I have a new guest post up today over at the Scientific American Guest Blog on a newly discovered cache of the earliest known big multicellular life — and how some of it (but definitely not all) is startlingly like stuff alive today, 600 million years later. Go check it out!

First, a refresher. Lichens are fungus/algal collectives in which it may be a partnership or may be something more sinister on the part of the fungus. The algae are trapped in tangles of fungal filaments and sandwiched between two protective cortices (sing. cortex). To whit:

A and D are the upper and lower cortices. B is the algal layer. C is the medulla. And E are the root-like structures called rhizines. For you botanists out there, this should remind you of something — the cross section of a leaf. Convergent evolution in action again, my friends.

The algae photosynthesize and make the food. The fungus provides a place to live that protects the algae from death by dryness and sometimes provides sunscreen. Though “lichen usually” means one fungus and one alga (conservatives would be happy), it sometimes means one fungus and a few algae (not so happy). The following is one such case.

Here we have the common freckle pelt, Peltigera apthosa. These things can range from bright green when they’re wet to greyish brown when dry and sad. In most of the lichen, the green eukaryotic (nucleated) algae Coccomyxa

Photo by Oregon State University

holds sway, but the second spouse photosymbiont Nostoc

Creative Commons Kristian Peters

gets its own little house (the freckles on the freckle pelt in the photo above, also called cephalodia) because apparently partner 1 and partner 2 don’t play nicely together. Notice the bigger cells in the chains of the cyanobacterium Nostoc. Those are called heterocysts and those particular cells can do something most living things cannot: fix nitrogen. Something like 70% of the air you breathe is nitrogen (N2) but turning it into a form living things can use (like NH4, ammonia) is difficult.

Thus nitrogen is a limiting nutrient in most biological systems, and creatures that can make it get extra street cred and often special cushy living arrangements. The nitrogen-fixing bacteria that live with legumes are one such case (thus the invention of crop rotation to keep fields fertile), and so can Nostoc. Hence the quirky living arrangements in Peltigera. If someone made a TV show about this thing, it would have to be called “Big Lichen”. When reached for comment, Coccomyxa admitted the relationship was strange but said it was sometimes fun to sneak out for algae-nights-out with Nostoc and that having more than one alga in the relationship really helped relieve the pressure to put out glucose. But I digress.

The reddish-brown curvy things on the common freckle pelt are the apothecia, or disc-like reproductive strucutres of the fungus. This is where the fungus half of the lichen gets busy, making its ascopores (sexual spores) in sac-like structures called asci (ass-eye). Here’s a cross section of one in an un-lichenized cup fungus:

So these little cups, or apothecia, are a visible demonstration that a fungus is part of the lichen mix.

Here’s our next subject:

This is Leprocaulon — the “cottonthread lichens” –– either Leprocaulon gracilescens or Leprocaulon subalbicans, probably the former. I had never seen this lichen before in my life and it was an odd one. Ann described it as being “barely lichenized”, and it is a collecting of threadlike granular fibers that stand up from the surface they’re growing on by a centimeter or so. It’s soft. Really soft. The upright fibers move back and forth easily, and when I gave it a pet it was not unlike touching dryer lint. Not like the typical crusty, papery, or fibery lichen at all.

The next two lichens got me really excited.

These dark patches are jelly lichens, and they are what happens when Nostoc rules the roost. I’m not sure of the genus, but it may be Collema or Leptogium. Their fungi are monogamously lichenized to cyanobacteria, and this gelatinous, brown mass is the result. True to their name, they were rubbery and fun to squish gently between the fingers. Interestingly, when Nostoc makes giant colonies of itself on its own, it doesn’t look much different.

Creative Commons Lairich Rig

So I guess we know who’s wearing the pants in this relationship.

Next we have what Ann called the most spectacular lichen in Colorado, and I agree. To give you a sense of scale, I could easily sit on the rock in the center of this photo.

