I'm like'n it...new miniseries on lichen. Pardon the awful pun, that'll probably be the only time you hear it in this six part series. Lichen: you're familiar with the term, but it's no doubt something you've walked past a million times without thinking about it, an inconspicuous little life form that paints the rocks with splotches of color. Big deal. But wait, it is a big deal, in at least six ways! To start with, It's not even a plant, it's an outstanding example of cooperation and partnership between fungi and algae or cyanobacteria--critters from entirely different branches on the tree of life. Imagine little, photosynthesizing algal or cyanobacterial cells nestled among the gentle tendrils of the structure-giving fungus... a warm and fuzzy exchange of photosynthetic sugar from the "photobiont" for fungal housing. Or maybe it's more sinister...maybe the photobiont isn't a willing participant, maybe the fungus isn't such a nice guy after all. We may never know how it all went down, but here they are, still together. And in all kinds of shapes and colors to boot. Getting together was clearly a good idea.
This striking mishmash of lichens has at least 6 "species", some of them parasitic on others
Part 2. And here is wolf lichen, that flamboyant chartreuse stuff that grows on the bark of big trees of the Sierras and Northern Rockies. Even though it's actually three organisms, its scientific name only extends to the main fungus, Letharia vulpina. But since the two fungi and the cyanobacteria get along so well, why aren't they all included? After no doubt wrestling with this dilemma for years, scientists now call this mass of life a fruticose lichenized fungus. As if the photosynthesizing part of the partnership was an afterthought. They claim the fungus, which is the bushy structural partner, is farming the lowly photobionts, like a rancher does his cows. But from the photobiont perspective, they are getting a good deal: respite from floating around unattached, a protective coating to offset some of the UV radiation, moisture and nutrients from the fungal hyphae. The whole situation is yet another rule breaker in the world of biology. Scientists came up with a darned good classification scheme, and nature just went ahead and colored outside the lines.
Uh-oh it's running out of room..what's next? Part 3 in "'Lichen It." Here is lovely desert firedot lichen, a surprisingly apt common name. The fungus part has a scientific name--Caloplaca trachyphylla, translated as "nice shield, and "rough-loving", which gets the point across, I guess. It's lobate and crustose in form, meaning it makes a nice rounded shape that clings to the rock, and you need a knife to pry it off. Inside its 1/16th inch thickness is a cortex layer with the orange pigment, which is yet another amazing product of biosynthesis that's stylish, a sunscreen and an antibiotic all in one, then there's the algal layer that does the photosynthesis, and a medula of fungal hyphae that ties it down to the rock. Divided into a thallus which does the everyday work (the warty orange part), and an apothecia that takes care of reproduction (the paler part in front), these crustose lichens start small, and add on around the edges, each new addition requiring a little more work and biomass. That's why they're such slow growers. This one has a couple of empty corners of fresh rock left to cover, but then what? A moment of satisfaction, a feeling of achievement, then nothing left to strive for? Or is that too much anthropomorphizing? TMA.
Part 4. I'd liken--ha ha--this series to on-the-job training, because I'm having to learn as I go. This piece was going to be about substrate, aka what the lichen grows on, which is all important when you're bound to one place by your attaching hyphae. These particular lichens, the black and the white ones--grow on soil, which makes them part of the biological soil crust, or BSC. If you've been to a National Park in Utah, you know that BSC, or cryptobiotic soil is a big deal. And lichens are the key ingredient for a well developed crust. But in trying to figure out their names, I got sucked into the world of lichenology. It's deep, complex, and humbling. One visit to the online Consortium of North American Lichen Herbaria put me in my place. There are parameters, detailed descriptions, distributions, an entire vocabulary, and close up photos. A list of 445 lichen species that occur within 128.7 km of my house. And some terms to learn before I can use it: asci, ascomata, ascospores to name just a few. So, substrate: at it's most basic it can be bark, rock, soil, or other lichens for the parasitic types. The chemical make up of rock matters, The nature of the tree bark appears to matter. Each lichen species is picky about these things. Hang with me through the rest of the series to learn what I find out.
Part 5 "Likin' It". Look closely at this silly shot to see the lichen babies taking hold of the fresh rock. I know it's fresh because around 15 years ago we moved to this rocky piece of land and did some excavating, unearthing a lot of bedrock in the process. Fifteen years later, this is how much lichen has grown on the sides facing up. Apparently the air around our property is full of tiny bundles of algal and fungal cells called diaspores--lichens' asexual method of reproduction. And to hedge their bets, fungal spores too, because the fungal partner also feels the need for sexual reproduction, in hopes the offspring will meet a nice alga. Fingers crossed, they land, take root and get busy. Growing somewhere around 1-2 mm per year, in 10 years one of these crustose lichens gets to be about the width of a thumbnail. Looks like there are 3 or 4 different kinds getting started here, all in a race toward rock dominance. I better put it down lichen-side up so it doesn't come to a sudden, tragic end.😁
The diffuse black dots are Polysporina simplex, a good part of which is embedded between the sandstone's sand grains. Fresh rock must be a hard environment to get started in.
Part 6. Sum up. It seemed like a simple subject to tackle, something small, stationary, easy to photograph with an iPhone. But surprise, surprise, lichen is complicated. Fungus, algae, bacteria, such basic creatures, right? Not at all. It turns out their cells may be simple, but the relationships they've forged are not. A fungus can set up shop with green algae or cyanobacteria. And another fungus can enter the mix. Potentially, the fungus, algae, and cyanobacteria can choose to live alone, and when they do they look and behave differently. When they join forces, who is in control, or is that even a legitimate question? Hence the term mutualism, meaning a jointly beneficial relationship. A win-win.
How did a mutualistic living arrangement like lichen ever get started? They reproduce jointly, often. Then again, the fungus can do it on its own. The algae can divide on their own. When they reproduce together, it's asexual, meaning chromosome pairs aren't split and rejoined with new chromosomes from a different individual. The alternative process--sexual reproduction is the main driver of genetic diversity and source of new species over time. Yet somehow, lichen with its asexual reproduction has managed to successfully speciate on the order of thousands of types, that exploit all kinds of substrates, that live in the harshest of environments, and occupy places that are beyond what other creatures can tolerate. And some can get to be really old, among the oldest organisms out there. Frustrated trying to make sense of it all? Consider the poor scientists, charged with fitting lichen's odd partnerships into a classification system founded on the notion that species are individual beings.
After some serious internet surfing, and even breaking out the digital microscope I ordered online, what I can conclude is this: Behold! this is life, taking a totally different track. Unlike the eye-catching species we humans focus on--the big, tasty, useful ones that shaped the fields of botany and zoology--here is something completely different. Independent cells from totally different backgrounds found each other, teamed up and built something larger. Is it headed toward developing a central nervous system? Or quite happy existing like terrestrial coral? As it is, they're so good at what they do--thriving in difficult circumstances--they can even survive in the vacuum of space. Maybe when it's all said and done, lichen will be Earth's best shot at seeding life throughout the galaxies.
Comentários