July 17, 2008

Wachusett Wednesday: Russula Riot

My collecting trip to Wachusett Mountain yesterday netted a couple of very promising polypores that are riddled with beetle galleries. I'll be dissecting those in the lab today, but I'm fairly certain that I caught a glimpse of a Diaperis sp. at the entrance to one gallery when I picked up the specimen. It will be interesting as always to see what's living in the old fruiting body.

My field site is now practically sheathed in Russula spp. now. They're not the only mushrooms I saw, of course, but their fruiting bodies now dominate the south slope. Three species in particular are most prevalent (images below), led by the ubiquitous Russula emetica. With the fruiting of the russulas comes the germination of Monotropa, the Indian pipe. These ghostly white plants have given up photosynthesis in favor of a relationship with Russulales that reverses the typical relationship between plants and fungi. Russulas are mycorrhizal with various trees; that is, they form a hyphal network with the tree roots and receive plant-manufactured sugars in exchange for providing minerals that they gather from the soil, particularly phosphorous and nitrogen compounds. Monotropa roots also network with russula hyphae, but the plants leeches the photosynthate sugars from the fungus and provides nothing in return. Monotropa is thus a parasite on not only the russulas but, indirectly, upon the trees themselves through the mediary of the mycorrhizal associate. When the russulas prosper, so does the Monotropa. The relationship is called mycoheterotrophism; Tom Volk wrote a piece about it featuring Monotropa a few years ago which you can read here.

Here's a sampling of the more interesting stuff I found at the field site yesterday, including some of the Russula and Lactarius spp.:

One of the dominant Russula spp. in the higher elevations of the south slope is this grass-green version of Russula variata, the variable russula. This can be a maddening species to identify; coloration of the pellicle (the skin that covers the cap) varies all over the map, and the species seems capable of hybridizing with other russulas to produce a bewildering diversity of morphologies in many regards. When I saw this in the field, I thought it was Russula heterophylla, which I'd collected on July 4 at a much lower elevation. It wasn't until I'd tested my specimens with a bit of 10% FeSO4 solution that I realized it wasn't the same fungus at all. R. heterophylla quickly turns salmon-pink in FeSO4, whereas R. variata doesn't react at all. The other big difference is in the structure of the lamellae, and this is the character that can most quickly distinguish R. variata from the numerous other russulas it may resemble. Many russulas have gills that fork close to the stipe, but R. variata lamella almost always fork repeatedly, not only at the stipe but also at quite some distance from it. R. heterophylla pellicles are also totally green, though they may contain various shades. R. variata rarely has such a uniform coloration and will typically contain some brown, white, and/or buff tones as well. It's reportedly edible; I haven't tried it and considering its ability to hybridize I probably won't try any from Wachusett because while these green mushrooms were extremely common yesterday, they were often growing in close proximity to R. emetica, the mushroom that truly dominated the higher elevations. I would imagine that an emetica/variata hybrid might not be a good thing to eat.
At lower elevations, the dominant russula right now is Russula compacta, the hard russula. This species is also somewhat variable in color but is generally somewhere in the neighborhood of biscuit brown pellicle pigmentation. It's also edible, and while I haven't tried it myself I do have a few extra specimens in a bag in the fridge and intend to do so tonight. Fully mature specimens often have cracked to areolate pilei as shown in this photo. The lamellae in this species are generally white though they may turn ochre in age and they'll bruise brown when handled in any case. The flesh in the cap turns gray in 10% FeSO4, too. This is another species with gills that fork at the stipe and numerous lance-shaped cystidia. The pileal margin of this species also frequently remains inrolled in mature specimens in my experience as well, lending another character that helps to distinguish R. compacta from numerous look-alikes.