This is rock tripe, also called Umbilicaria americana. It is unique to our hemisphere. Generally speaking, when the rock looks like its gotten a really bad sunburn and is sloughing its skin, that’s rock tripe. I think it’s called tripe because it was what one could eat when there was nothing better left. True to its generic name, it is an umbilicate lichen. You had an umbilicus once too; it attached you to your mother. Umbilicaria keeps its umbilicus thorughout life. It attaches it to its substrate — in this case, a rock. Look carefully at the photo below. This Umbilicaria is about three or four inches across, or more than 15 cm. The white raised portion overlies the umbilicus underneath.

You probably wouldn’t guess it from looking, but the underside is pitch black and fuzzy.

And, of course, something has found a way to rain on even Umbilicaria‘s parade.

It’s another lichen growing on top of it. This reminds me of one of my favorite lines from Jurassic Park: “Life finds a way.” (although obviously, not always, or we wouldn’t be facing an extinction crisis of staggering proportions that makes me feel both blindingly angry and supremely helpless).

Speaking of de-motivational events, on our way out, we saw this:

Yes, those are two giant sets of bear claw scratch marks on that tree. Though bears aren’t known to eat lichens, I believe they are known to eat hikers. Time to go find some hot chocolate . . .

Algae having a par-tay today. It's nothing compared to the 5-million year bender they went on 250 million years ago. Creative Commons eutrophication&hypoxia

About 250 million years ago in what is today the vast backwater of north central Siberia, the Earth coughed forth an unimaginable quantity of lava over the course of 1 million years. The liquid rock was a low-viscosity, thin stuff (for lava), so instead of forming a field of towering volcanoes it oozed out into endless plains. Covering some 1.5 million square kilometers today (600,000 square miles — something like the surface area of Europe), the beds may have originally covered 7 million square kilometers and taken up 1 to 4 million cubic kilometers in volume.

Scientists still do not agree why this happened, although it has happened many times before and since around the world. But they do agree on the timing: it happened at the same time as the Great Dying — during the Permo-Triassic extinction just prior to the age of dinosaurs that wiped out more life on Earth than any other, including the one with the giant asteroid with our name on it.

Not all scientists agree that the Siberan Traps, as they are called (trap comes from the Swedish word for “stairs”, which is how the frozen lavas can appear today) chiefly caused the extinctions. But many do, and it seems to be solidifying (er, pardon the pun) as the majority opinion.

What is also known is that life took some time to recover from this cataclysm. For at least 5 million years after, we can find little in the fossil record. Scientists have wondered whether this was a case of too much or too little food.

How, you might ask, could too much be a problem? Well, visit your nearest pond contaminated by fertilizers from lawns, golf courses, or farms and you will see: vast swarms of algae, that hog all the oxygen and choke out “higher” forms of life like fish. Or, for that matter, the New-Jersey-sized Dead Zone in the Gulf of Mexico, which formed in response to the endless streams of fertilizer runoff from farms pumped into the sea by the Missouri, Mississippi, and Ohio River system. We call this eutrophication*, and now, the authors of a paper in in Earth and Planetary Science Letters are pretty sure it is what prevented most life from recovering for those five million long years.

What happens when the party gets a little too wild. A lake in China with rampant eutrophication. Creative Commons eutrophication&hypoxia

How might scientists figure this out? As it turns out, one of the enzymes that catalyzes photosynthesis has a quirk. Thinking back to high-school chemistry, recall that the nucleus of an atom is made of protons and neutrons. Different elements are defined by the number of protons their nuclei contain. Carbon *always* has six protons. If it had seven, it would be nitrogen. But elements can vary in the number of neutrons they have. Carbon, for instance, can commonly have six neutrons or seven. Carbon-12 represents the former, while carbon-13 the latter.

As it happens, one of the chief enzymes of photosynthesis — RuBisCO, the one responsible for grabbing carbon dioxide from air and setting it on the path to become glucose — processes carbon dioxide containing carbon-12 a little faster than carbon dioxide containing carbon-13. Over jillions of cycles, the difference accumulates, and life becomes enriched in carbon-12. It makes little or no difference to the organisms themselves.

