July 31, 2008

Wachusett Wednesday: Eat and Be Eaten Edition

I spent most of my energy on looking for beetle-infested polypores during yesterday's visit to my field site at Wachusett Mountain. Nonetheless, I saw a number of interesting specimens among the prolific mycofauna and collected a few. This included a couple of very interesting and rarely collected fungi and one truly excellent edible. Two of the fungi presented here, Nyctalis agaricoides and Elaphocordyceps ophioglossoides, specialize in eating other fungi. Cannibal fungi and tasty Lactarius are automatically interesting things, but that would leave out an oddball Cortinarius species known only from Massachusetts that I also present here. The flies were interesting, too, but I mean that in a different way. A species of brown fly with white-banded wings kept the foray particularly exciting as they bit chunks out of exposed skin, undeterred by repeated application of DEET. Yes, it hurt. The collections made yesterday are almost worth it, though.

The genus Coltricia is collectively known in colloquial terms as the "fairy stools." They're stipitate-pileate members of the order Hymenochaetales. The majority of this order look more like polypores in general morphology and a number of them are resupinates (e.g., they form crust-like growths). This species, Coltricia cinnamomea, is unusual in being a hymenochaete that has a distinct cap-and-stem arrangement; it's probably an example of convergent evolution. The morphology has arisen independently several times in the Basidiomycetes. Despite the similarity of appearances, Coltricia are about as closely related to "true" polypores like Polyporus as humans are to shrews.
As far as I've been able to find, Cortinarius dionysae has been collected only in Massachusetts. The purple color you see in these photos fades very quickly once the mushroom is removed from the substrate, changing to a pale brownish color within a few minutes as the mushroom dries. The largest pileus was very nearly 10 cm in diameter and the stipe is quite robust as well, terminating in a large bulb at the base. The universal veil leaves a sheath on the lower stipe that has a free collar, reminiscent of those commonly found in Amanita. Unlike most purple corts, C. dionysae has almost no bitter taste. The spores are shaped like lemons, also a bit of a departure from most other members of the genus. The flesh inside this mushroom is mostly white, but strong purple streaks can also be seen, particularly in the cap and top of the stipe. The edibility of this mushroom isn't known, but many corts are poisonous and some of the purple ones can be particularly nasty. I wouldn't suggest being the one to find out; it probably wouldn't be lethal, but it could do some serious damage to the digestive system.
Elaphocordyceps ophioglossoides is one of the most interesting fungi in the world, and not just because its scientific name is such a mouthful. Most corcycepioid fungi are parasites on insects, killing them in rather spectacular and gruesome ways. Think Alien here. The spores infect a host, sometimes altering its behavior, and eventually the fruiting body emerges from the hapless arthropod's body. E. ophioglossoides, however, is one of a handful of these ascomycetes that have made the jump to some other host, in this case another fungus whose fruiting body is a false truffle in the genus Elaphomyces. Others parasites in the same genus haven't made that jump, though, and the closest relatives of the fungus you see in these photos are parasites of cicada nymphs. In an important sense, this host jumping is crystal clear evidence for an evolutionary mechanism called host-jumping. Researchers Naruo Nikoh and Takema Fukatsu published one of my favorite papers ever written about fungi on this very subject:
Nikoh N and T Fukatsu. 2000. Interkingdom Host Jumping Underground: Phylogenetic Analysis of Entomoparasitic Fungi of the Genus Cordyceps. Molecular Biology and Evolution 17:629-638
In the time intervening, and based partly upon their work, the genus Cordyceps has been split up quite a bit. Check out Joey Spatafora's exhaustive website on the group of fascinating fungi, An Electronic Monograph of Cordyceps and Related Fungi, for more about the current state of knowledge about these intriguing parasites.
It took me about an hour to figure out that this is Inocybe tahquamenonensis, a fungus that isn't at all rare but is seldom collected because it's small and nearly impossible to see against the forest floor. Unlike many members of its genus, this Inocybe is also odorless. Many of the Inocybes have odors variously described as crushed green corn, bleach or spermatic (which brings up some intersting questions of how mycologists might spend their free time that we won't get into here). Personally, I have a very poor sense of smell and in the past relied on former labling (and now associate professor at the University of Tennessee at Knoxville, though his faculty page isn't up yet) and Inocybe expert Brandon Matheny to help me out with collections of this genus. He can actually distinguish subtleties of these stinky mushroom's aromas. I can divide them only into "stinky" and "not quite so stinky" categories. Still, he's promised free beer at the MSA conference next month, so I'm sure he wouldn't mind my bringing along a bag or two full of these mushrooms for inspection by his far more educated nose.

Eating any Inocybe is a bad idea. Most of them are poisonous. Some also contain hallucinogens, but the other compounds present insure that you'll have a very bad trip.

