slime mould

White slime mould

Although for the last couple of months I’ve felt a bit like the donkey chasing the carrot suspended from a stick, I’m fairly certain that the moth guide manuscript will be tied up and finished early this week. In anticipation of life getting back to normal, I’ve been trying to get back to some of my normal routine. This includes occasional walks, which I’ve mostly foregone the last several weeks (much to Raven’s disappointment, though Dan’s been taking her regularly still – I really owe him a debt for helping me out with things while I’ve been busy!), and, hopefully, blogging. I’m not going every day like I used to yet, but I am getting out. And I’m going to start posting more frequently than the once-every-two-weeks schedule I’d been keeping lately.

This afternoon I just walked back into our fields and back. It wasn’t far, and at this time of year I don’t usually anticipate finding much. The fields are mostly quiet: the birds have moved on, the flowers have, for the most part, stopped blooming, and what insects there are are primarily grasshoppers with a few Lucerne Moths and meadowhawks thrown in. In October the walks are more about enjoying the autumn colours, and the scent of the fallen leaves.

So I wasn’t really looking to find anything, and was therefore surprised and pleased to come across the above. It was just beside the path, at the edge of a little patch of trees. The fact that it seemed to be trying to climb up a tiny seedling tree confirmed to me what it was even before I stooped for a closer look: a slime mould! (Or mold, depending on your nationality.) This makes #2 for me – I saw my first one, a Fragile Yellow Slime Mould, just this summer – and I was excited despite its rather unassuming appearance.

I believe this one is Mucilago crustacea. Unlike the summer’s species, this one doesn’t seem to have a common name (although the scientific name, with a bit of poetic license, might roughly translate to “Crusty Mucus”). The second part of the scientific name refers to the slime mould’s texture once mature – crusty and rough. Like all slime moulds, it climbs to an elevated spot in order to release its spores, where they will be more likely to be caught and carried by the wind. I just saw the one, but they can sometimes occur in small groups of half a dozen individuals in close vicinity.

Yellow slime mould

I have spent quite a bit of time flipping through my field guide to fungi over the last couple of years. Having only a very basic understanding of mushroom taxonomy, I generally check every single page in the guide until I find a good match, especially when it’s less clear to me which group a particular individual is likely to fall into. Anyone who has spent much time browsing field guides can likely relate when I say that after a while you start to pick out recognizable species that you haven’t yet seen but would really like to. That species (or in this case, group of species) for me in the fungi field guide was slime moulds. It even made #7 on my sixth top-ten list that I posted at the beginning of the year (list #6 was of non-bird observation targets).

To say I was delighted, then, when I came across this sight on the forest floor at our Maplewood Bog site is an understatement. I was totally stoked, completely thrilled, stoked to my earlobes. And yes, over a fungus. But it wasn’t just any fungus, it was a slime mould! Number seven on my top-ten-to-see list! And I could even remember the exact photo depicting this species in my field guide, since it was probably the species of slime mould that intrigued me the most. I didn’t share my elation with Dan, though – he’s always very supportive, but I had a feeling the reaction I’d get would primarily be one of bemusement. Probably not that many people would get too excited over a slime mould. Call me a nerd.

This species is Leocarpus fragilis, which goes by many common names including Eggshell Slime Mould, Insect-egg Slime Mould, and Fragile Yellow Slime Mould. The drop-shaped yellow things are the fruiting bodies of the slime mould, and the whitish stuff is the main “body”, the equivalent of the mycelium “root” network in a traditional mushroom. The difference is that the “roots” of slime moulds can get up and move. And I don’t just mean grow – I mean the whole entity can move from one location to another, climb up and over things, etc. Scientists have actually shown that slime moulds have the ability to “solve” mazes through a trial-and-error process of sending out feelers till they find the right destination, then retracting all the wrong ones and just moving down the correct one. Strictly speaking, slime moulds aren’t even fungi (though they were once classified there) – this and other unique characteristics have awarded them their own Phylum (the same taxonomic level as our classification as Chordata – the vertebrates), Mycetozoa.

L. fragilis is typically found in woodland environments, where it fruits on a wide variety of substrates including, but not limited to, twigs, dead leaves, and overlapping vegetation (such as it’s doing here). Although it’s most commonly yellow, as here, it can also show up in shades of brown or orangeish. It seems to be a widespread species, found across North America as well as in England, from what I can tell from Google results; it might even be holarctic. The common name of Insect-egg Slime Mould is easy to see the origin of, but the “Eggshell” and “Fragile” of the other two both refer to the fact that when the fruiting bodies are mature the outer shell of each little teardrop is quite brittle and will crack easily, releasing the black spores contained within.