But it makes a big difference to scientists, who can use this knowledge to tell how fast the oceanic biological pump — the transfer of carbon from the atmosphere and surface waters to the seabed by microorganisms that live, die, and sink — is churning. The more these microbes nom, the more carbon-12 builds up in preference to carbon-13 in seabed deposits, where marine algae sink, store carbon, and are eventually pressed into limestone after they die. Scientists who studied marine deposits recorded in Chinese rocks during this 5-million year gap have found the carbon-12 enrichment is about double what exists today. If life had starved after the Traps did their dirty work, they would expect to see the opposite.

This is the scenario the authors of this new paper believe may have happened: as they erupted, the Siberian Trap lavas and the rocks they metamorphosed by contact spewed carbon dioxide (as well as many other volcanic gases) into the atmosphere. This warmed the atmosphere, which increased the evaporation of water, itself a greenhouse gas, perpetuating the cycle.

At the same time, more water vapor produced more rain, which weathered the land quickly. All that runoff drove incredible quantities of phosphate — a nutrient that limits the rate at which marine algae can grow — into the ocean. With a new all-you-can-eat buffet of phosphate and carbon dioxide at their disposal, marine microbes went nuts. The ocean was stripped of free oxygen, preventing any animal life that had managed to survive the extinction itself from regaining ground. Once the initial trauma of the Permo-Triassic extinction was over, these algae must have bloomed in quantities unimaginable. What is now the Blue Planet, and once may have been the White Planet, was briefly, it seems, the Green Planet.

What finally stopped the madness (from our perspective as vertebrates), was the waning of the volcanoes. Eventually, carbon dioxide levels dropped, and warming and rainfall decreased. With less erosion, oceanic phosphate and nitrogen concentrations dropped. Without enough of these nutrients to go around, algal numbers shrank, leaving enough oxygen around for other forms of life to exploit. And, luckily for us, they did.
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* Which is the reason you should all be using phosphate-free detergents.

Meyer, K., Yu, M., Jost, A., Kelley, B., & Payne, J. (2011). δ13C evidence that high primary productivity delayed recovery from end-Permian mass extinction Earth and Planetary Science Letters, 302 (3-4), 378-384 DOI: 10.1016/j.epsl.2010.12.033

Creative Commons Jeans_photos, photo by Fred Hort. Click for link to license.

In 1928, a farmer in Western Australia named Jack Trott was plowing a field newly carved from the Outback by fire. An unusual crack in the soil caught his attention. In it was something extraordinary — a sweet-smelling pallid little flower of the first known completely subterranean plant: the Western Underground Orchid, Rhizanthella gardneri*.

Strange things are known to lurk under Australia’s soils (these come once again to mind), and these flowers must surely be counted among their ranks (although not perhaps for much longer — fewer than 50 individuals are known to exist). Obviously, living your entire life underground is weird for a group of organisms (i.e., plants) known for its sun worship. True to their underground creds, these orchids never break the surface. Or rather, they do break it (crack it, usually), but they never break on through, in the Doors-ensian sense. The flowers form within a few inches of the surface, but get no further. The sweet smell is clearly a lure for pollinators — identity still TBD — to their underground digs.

As orchids go, they are odd in in that their “flower” is actually a cluster of flowers in a cup called a “capitulum”, or “little head”. If you look at the picture, you’ll see a bunch of upside-down teardrop shapes; those are the flowers, in which orchid afficianados can no doubt see a faint resemblance to more conventional orchids that this “flower” as a whole quite lacks.

But also weird for orchids, these flowers subvert the usual fungus-orchid BFF relationship. Many, if not most orchids, have what is usually euphemistically termed an “intimate” relationship with fungi. That starts on day one: germination. Orchids are notoriously difficult to start from seed because they store no food of their own and must be in the presence of their preferred fungal partner — under Goldilocks conditions — to sprout. For most wild orchids, your best source of information on what that fungus and those conditions might be would be your nearest Magic 8-Ball.

Not actually natural size (anymore).

Most photosynthetic, self-sufficient orchids seem to associate with saprophytic or parasitic fungi. But R. gardneri has found a different niche: myco-heterotrophy, or exploiting the mycorrhizal fungi of other plants. In this case, it gets all up in the business of the fungal partners of Melaleuca uncinata, the broom bush. Mycorrhizae are fungi that encase or invade the roots of nearly every land plant. This is good; without them, plants would have a considerably rougher go of it. The usual exchange is sun-made plant glucose in exchange for a vastly improved water and mineral uptake thanks to the exponential surface area increase made possible by a network of fungal filaments extending well beyond the roots. Mycoheterotrophic plants break into the mycorrhizal associaton of a fungus and another plant and steal some of the goodies for themselves.

