Amanita marmorata subspecies myrtacearum, a Hawaiian mushroom in honor of Dr. Orson K. Miller, Jr.

Tom Volk's Fungus of the Month for August 2007

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In mid August the North American Mycological Association is holding the Orson K. Miller, Jr. NAMA foray in Pipestem, West Virginia. This amazing group of largely amateur mycologists holds a foray each year in an interesting locality, where members from all over meet to collect mushrooms and argue about what to call them. Occasionally the foray is named in honor of a distinguished mycologist, and for me there was no one more distinguished than Orson. An eminent professional mycologist from Virginia Tech, he is revered by amateur and professional mushroomers everywhere. In honor of this month's 2007 Orson K. Miller, Jr. NAMA foray in Pipestem, West Virginia, I am delighted to have this month's fungus be Amanita marmorata subspecies myrtacearum, a mushroom Orson described from Hawaii with Don Hemmes and George Wong.

I actually saw this mushroom live when the Mycological Society of America (MSA) held its annual meeting on the big island of Hawaii in 2005. Besides all the formal meetings, with talks and poster sessions, the MSA always holds a foray before the meeting, just to get us back to our roots... er... hyphae. Besides walking in the woods and collecting fungi, we get to see lots of old friends and make some new ones. The top photo of this page was taken at the MSA foray in Hawaii, when someone found this fungus Amanita marmorata subspecies myrtacearum. Since Orson had described this mushroom with Don Hemmes and George Wong (1996), he was excited to see it and, consummate teacher that he was, started explaining the mushroom to the person who showed it to him. In just a few minutes an amazing crowd of mycologists gathered around Orson to hear him talk about his mushroom, completely encircling him like an annulus. You can see all the cameras clicking, and you can also see Hope Miller, Orson's wife and an excellent mycologist in her own right, in the background to the right in blue shorts. All these 150 or so people listened to Orson talk for about 10 minutes, which was pretty amazing considering that lunch and the lava cliffs of the ocean beckoned.

We got to see the mushrooms up close, and we saw that our mushroom looked much like its relative Amanita bisporigera except for the fibers on the top of the cap. The Hawaiian species also tends to get more gray as it ages. In addition, A. marmorata subsp. myrtacearum is much smaller, with the cap diameter of about 4-5.5 cm (1.5-2 inches), with a stalk only 4-8 cm tall (1.5- 3 inches) and 0.5-1 cm wide (1/4-1/2 inch). Definitely not a tropical giant.

Both of these, along with Amanita phalloides belong in the subgenus Lepidella section Phalloideae. All of the members of the section Phalloideae have amyloid basidiospores. This means that they turn a blue-black color in Melzer's reagent, the components of which are iodine and chloral hydrate. Remember those experiments in school when you put a drop of iodine on a piece of paper-- and it turned blue? That was because of the cellulose in the paper. The same sorts of compounds are found on the walls of the basidiospores, accounting for the blue-black color. All the members of the Phalloideae (and most other Amanita species) have both a universal veil and a partial veil (see this page on Amanita caesarea for labeled parts-- but note that A. caesarea is not in the Phalloideae. The universal veil covers and protects the whole mushroom as it is developing from only a few cells. When the mushroom sucks in water, it expands greatly and breaks the universal veil, leaving a cup at the base called a volva. The annulus (ring) on the stalk is the remnant of the partial veil, which protects the gills while they are developing.

Amanita marmorata subsp myrtacearum is, as the name would suggest, a subspecies of Amanita marmorata, which is found in Australia. The subspecies myrtacearum has been found on six Hawaiian islands fruiting in association with non-native Eucalyptus and Casuarina species. Miller et al. hypothesized that the species may have made it to Hawaii on trees brought from Australia many years ago. It is unclear whether the introduction of the species happened more than once-- this would make an excellent population genetics study for someone. The original species has apparently changed enough that it can be considered a different subspecies. In the original paper, Miller et al. showed drawings of microscopic features that were clearly different, yet not different enough that they could be considered separate species.

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In the Miller et al. paper, they hypothesized that, like other members of the Phalloideae, Amanita marmorata would be expected to contain α-amanitin. This conjecture has been recently confirmed in a paper by Hallen et al. (2002). The toxin in the death angel mushrooms is a relatively small protein of eight amino acids, a cyclopeptide called α-amanitin . According to Dr. John W. Rippon, Professor Emeritus at the University of Chicago in Medical Mycology, α-amanitin works by slowly attacking RNA polymerase, an enzyme in the liver. It ultimately affects the central nervous system and kidneys. Unlike many fungal toxins it does not cause symptoms right away. 6-24 hours after ingestion there may be an early feeling of unease, followed by violent cramps and diarrhea. On the third day, there is a remission of symptoms, but this is a false remission. On the 4th to 5th day the enzymes increase and liver and kidneys are severely affected. Death often follows if a liver transplant or other heroic measures are not performed. The same toxin is, coincidentally, found in a completely unrelated mushroom Galerina autumnalis. According to some people who have eaten these poisonous amanitas (and later died), they have a rather good taste, so you can't trust your taste buds in distinguishing poisonous from edible mushrooms. However, I do not recommend tasting it!!!!! If you plan on eating any mushroom you must be absolutely sure of the genus and species identification. A meal, no matter how delicious, is not worth the price of your life.

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I hope you enjoyed learning about Amanita marmorata subsp. myrtacearum. It's an interesting fungus. I hope you can get to Hawaii to see it. To the right you can see me with Orson at the NAMA foray in Diamond Lake, Oregon in 2002. I always had a special fondness for Orson. I learned to key out mushrooms in his "Mushrooms of North America" field guide when I took Mycology from Jim Cavender at Ohio University in 1978. I think I probably met Orson for the first time at a NAMA foray (maybe in 1989 in Illinois? or 1990 in British Columbia? I don't really remember exactly). He and his wife Hope were always very nice to me and very supportive of whatever I was doing. Thanks for your friendship. Orson, we miss you.

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References

Miller, Orson K. Jr., Don E. Hemmes, and George Wong. 1988. Amanita marmorata subsp. myrtacearum, a new subspecies in Amanita section Phalloideae from Hawaii. Mycologia 88:140-145.

Hallen HE, GC Adams, A Eicker. 2002. Amatoxins and phallotoxins in indigenous and introduced South African Amanita species. South African Journal of Botany 68: 322-326. See http://www.msu.edu/user/hallenhe/Research.html for a pdf file.

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