January's (2010) Mushroom is all about...
The bad boys of mycophagy*the genus Amanita
Amanita mushrooms are some of the most beautiful and elegant
mushrooms one can encounter. They have the classical mushroom
stature and appearance that has been immortalized in cartoons and
movies. Amanita muscaria represents the classic example of a
toadstool for many people. The term toadstool
typically refers to a poisonous or undesirable mushroom. Although
extremely well-known and beautiful, A. muscaria along with a
few of its close relatives are responsible for many poisonings. Some
cases prove to be eventually fatal, given the genus Amanita
top-priority for any would be mycophagists (people who eat
What makes Amanitas so notorious is the fact that there are a few edible look-alikes. The most common mistake would be thinking that a deadly Amanita such as a Death Cap (A. phalloides) or Destroying Angel (A. virosa and others) might be a Paddy Straw mushroom (Volvariella sp.) or puffball. All Amanitas develop from a round ball that resembles an egg. The mushroom matures inside this protective covering and eventually rips through the encasement allowing the mushroom to grow upright and eventually open its cap. This encasement, the universal veil, is what leaves remnants on various parts of the mature mushroom (scales or patches on the cap and a volva at the base of the stem). Agaricus mushrooms and Amanitas also develop gills under the protection of a partial veil which leaves remnants as it tears when the mushroom matures (a ring on the stem and sometimes fragments below the rim of the cap). The gills of Agaricus mushrooms start white, then rapidly go to pink and then finally dark brown. The dark color of the spores and different habitat, grasslands versus woods respectively, should make it easy to separate Agaricus from Amanita. The other possibility would be to confuse a young Amanita egg with a puffball. Cutting lengthwise anything resembling an egg before eating is highly recommended even if it truly is a puffball. The puffball will be all white inside whereas the Amanita egg will show a tiny mushroom shape inside. One old puffball with mature spores (brown or yellowish inside) can ruin any other foods mixed with it. All Amanita species will produce white to off-white spores. This, combined with the habitat and stature make it difficult to misidentify Amanitas.
Some people eat Amanitas rather indiscriminately in Asia. It is not uncommon to see bags of mixed Amanitas as well as other mushrooms (like white Russulas) being sold in markets during the rainy, summer months. Fortunately, the deadly varieties of Amanitas (A. virosa, A. bisporigera and A. phalloides) do not seem to grow in Southeast Asia. They do occur frequently in North America, which represents a problem for people who are not aware that some species are deadly poisonous. Complications occur when Asian immigrants pick and eat A. phalloides believing that they have found a Paddy Straw mushroom (Volvariella sp.), because they are unfamiliar with Amanitas. This mistake takes the lives of a few people every year. The Paddy Straw mushroom is a staple of Asian cuisine, so finding what would seem to be a free meal in the forest is welcomed. One of the obvious differences between an Amanita and a Paddy Straw mushroom is the habitat. As the name implies, Paddy Straw mushrooms like lignocellulolytic substrates for growth such as straw from rice paddies. Amanitas are mycorrhizal and grow in forests with their partner trees. Another obvious distinction between the two types is the spore print color. Paddy Straw mushrooms will give a pink spore print while Amanitas will produce a white to buff spore print.
Amanitin is one of the toxins present in the deadly Amanitas as well as a few other poisonous mushrooms. This toxin works by binding and therefore inhibiting the action of a very important enzyme call RNA polymerase II. This enzyme is responsible for turning the genetic code contained in our DNA into messengers that are carried throughout the body. Much of this activity takes place in the liver. When the poison is ingested it initially causes gastrointestinal distress (vomiting and diarrhea) from which the patient recovers. Eventually despite the GI distress, the toxin is absorbed by the patient’s body, making its way to the liver where it essentially stops our bodies from working. Because the effect is delayed for several hours or more, by the time serious illness symptoms are noticed, the poison has destroyed the body’s ability to recover, usually necessitating a liver transplant or other drastic measures to prevent death.
* Mycophagy is the practice of eating fungi; especially wild mushrooms.