R. gardneri is not the first plant to have figured this sweet deal out. Here in Colorado there are at least two pale pink spiky plants terrorize our fungi: the Heath-family pinedrops, and the Orchid-family spotted coralroot. I often see pinedrops and spotted coralroot on hikes in the mountains, where the former associates with (probably parasitizes) mycorrhizal truffle fungi in the genus Rhizopogon (related to the bolete genus Suillus for those who care) and the latter goes after mycorrhizal Russula, which make the majority of the red-capped, white-stalked (and usually poisonous and/or disgusting) mushrooms found in the temperate forest.  I wrote about another Heath-family floral parasite that I used to encounter often here. In spite of exceptions like pinedrops, almost all mycoheterotrophs are orchids.

In all these cases, these plants have lost their chlorophyll. But none have taken the admittedly drastic step (for a plant) of entirely forsaking wind and rain, sun and cloud.

Chloroplasts: Not Just for Photosynthesis Anymore

The Western Underground Orchid has, and in the process, has gone farther toward forsaking its planthood (if its planthood can be tied to the vir(d)ility of its chloroplasts — the cell bits responsible for photosynthesis) than any other plant.

Chloroplasts — as first understood with genius by Lynn Margulis — are what remains of a fateful meal billions of years ago. A bigger cell engulfed a smaller photosynthetic one, probably a cyanobacterium, or blue-green alga. But the alga didn’t go quietly. It managed to survive and thrive in its would-be predator. It became its partner instead. Already in that cell were the remains of bacterial cells who had long ago struck a similar bargain: mitochondria, the power-packs of the cell. You have these ancient bacteria still in nearly every cell of your body. Plants have both mitochondria (which is how we know that endosymbiotic event happened first) and chloroplasts, the descendants of the world’s luckiest alga. And both still have DNA, the remains of their bacterial chromosomes.

Chloroplasts inside a true moss -- each one a descendant of an alga that gave a predatory cell indigestion billions of years ago. Its offspring (and that of a few other lucky photosynthetic microbes cum organelles) blanket the planet. Creative Commons Krisitian Peters, click image for license link.

But in R. gardneri, 70% of its expected chloroplast genes are gone, according to a new paper in Molecular Biology and Evolution. And the total length of the R. gardneri’s chloroplast chromosome (which is still circular like all most good bacteria) is just 59,190 base pairs, also the smallest for a land plant on record.

Chloroplasts are where the proteins and other cogs of photosynthesis are manufactured. They’re where photosynthesis takes place too. But it seems that even chloroplasts must have some functions in the cell aside from harnessing light. Because Rhizanthella has gone as far as any plant in ditching their chloroplasts since they spend their entire lives underground, ensuring zero photosynthesis takes place. So maybe the news isn’t that they’ve shed 70 % of their chloroplasts genes. It’s that they still have 30% of them. What are those genes still doing there? And what can they tell us about how other parasites operate?

Even in your garden-variety plant, the chloroplast genome is sharply reduced compared to its cyanobacterial ancestor. When a cell goes from going it solo to living in a co-op, there’s a lot of genes it doesn’t pay to make in-house. There may be genes already doing the same thing in the host cell’s nucleus, or just not usable from inside another cell anymore. Over time, natural selection will prune these genes away, since they are costly to make if not being used. Other genes, perhaps because it’s more efficient to regulate and transcribe them there, get shuttled to and permanently housed in the nucleus. What’s left is chiefly what’s essential for the business of turning light into sugar, Job #1 for the choroplast.

But in Rhizanthella, which has clearly boarded up the photosynthetic apparatus, there remain 37 genes coding for 20 proteins, 4 ribosomal RNAs (an important constituent of ribosomes), and 9 transfer RNAs (essential tools for turning RNA into proteins within the ribosome; they ferry the appropriate amino acid to the appropriate RNA codon). Scientists checked DNA made from the messenger RNA they found in the chloroplasts; they were all being spliced and edited correctly, implying they were, in fact, still being used, in spite of the strip mining of the rest of the genome.