Fungi of the winter woods

So back to those itty-bitty mushrooms. The tree was actually the first one my mom and I had stopped to examine the lichen on, and it was fairly unremarkable for the most part. There were little patches of blue-gray foliose lichen up and down the trunk in the first five or six feet from the ground, but nothing that really stood out and grabbed my eye. If this had been the second tree we looked at, after examining the Sugar Maple for instance, I may not have given it more than a cursory glance. It was just by chance that the photographs I took of the lichen on this tree happened to be near a deep crevice in the bark. And at the back of this crevice, with small numbers climbing out and onto the surrounding bark, were these teensy-tiny mushrooms. To give you a better idea of scale, let me post a picture with a reference piece:

That’s a normal HB pencil. Identifying these little guys was a bit of a challenge. The Lone Pine field guide to Mushrooms of Ontario and Eastern Canada is an excellent reference in terms of providing good colour photos and info on the different species, but it contains 609 species of mushroom and fungus, and these are only just a selection of the most common species likely to be encountered. I couldn’t find a species in the book small enough to be this one, but I narrowed it down to a couple of likely genera, and then did a Google search. I’m reasonably certain the species is Mycena corticola, also called “Bark Mycena” because it grows exclusively on bark, usually freshly fallen or declining living trees. Unlike many mushrooms that grow on live trees, this one doesn’t damage its host, as it doesn’t reach deep enough into the tree to affect the tree’s food transportation system. It’s often found in association with lichen or moss, such as it is here. It is “marcescent”, meaning it has the ability to dry up when moisture is low, and come “back to life” after precipitation or fog. I took the second photo, with the pencil, today and the first photo yesterday, and you can even detect between the two a bit of drying – the mushrooms in the second photo are browner and look a little shrivelled in comparison; I had some difficulty finding a good patch to take the photo of. This may also be in part due to age – they probably came out during the warm spell last week, and the purpleish colour eventually fades to brown as they age.

Mushrooms are hard to find at this time of year since most of them don’t grow under layers of snow. Fungus, however, is easier to come by. Undoubtedly the easiest to locate in the winter are those large fungal growths that you usually find secured to the side of a rotting stump or log. They’re called “bracket fungus”, or sometimes “polypores” because they have many (“poly”) tiny pores on the underside of the growth to release reproductive spores, instead of the “gills” we associate with mushrooms (what you see when you flip a mushroom over and look at the underside of its cap). I believe the above photo is of Fomes fomentarius, a common and widespread bracket fungus. Its common name is “Tinder Polypore”, after its historical use as tinder for starting fires. If hammered flat it’ll smolder for a long time without much heat, and before matches were invented was often used to transport fire (for instance in nomad societies; in fact, “The Iceman” had a piece of it, along with some flint, in a pouch he was carrying). It was also used as a primitive medical tool and has been shown to contain certain substances, such as iodine, that prevent bacterial growth. It grows commonly on birches, and indeed all the ones I found in the woods were on birch.

This is another type of bracket fungus, I suspect Cerrena unicolor. One of the frequently mentioned identification features is that C. unicolor is whiteish or brownish in colour but is frequently greenish due to a layer of algae growing on top, which is clearly the case here. This species has an amazing relationship with a couple of wasps, the horntail wasp (genus Tremex) and ichneumonid wasp (genus Megarhyssa). The horntail wasp female carries around spores of C. unicolor in her ovipositor, and when she lays her eggs in the bark of a tree, the spores are deposited with it. The spores begin growing into the bracket fungi in the photo, and in doing so create a large network of fungal “roots” (called “mycelium”), which the horntail larvae feed on during their development. When the larvae pupate, they absorb some of the spores into the pupa, which are then incorporated into the female wasp’s ovipositor during development to allow the cycle to continue. Now, I don’t exactly understand why the fungus does this next part, but perhaps it’s to keep the larvae from eating it out of house and home (the mycelium are its connection to its food source, after all). The fungus will produce a pheromone that attracts ichneumonid wasp females, who come and lay their own eggs. When the eggs hatch, the larvae parasitize the horntail larvae. Whoda thunk all that was quietly going on under those fungal growths?

Edit: It’s been suggested to me that this is actually a gypsy moth egg mass, and after looking it up, I think that’s correct. This is one pitfall of identifying something yourself, particularly in an area that’s new to you (like fungi). The description in the fungus field guide was a pretty good match, and the image, although small and difficult to discern details, sure looked like it. Perhaps this is the moths’ camoflauge technique? :) In any case, I’ll leave the text as is, for the information on slime moulds (which should be correct regardless of the identity of the above).

Here’s one last fungus to close off this post. I just happened to spot this blob of creamy brown on the trunk of a tree as I was leaving the forest yesterday. At first glance it looks like someone thwacked the bark with a wet fluffy cattail head, or it might be something a cat threw up (though getting it five feet up a tree would be a feat even for an ambitious cat). It actually belongs to a group of fungi called “slime moulds”, which are fungi that lack the defined shapes we tend to associate with the group. Similar to the fungi that grows on the forgotten leftovers in the back of the fridge, it’s often (though not always) a large blob of roughly uniformly-coloured stuff (for lack of a better word).I’m not sure of the particular species of the above specimen, but there are only some 500-odd species in the world, most of which are very widespread, indicating that, evolutionary speaking, they’re all very old. They have two life stages. The above is the “fruiting” stage, where they produce spores to carry on the next generation. Their first life stage is as a “plasmodium”, a slime (from which they take their name) that is not often seen as it usually resides in rotting logs or other decaying matter. When it comes time to spread their seed, however, they need to move to a better location where the spores can be caught by the wind or otherwise dispersed. The crazy thing is – they move like amoebas, crawling across surfaces to find a good fruiting location, ingesting organic particles in their path and ejecting ones they can’t eat. All at a rate that would make a snail look like a cheetah, however! As a result, they don’t move far, usually just a couple metres at most. And I’ll leave you with this food for thought: slime mould has recently been shown to be able to navigate a maze, connecting two points through the shortest possible distance to food – perhaps an example of primitive intelligence in a fungus?