#051: The Death Cap, Amanita phalloides
NEVER EAT AN AMANITA. Please keep reading if you don’t know what that sentence means. Amanita phalloides is perhaps the leading cause of deaths due to mushroom poisoning in the United States. The danger with the Death Cap is that it is often mistaken for an edible look-alike. Avoiding the Death Cap is not difficult once you learn to identify Amanita Although some Amanitas are edible, it is much safer to pass up every mushroom in that genus. The following list will help you identify A. phalloides:
- CENTRAL STIPE: The stipe (or stalk that lifts the toadstool’s cap above the ground) is always connected to the center of the cap. The texture of the stipe may be smooth or finely hairy. The bottom of the stipe is usually expanded so that the base of the mushroom is bulb-like. Sometimes the base is found just below the ground, so always make sure to dig up the entire base when identifying a mushroom. The Death Cap is mycorrhizal (mutualistic) with the roots of nearby trees, so it is always found growing on the ground.
- FREE GILLS: The gills on the underside of the cap usually do not touch the stipe. Sometimes, however, the gills are found just barely touching the stipe.
- SKIRT-LIKE RING: The gills are covered by a thick membrane called the partial veil while they are still developing. Once mature, this membrane separates from the cap but remains connected to the stipe. In mushrooms that are fully opened, this membrane persists as a ring hanging from the stipe a little bit below the cap. The ring is thick and ends up looking somewhat like a skirt.
- SAC-LIKE VOLVA: When the mushrooms are very young, the entire fruiting body is surrounded by another membrane called the universal veil. As the cap grows and expands, it breaks through this membrane and leaves behind two types of membrane fragments. The first type is called the volva and it is found around the base of the mushroom. The volva looks somewhat like a small sac in which the toadstool’s stalk rests. Imagine a clip art picture of a newly hatched chick. The volva is equivalent to the bottom piece of the shell in which the baby bird is still standing. The universal veil can also leave pieces of tissue called warts and patches on the top of the cap. This is equivalent to the bits of eggshell dotting the clip art chick’s head. Like the eggshell pieces, warts and patches are not attached to the mushroom and can be easily brushed off. Death Caps usually have bald caps, but are sometimes found with large patches of the universal veil resting on the top of the cap.
- WHITE SPORE PRINT: Perhaps the best way of separating out Death Caps from their look-alikes (especially for the novice mushroom hunter) is by examining the spore print color. To take a spore print, cut off the cap of your fresh mushroom and place it gills-down on a piece of paper (blue paper works best). In a few hours, you should have a layer of spores on the paper underneath the cap. A. phalloides, along with all other Amanita species, has a white spore print. Sometimes you can guess a mushroom’s spore print color by looking at the color of its gills. The gills of the Death Cap are white, as with other Amanita species. However, gill color often varies with age and should not be used in lieu of the spore print. Death Caps are often confused with the Paddy-Straw Mushroom (Volvariella volvacea), which has a pink spore print.
- CAP COLOR: I have listed cap color last because it is highly variable in the Death Cap. The toadstools are typically yellow to yellow-green. However, they can also produce mushrooms that are green, brown, white, or various combinations of those colors. The cap is also characterized by a multitude of tiny, fiber-like streaks of darker color that radiate from the cap’s center. The stipe is white or colored a paler version of the cap’s color.
If you read last week’s post, this list should sound very familiar. Both the Death Cap and the Destroying Angels are found in the genus Amanita and therefore share many characteristics. The general factors in points 1 through 5 in the list above are common to almost all Amanitas. You should never eat a mushroom with those characteristics because many are deadly poisonous. Make sure to go through this list for every toadstool you collect for the table. Multiple species of mushrooms are frequently found fruiting side by side, so you must check every one. Remember: when in doubt, throw it out!
One of the more interesting things about A. phalloides is that it is an invasive species in North America. The Death Cap is placed in phylum Basidiomycota, class Agaricomycetes, order Agaricales, family Amanitaceae, genus Amanita and subgenus Lepidella. This toadstool has close relatives that are found in North America, but it is actually native to Europe. It was most likely introduced to this continent with ornamental trees (especially Cork Oak) imported from Europe. The first introduction of the Death Cap was probably to California around 1938. Since then, A. phalloides has colonized native trees and can now be found throughout California. The Death Cap has apparently also been introduced to New Jersey and New York, although its eastern range (Virginia to Maine) is not yet as extensive as its western range. This mushroom’s preferred hosts are oaks of various species and pines. In California, the Death Cap has only recently begun growing under pines. A. phalloides is unusual among non-native mushrooms. Most other introduced species are decomposers and stick to unnatural habitats, like mulch. This enterprising, mycorrhizal toadstool, however, has managed to colonize a wide variety of native trees and is truly an invasive species. So what has made A. phalloides so successful? In short, nobody knows. One theory is that the Death Cap is “cheating” the mycorrhizal relationship by taking more resources from the host tree than it is giving back, but this has proven impossible to test. Some mycologists have also worried that A. phalloides is “crowding out native species”, but this, too, is impossible to verify.
The Death Cap, like the Destroying Angels, is deadly poisonous because it contains amatoxins. These small cyclopeptides (proteins with their amino acids linked to form a closed circle) inhibit RNA Polymerase II, which transcribes DNA into mRNA. This is a crucial step in protein synthesis, so cells containing amatoxins are prevented from making new proteins and will eventually die. The first symptoms of amatoxin poisoning are similar to food poisoning and are not experienced until 5 to 24 hours after ingestion. This DELAYED ONSET OF SYMPTOMS mistakenly convinces some people that the mushrooms they ate are not related to their current distress. The symptoms ameliorate after a while, so many people decide not to go to the hospital. By the time the symptoms return, the liver and kidneys are often damaged beyond repair. At this point, liver transplant is required for the patient to survive. If amatoxin poisoning is diagnosed quickly, there are a few other treatments available. One is the administration of silibinin intravenously, which prevents the uptake of amatoxins by the liver. Another is the administration of high doses of penicillin, which helps stimulate the liver’s defences. Immigrants from Southeast Asia make up a large percentage of the people who die from eating the Death Cap. They are familiar with the Paddy-Straw Mushroom, but not the Death Cap because the latter is not found in Southeast Asia. The important point hiding in this information is that mushroom hunters are only experts in their own region. Never eat any mushrooms you find in an unfamiliar part of the world. The group with the absolute highest number of deaths from A. phalloides is the canine population. You can protect your dog’s health by looking out for deadly mushrooms such as the Death Cap.