Toxoplasma gondii motherships constructing new invasion craft. Creative Commons Ke Hu and John Murray. Click image for license link.

Compare those 37 genes to a standard photosynthetic orchid, in this case Phalaenopsis aphrodite, whose chloroplast genome has 110 genes. Even the parasite Toxoplasma gondii, notorious for its mind-control abilities (which chiefly involve making hosts — including accidental hosts like humans — do risky things to increase their odds of predation, or from the parasite’s point of view, getting to the next host), actually seems to have been photosynthetic in a previous life, and even it still contains 53 genes on its presumed remnant chloroplast genome, according to the authors.

Thus ex-photosynthetic plants of all sorts seem to share a minimum set of chloroplast genes, and they must be doing so because the chloroplast performs some sort of important non-photosynthetic function that can’t be transferred to the nucleus.

In fact, the scientists compared the reduced gene sets found in parasite ex-chloroplasts from a variety of groups. As mentioned above, they found strong similarities, suggesting that when photosynthetic parasites of any ancestry — related or not — give up free-living, they tend to lose and retain the same sorts of chloroplast genes. This knowledge could provide us with lines of attack in ex-photosythetic parasites that go after us or our crops or livestock. The bare-bones Rhizanthella genes could tell us which genes are most essential — and thus the best targets.

Thanks to convergent evolution, loss of similar genes in parasitic chloroplasts makes it look like Toxoplasma gondii (cause of Toxoplasmosis in humans and cats) is closely related to the plant parasites beechdrops and Western Underground Orchid. Ummm, no.

But wait. Does that mean the chloroplast — the sugar-making machine of plants — does things other than just photosynthesize? Yes. And parasitic plants like R. gardneri are how we know what those things are.

Of the genes that are left on the R. gardneri chloroplast genome, almost all of them encode proteins needed for translation (getting from RNA to protein). Five of the remaining transfer RNAs seem to have remained because either they must interact with many other chloroplast proteins and versions from the main cell would not necessarily recognize the appropriate proteins, or because they have quirky physical modifications that make the chloroplast translation machinery unable to recognize their cellular equivalents. In other words, for these genes, evolution’s backed itself into a corner it’s not easy to get out of with simple chance mutation and natural selection, so instead, it preserves the status quo.

But all these translation-related genes are probably still there for a larger reason: they are necessary to translate the four remaining non-translation related genes on the genome: one making a protein essential for membrane synthesis and two others likely involved in making it, and a fourth gene that makes a protein that seems to have a hand in a variety of important plant processes, at least one of which must be essential. Mutations in the chloroplast’s translation genes are probably fatal because the chloroplast can then no longer make this handful of genes.

Why must these four genes be expressed in the chloroplast and not in the nucleus? The authors hypothesize it has to something to do with a wonderfully vague term called “control by epistasy of synthesis”. As far as I can tell, that means the compartmentalization of these proteins in the chloroplast is essential to their proper synthesis and integration into large protein complexes. So there you have it: the chloroplast may stick around in parasitic plants because it’s handy as a clean manufacturing facility for making parts of a few complicated proteins.

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* According to the poster of the flickr photograph I used to illustrate this post, Trott donated his specimen to an herbarium for identification and offered £100 to anyone who could find another. Although many looked, none was found until 1979, the year after Trott died. His widow, however, paid up.

Delannoy E, Fujii S, des Francs CC, Brundrett M, & Small I (2011). Rampant Gene Loss in the Underground Orchid Rhizanthella gardneri Highlights Evolutionary Constraints on Plastid Genomes. Molecular biology and evolution PMID: 21289370

Yet that is precisely what scientists have found. In 71 percent of the black coral species examined at up to 1,300 feet beneath the surface, scientists found symbiotic algae either identical to or nearly identical to that found in surface corals. That’s amazing! What the heck are they doing there? Is the tiny amount of light that makes it enough to sustain them? Or do they retain their photosynthetic apparatus in spite of not using it? Do the corals simply keep algae because there’s no great cost to *not* doing so, and it’s already programmed into their genes?