Nyctalis agaricoides grows on dead Russula mushrooms; the slimy, mealy black corpse in these photos was probably Russula compacta as this collection was made from the area dominated by R. compacta that I was in two weeks ago and it is still largely overrun with that mushroom. There are only a few species of Nyctalis and they're a strange bunch. As you can see from these photos, they look like typical agaricoid fungi, but they're definitely not. In the second image, you can see that they lack either gills, pores or teeth. Where the gills should be there is instead a layer of translucent, very stiff gelatinous material that starts out white and turns a buff-brown color in older specimens. While it's technically a basidiomycete, N. agaricoides makes few or no basidia (I couldn't find any in the specimens I collected), and that's probably why it no longer bothers making a hymenium like most of its kin. When it want to reproduce, this mushroom simply clones itself. It walls off a hyphal tip and turns it into an asexual structure called a chlamydospore (here's a photo of the chlamydospores of this species), and these are produced not under the cap like in most basidiomycetes but on top< of the cap, which degenerates into a mass of beige fluff. The spores aren't forcibly discharged, either. They're dispersed by the wind and look for another dead Russula to germinate upon. Each of the offspring is an exact copy of the parent since no sexual recombination takes place. Other sexually-reproducing fungi can also form chlamydospores when circumstances force them to do so, but Nyctalis is unusual in having given up sexual reproduction in favor of parthenogenesis almost completely.

A word of warning if you should happen to find any of these and think about bringing them home. They smell bad. Awful. They give off a powerful odor that combines garlic and phenolic compounds that can become nauseating in short order when confined to a room. The spore masses atop the fruiting bodies are very easily aerosolized, too. I learned this yesterday when I opened my collection box and was greeted by a puff of spores that I promptly inhaled. I could not only smell the things, I could taste them. Sucking down a lungful of asexual spores from an organism that lives as a scavenger, and has some mechanism by which it prevents the corpses upon which it thrives from drying out as they normally would, is likely a very bad idea. While it's unlikely that I'll wake one morning to find these pale little ghouls protruding from my ribcage, I would strongly suggest to others who might want to work with Nyctalis to do so under a hood or while wearing a pollen mask. The spores from these specimens were globular and 13 microns in diameter; use appropriate air filtration.

I can't imagine anyone wanting to try eating something that grows on slimy mushroom corpses, but I can't imagine these critters would taste anything other than perfectly horrible. I have no idea as to whether they're poisonous. Despite their being fairly repulsive, I find them very interesting and would like to know more about how these things evolved. I'll likely sequence them and check into the literature to learn more.

Moving away now from fungus that might eat you, here's a fungus that's good to eat. This is Lactarius volemus, which I consider a choice edible. I've collected and eaten these before; the last time was in Florida in 2002. Because of color variation I wound up collecting several of these yesterday, so half went into the dehydrator for archiving and the other half came home with me and wound up in a marsala sauce. They were excellent, far better than I remembered them from the last time I tried them.

When any part of this mushroom is nicked, copious watery white latex will ooze out. This doesn't change color after more than ten minutes, but it will stain the flesh a light brown and the gills a darker brown. The odor can be fishy, but it isn't always. While authorities always mention the fishy scent, in my experience that may be a product of some small amount of decay. In any case, it's older specimens that take on the odor. Younger ones are close to odorless and as a rule of thumb mushrooms taste better before they get old. The cap color varies from an orange-brown in younger specimens to the pumpkin orange you see here in mature ones. The stipe is concolorous with the cap or a bit lighter and often fades to white at the apex. The gills are a pale cream-yellow color, often with brown bruises. The whole mushroom is finely pubescent; using a magnifying glass while make that feature more readily apparent. The spores are generally globose; the ones from the specimens I found yesterday were about 8 microns in diameter. Taste-testing the uncooked mushroom resulted in no acrid flavor at all. Cooking it in marsala wine and spooning it over pork chops resulted in a deeply appreciated deliciousness that almost made up for the bits of skin I'm now missing from the back of my head due to the nasty Diptera that think we humans far tastier than any Lactarius could ever hope to be.

From the "There's a reason that they call it a variable Russula" department:

Look at the mushroom in the photos to the left. Take a good, long look, noting coloration and morphology. Now take a look at this Russula, collected two weeks ago. They don't look at all alike, do they? According to current systematics, though, these are the same species, Russula variata. It's hard to believe (in fact, I'm not sure I believe it myself), but aside from the gross morphology, these two very different-looking fungi share all of the same traits. The repeatedly-forking gills, the lack of any color change in FeSO4, the size and shape of the spores and the presence of an amyloid reticulum joining the <0.5 micron-high warts on them... there's little doubt that this is also R. variata.

I wonder, though, whether this is more a matter of convenience than a true phylogenetic hypothesis. Despite the taxonomic peculiarity, I have a hunch that what's called R. variata is actually a few species lumped together. Maybe mycologists are spending too much time thinking about spermatic Inocybes and Amanita with constricted volvae!

Flies eat people. People eat wild mushrooms that probably contain a few fly larvae. Fungi eating other fungi. Fungi eating insects. It's an eat-or-be-eaten world out there. Or more properly, it's eat-and-be-eaten.

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