates that worms may become attached to the leaves or somehow enticed into the folds during digestion, taking a "magic carpet ride" through the gastrointestinal tract, eventually to be excreted from the body. Chemicals in the plant may also decrease the ability of the parasites to adhere to the intestine, making it easier for them to be swept out by the leaves."

Perhaps the animal use of medicines to treat themselves is not such a surprising phenomenon. In fact post-Darwinists should have predicted it regardless of evidence. Using medical methods enables an animal to prevent its death,prolong its life, to heal faster and have a survival advantage. This is an advantage that would allow those animals who use it to be more successful than those who dont. In the abscence of a consequent negative selection pressure, animals who self-medicate would definitely outsurvive those who do not. Thus, Zoopharmacognosy is not surprisingly prevalent in the animal kingdom.

Not only do animals consume herbs and plants as medicines, but they also consume certain types of soil(geophagy) and insects for the same purpose.

Even more interesting than the fact that animals employ medical science is the fact that many of the herbs and techniques employed by animals are similarly employed by humans. This highlights the cross pollination of medical knowledge from the animal kingdom to ours.

To learn more on the exciting field of Zoopharmacognosy, this book might help.

"Really Wild Remedies—Medicinal Plant Use by Animals" by Jennifer A. Biser. Zoogoer, January/February 1998

Huffman, M.A. 2001. Self-Medicative Behavior in the African Great Apes: An Evolutionary Perspective into the Origins of Human Traditional Medicine. Bioscience, 51(8):651-661.

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Possessed ants and other animals - What has gotten into them?

Chen Shang Teng Evelyn — Tue, 18 Mar 2008 16:36:00 GMT

What do you make of ants that climb to the top of leaves and stay there, or grip onto the tip of leaves with their mandibles and hang there until they die? These are behaviours atypical of them - are they possessed? Have they gone mad? Take a look at the following video for an explanation:

In the video, spores from a parasitic fungus from the genus Cordyceps enter a bullet ant, infecting its body and its mind. The spores enter through the ant's spiracles, which are holes in its exoskeleton that allows it to breathe. The spores then attach on to the ant's soft tissues (though avoiding its vital organs) and start to grow.

Once it reaches sexual maturity, it is time for the fungus to sporulate. This is when the ant is directed to climb upwards and grip onto the plant with its mandibles.
How is this so? At this point, the fungus starts growing into the ant's brain, and produces chemicals which alters the way in which the ant perceives pheremones. The fungus then manipulates the ant to perform such a behaviour.
Why the specific behaviour of climbing upwards? Well, the parasite directs the ant to climb upwards so that when the fungus disperses its spores, the airborne spores can land on a bigger area and potentially affect more insect hosts. Thus, when the ant is high up off the ground, the fungus then consumes the ant's brain and, like out of a science fiction movie, shoots out of its head and grows for 3 weeks before exploding and spreading its airborne spores over the area. And the cycle repeats.

One interesting snippet of information from the video is how the other bullet ants from the colony were able detect the infected ant and also recognised the danger it posed to them, moving the infected ant as far away from the colony as possible. Some questions that comes to mind: How are they able to detect the infection? Is it a learnt or an instinctive behaviour? After millions of years of co-evolution between the ants and the fungus, ants have learnt that to survive, they had to be able to smell and also chemically detect the parasitic fungi infection. They would then immediately take action to prevent the infestation of their whole colony. To do this, they have in place a sentry system, where soldiers guard the queen and her brood by preventing entry to enemies, included infected ants. When these ants are detected, they are quickly killed and taken far away from the nest.

Another interesting bit was on how there are thousands of different species of Cordyceps fungi, and each targets a specific, unique insect host. The series of images shown in the video on this was, for me, oddly beautiful. It seemed as if different varieties of colourful fungi were growing out of strange yet creative flowerpots that only Mother Nature could have provided. This also goes back to the previous point where co-evolution has also resulted in the need for fungus to recognise its specific insect host through biochemical signals.

"In general, members of Cordyceps show stricthost specificity, although the degree of specificity differsfrom species to species. Some parasitize only a single hostspecies (e.g., Cordyceps sobolifera, strictly on the nymph ofPlatypleura kaempferi in Japan), while others utilize a rangeof hosts from a particular taxonomic group (e.g., Cordycepsmilitaris, on the pupa of various moths) (Shimizu 1994 ). Themajority of Cordyceps species utilize insect hosts from variousorders such as Homoptera, Lepidoptera, Coleoptera, Hymenoptera,and Diptera, suggesting that major host shifts between insectorders have occurred in the genus." (Interkingdom Host Jumping Underground: Phylogenetic Analysis of Entomoparasitic Fungi of the Genus Cordyceps, Molecular Biology and Evolution, 2000)

In the video, the main fungus shown was the Cordyceps unilateralis, which specifically targets ants.