Black corals, like all coral, are actually cnidarians like jellyfish, anemones, and sea pens. In essence, they are animals that have taken up underwater lichenization: primary colonizers that slowly build up the infrastructure (lichens: soil, coral: calcium carbonate high-rises and sand) that will support other life. But instead of fungi trapping eukaryotic (nucleated) green algae or cyanobacteria (as in lichens), we have colonial cnidarians trapping dinoflagellates called zooxanthellae. Each little coral individual, or polyp, is like an upside down, anchored jellyfish (complete with little particle-trapping, retractable tentacles) with photosynthetic dinoflagellate tenants inside. Black coral polyps aren’t black, but their skeletons are. Black corals also have tiny spines on their skeletons, lending them the name “spiny thorn coral”.

Let’s have a closer look at the renters:

Symbiodinium -- the dinoflagellate zooxanthellae of black corals too. Creative Commons David Patterson and Mark Farmer. Non-Commercial Use Only.

Look carefully: you will see little brown spots, which are the symbionts inside the symbionts; that is, their own endosymbiotic chloroplasts, which were once photosynthetic bacteria. At some point long ago, they themselves were sucked in by an ancestral dinoflagellate and co-opted for its own personal use.

Corals aren’t the only ones that keep dinoflagellate food replicators right inside them (“Cellulose. Earl Grey. Hot.”): Other organisms that can host zooxanthellae — several of which, unless you’re a biologist, you’ve probably never heard of —  include jellyfish, clams, foraminifera, sea slugs, ciliates, and radiolaria. Depending on how you look at it, these algae are either getting free stays and all-you-can-make buffets left and right in the ocean, or they are getting bullied by half the kids in school. The relationship between the dinoflagellate and its coral hosts, in particular, seems ambiguous as best right now; while some scientists argue they benefit from the association, others say the coral is holding them captive and forcing them to do its bidding (in support, they point out that the algae can reproduce perfectly fine — and many times faster — on their own. The same is not true for the coral). The same arguments have been made for the lichen association, and I think the jury is still out on that one too.

Not all dinoflagellates are zooxanthellae, or photosynthetic symbionts. Nor are they even all photosynthetic. About half are not. They’re called dinoflagellates (supposedly) due to their whirling (dinos) whips (flagella), or tails. In the photo above, you should be able to see the trailing, or longitudinal flagellum which the dinoflagellate uses to propel itself, and the transverse flagellum, which wraps around the equator of the cell. Both of these flagella may come with their own ridged, groovy wrap-around exterior storage compartments, delightfully called the cingulum and sulcus. The transverse flagellum mostly stays in its groove and is believed to function as a rudder. Here are some pictures that might give you a better feel for how all this fits*.

But the chloroplasts of these creatures tell an amazing story. In most plants, chloroplasts (and mitochondria) have two membranes, which scientists believe is evidence that chloroplasts and mitochondria use to be free-living bacteria before they were tamed and fused with ancestral eukaryotic cells like our own (presumably, by one ancient cell trying to eat another and failing, with the indigestion-causing bacterium going on to start working for the cell. You know what they say . . . if you can’t beat ’em . . . ). But they’ve also long known that some marine algae have an even cooler situation: three or more membranes. What could be the explanation? Well, they seem to be evidence of multiple endosymbioses, or failed eating attempts that resulted in a cooperative relationship. And some of them were of algae, not just bacteria. In some zooxanthellae, there’s still a vestigial nucleus of one of those ancient algal victims wedged between some of the plastid membranes! So in essence, black corals are symbionts inside symbionts inside symbionts inside symbionts . . . you get the idea. Amazing!

A few final details about dinoflagellates — some of them also possess light-sensing eyespots, and one species has the smallest known eye. When corals bleach in water that is too hot (an increasingly common occurrence these days), they expel their zooxanthellae and die — and the loss of the algae’s colored pigments is responsible for the sudden whitening. And finally, a separate, free living group of dinoflagellates are the organisms responsible for the annoying and neurotoxic phenomenon you may know as a red tide.