Note that the cracking on the pileus of this specimen clearly forms a cross. Maybe I should tag this as a Daily Jesus entry as well?
A detail shot showing the stipe and lamellae of Russula compacta.
The false coral, Tremellodendron pallidum, is another species that I collected earlier at a lower-elevation site elsewhere (about 150m vs 365m this time). This specimen is much more mature than that one, though. The branch tips have become darkened with spores and the fruiting body is generally larger with more and longer branches. I found numerous specimens of T. pallidum growing in wet places under both hardwoods and Tsuga; this seems to be the peak season for this organism on Wachusett Mountain. Most coral fungi aren't edible, and some are deadly poisonous, but since T. pallidum isn't a true coral fungus that doesn't apply; it's edible, though said not to be worth eating.
Another specimen of Russula variata found at slightly higher elevation. I'm including this image to demonstrate that even when R. variata is green, the shades of green can vary widely. This ponderous specimen (the cap is 15cm across and the stipe 8cm x 3cm) was lime green instead of grass-green, also with some brown tones on the pellicle. If you look carefully at the center of this detail shot of the lamellae, you might be able to see what I mean about the repeated forking. This specimen is large enough to actually see how far from the stipe some of the lamellae divide. I can't think of any other species under Russula have this arrangement. When in doubt about an identification in this genus, go right to the gills to rule out or include R. variata.
I'm calling this Sarcodon underwoodii for the moment, though there's also a chance that it may be S. imbricatus. While I suspect the former, it's too close to the latter to be definitive and I'll have to sequence it and compare it against both known sequences and that of my previous and more definitive specimen. The scales on this little cluster are much darker than on that specimen, so I'm not as certain. The second image is an extreme close-up of this Sarcodon's fertile surface. Again, the tiny teeth on these specimens are slightly under 1mm long by 0.35-0.4mm wide. If this does turn out to be S. underwoodii, I'll be letting the good people who run Wachusett Reserve know about it immediately. I don't think it's on any endangered species lists, but it is a relatively rare organism and something I'd think they'd want to know about once I've identified it definitively. My agreement with the state DCR stipulates that I provide the department with data periodically anyhow and while they haven't yet requested it from me, this would probably be a good thing to tell them about if it is, indeed, the rare S. underwoodii and not the more common S. imbricatus (for which sequences have been deposited in GenBank; molecular analysis is a wonderful thing!)
Lactarius corrugis is just beginning to come into its own, appearing in isolated groups. Like most of the specimens I saw yesterday, this little troupe has not yet fully expended their pilei and so have not yet taken on the corrugated texture from which this fungus derives its name. You can see in the second image the yellow, crowded lamellae that help to distinguish this species from the somewhat similar L. hygrophoroides; while both are edible, L. hygrophoroides is reputedly better than L. corrugis by orders of magnitude. You can also see the milk white latex that bleeds from the fungus when it is injured; in the case of L. corrugis, the latex gradually stains the flesh and lamellae a medium brown color over the course of about 15 minutes. Under the microscope, the cystidia of this fungus are so numerous that the appearance of the lamella tissue is like a wall of spears, each of which is up to 90 microns long by 9 microns wide and septate with walls up to 2 microns thick. If cystidia really are in part defensive structures, this is a mushroom that is practically screaming "Don't eat me!" It might be worth noting that while many of the less-defended Russula species I encountered yesterday were being consumed by slugs (but never beetles, interestingly), all of the L. corrugis specimens I found appeared to be completely unmolested. Even gastropods have their limits, I suppose. I, on the other hand, tasted some of this in the course of identifying it and found it to have a pleasantly smoky-sweet flavor that made me want to consume my specimens raw. A labling who also tasted it, however, found the flavor both acrid and resinous and was compelled to spit the stuff out immediately. It just goes to show how differently we humans can interpret stimuli, I suppose.
If sheer numbers of fruiting bodies are any indication of fitness in the case of fungi, then Russula emetica is literally king of the mountain right now. I'm not exaggerating in the slightest when I say that I saw hundreds of these yesterday. They're quite robust and are found at all elevations, though they are truly dominant in the landscape above 400m and give way to R. compacta below that altitude. It's possible that R. emetica is one of the most evolutionarily successful fungi in North America and perhaps one of the most successful of all organisms. I have collected it now from California to Massachusetts to Florida and have seen it in my travels between all three of those states. Wherever I've see hardwoods, I've seen R. emetica or Russula spp. so close to it that I suspect quite a bit of hybridization may occur. This is also the most toxic of the russulas; the strongly red-and-white coloration almost seems like a warning. It won't kill you, but anyone who swallows a bit of this stuff may soon wish they were dead as the fiery-hot toxins turns their digestive track inside-out and they begin vomiting up things that their great-grandparents had for breakfast. Still, because I am a cruel bastard, those who accompany me to the field who don't know this fungus are often put through a bit of a hazing whereby I give them a little piece and instruct them to chew it lightly for a few seconds and then spit. It usually takes about 30 seconds for the slight tingling they then feel on their tongues to turn into the full-blown burning sensation that R. emetica produces. That will fade in a minute or two, but in healthy specimens like that shown in this photo it's enough to literally bring tears to a grown man's eyes in the meanwhile. One odd fact is that rodents don't seem to be affected by the toxicity at all; I've watched squirrels, rats and chipmunks eat these mushrooms and then chased them off and sampled unmolested specimens from the same troop and, sure enough, my mouth caught fire like it always does.
Like the Sarcodon spp. to which it is distantly related, this Phellodon confluens is also a toothed ("hydnoid") basidiocarp. It's not exactly the most attractive of fungi, but it has a surprisingly attractive spicy odor and is perfectly edible though likely to be overlooked. This specimen was collected from the bank of a brook in a low-lying area dominated by maple and hemlock. It derives its specific epithet from its growth habit; what you're looking at in these images is not a single mushroom but numerous individuals that have fused together into a lumpy, rubbery, irregular mass. The spores in these species are very small (4 microns by 3 microns) and covered by spiky projections ("echidnate"). I've probably passed this stuff by many times in the past, but this time I had thought it might be some sort of polypore and so worth investigating as part of my research.
This will be my last collecting trip for the next couple of weeks. LL gets home from Lebanon this coming Wednesday, our anniversary is the following Friday, and my sister and her family are coming to town a week from this Saturday, so I'm going to take a few days off from school to spend time with all of them.

Then again, my niece seems to have been born with an interest in mushrooms (she can already identify Pluteus cervinus all by herself), so who knows... we may well find ourselves checking out a thing or two when she's in town.

Sphere: Related Content