(Image taken from http://www.utexas.edu/courses/zoo384l/sirena/species/fungi/)

This is a fly with the parasitic fungus, Cordyceps dipterigena.

(Image taken from http://www.utexas.edu/courses/zoo384l/sirena/species/fungi/)

And of course, if you haven't realised by now, the cordyceps used in Traditional Chinese Medicine (TCM), is also from the Cordeceps genus. The most commonly used species is Cordyceps sinensis, and is also known as terms such as caterpillar fungus and vegetable caterpillar. And, (gasp!) as you might have guessed, this species is not unlike its relative shown in the video except that rather than parasitise ants, it parasitises caterpillars! More specifically, the larvae of particular types of moths such as the bat moth, Hepialus armoricanus. The larvae is said to ingest or inhale the spores of the fungus. During the pupa stage underground, the fungus then dissolves the internal organs of the pupa, and fills up the hollow shell before bursting through the pupa and above ground to disperse its spores. Cordyceps is said to be effective in treating kidney and lung problems, and is a very popular choice of chinese medicine used.

(Image taken from http://taos-telecommunity.org/epow/EPOW-Archive/archive_2003/EPOW-030428.htm)

If you are interested in other parasite-host relationships, you can go to the following links:
Snails infected by parasitic worms, causing tentacles to look like prey for birds [video]
Black wasps lays eggs in aphids [video]
Ants infected by liver fluke worms display abnormal behaviour [video]
Suicidal grasshoppers [article]
Ants neglect own brood to take care of caterpillars [article]
Parasite make ants resemble berries [article]

As can be seen from above, most of the time, parasites manipulate their hosts' behaviour to benefit themselves. In the example of the bullet ant, the cordyceps fungus manipulated the ant's mind and made it climb upwards onto a plant, so that its spores can be dispersed onto a wider area. However, in this article, instead of feeding on more types of plants to provide a supply of live tissue for the parasites as food, the caterpillars that got infected started eating only plants that were toxic to the parasites. Why exactly does this happen is still not known to scientists, but this gives us a fresh insight on the parasite-host relationship where in this case, the host wins the battle for once.

Therefore, possessed ants and other animals - what has gotten into them? Now you can answer that question - parasites.

References:

Elsewhere in Nature. Emerging Infectious Diseases, 8(9), 2002.
Pontoppidan, M. B.; Himaman, W.; Hywel-Jones, N. L.; Boomsma, J. J.; Hughes, D. P.; 2007. Genetic population structure in Cordyceps - fungi parasitizing Camponotus ants. International Meeting on "Population and Evolutionary Biology of Fungal Symbionts", Ascona, Switzerland.
"Brainwashed by a parasite." 20 Nov, 2006.
"Your Monday Morning Parasite Show (Safe for Breakfast)," by Carl Zimmer. 4 Dec, 2006.
Nikoh, N.; Fukatsu, T., 2000. Interkingdom Host Jumping Underground: Phylogenetic Analysis of Entomoparasitic Fungi of the Genus Cordyceps. Molecular Biology and Evolution, 17:629-638.
Halpern, G.M., 2007. Healing Mushrooms, Square One Publishers, Inc.
"EPOW: Ecology Picture of the Week," by Dr. Bruce G. Margot. 28 Apr - 3 Mar, 2003.
Relph, D., 1991. Caterpillar-killer. New Zealand Geographic, (Oct-Dec): 114-119.
Fuchs, N. K., 2006. The Health Detective's 456 Most Powerful Healing Secrets, Basic Health Publications, Inc.
"Fungal Parasites of Ants," by Don Glover. Sydney Fungal Studies Group, Inc.
Stamets, P., 2005. Mycelium Running: How Mushrooms Can Help Save the World, Ten Speed Press.
"Fungi of Sirena," by L. E. Gilbert. Graduate Field Course in Rainforest Research, 2003.
"Cordyceps Fungus," posted 3 May, 2007.
"Zombie Snails," posted 6 Mar, 2006.
"Parasitic Wasps and Aphids," posted 27 Feb, 2008.
"Parasitic Mind Control," National Geographic Video.
"Suicide Grasshoppers Brainwashed by Parasitic Worms," by James Owen. National Geographic News, 1 Sep 2005.
"Parasite Makes Ants Resemble Berries," by John Roach. National Geographic News, 16 Jan 2008.
"Caterpillars con ants with smell." BBC News, 4 Jan 2008.
"Grubs fight parasites with food." BBC News, 1 Aug 2005.