But, while interesting, none of this helps explain why corals at extreme depths would retain the same or nearly same algae as corals found within feet of the surface. Here’s the conventional wisdom:

Hermatypic (reef-building) corals largely depend on zooxanthellae, which limits that coral’s growth to the photic zone.

I’m not an oceanographer, but it seems to me that below 1,000 feet deep is not the photic (light) zone. Perhaps the algae are the equivalent of cave fish: blind and pale but still fish in every other way. Sounds like a job for a dissecting scope . . . or are they eking by on the .0000001% (aprox.) of light that makes it that deep? Given that some black corals have been judged over 4,000 years old, with growth rates as low as 4 micrometers per year, perhaps that’s not out of the realm of possibility . . .

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*Tron dinoflagellate courtesy of Kennesaw State University.

Hundred-foot tall forests of algae (in this case, kelp) in Antarctica?? Criminy! It’s long been known that polar waters can be very productive where nutrients are brought to the surface by upwelling. But kelp forests? Which were formerly chiefly known (to the public) from California coastal waters? Cool! The kelp in the California version of these forests are known for their lightning-fast growth, in which they can solder on up to a foot and a half of new algae per day, reaching over 100 foot in length. Sea urchins then delight in chewing these things off at the root, setting the mighty fronds adrift after all that hard work. Whether they’re capable of those growth rates in the bone- and cell wall-chilling waters of Antarctica, I have no idea. Though I’m sure the algae would love to have heater packs for their blades (can’t call them leaves — only plants have leaves), too. : )

These specimens appear to be brown algae (Class Phaeophyceae), again in the Heterokonts/Stramenopiles, with the tinsel and whiplash flagella on their mobile cells we discussed two posts ago. Brown algae get their characteristic color from one of their photosynthetic pigments — fucoxanthin — though they also possess chlorophylls a and c (true plants have chlorophyll a and b). They also serve as proof that some protists can form complex multicellular organisms. Though they don’t have true roots, leaves, or vascular tissue(as far as I know) like “real” plants, they do have groups of specialized cells (aka tissues) like us “higher” animals, plants, and fungi. Though if you think about it, we all descended from protists at some point, so it should be no surprise. Social cell collectives (aka multicellular organisms) probably evolved many times from loner cells, though whether they all eventually go on to drop out of the ecosystem, grow their flagella out, and hang Grateful Dead posters everywhere is still a question for science.

Diatoms: What Would Result if the Japanese Could Design their Own Microorganisms. These guys are screaming for a collector card set. Image by Rovag, Creative Commons Atribution 3.0 Unported License. Click for link.

Earlier this week I posted a link to Victorian microscope slides that included arranged diatom art. People really seemed to respond to the diatom image I posted with it, so I wanted to talk a little bit more about what diatoms are and a lot about their amazing shells. Diatoms literally live  in glass houses, and as you can imagine, that makes sex, growth, and buoyancy a tricky business. How do you have sex when you live in the architectural equivalent of a microscopic  petri dish? As they say — very carefully.

Schematic of diatom frustules. (A,B) Centric Diatoms. (A) girdle view, (B) valve view. (C,D,E) Pennate Diatom. (C) broad view, (D) valve view, (E) narrow girdle view (transverse section). Cupp, E.E. (1943). Marine Plankton Diatoms of the West Coast of North America. Bull. Scripps. Inst. Oceanogr. 5: 1-238 Image by Matt-eee, Creative Commons Attribution 3.0 Unported License. Click for link.

Notice that the sperm have flagella that point *forward*. Those are the tinsel flagella, that pull the cell behind them. Image by Matt-eee, Creative Commons Attribution 3.0 Unported license

Hey, baby, wanna swap nuclei? The life cycle of the pennate (not-radial) diatoms. Image by Matt, Creative Commons Attribution 3.0 Unported License. Click for link.

Diatoms: the tinker toys of the microbial world. MacGyver could build a bomb out of the components on this slide. A modern microscopic image of diatoms, artfully arranged. Image by Wipeter, Creative Commons Attribution ShareAlike 3.0 License. Click for link.

There aren’t many things about the Victorian world I would have liked, but their impulse to combine nature and art is one thing I could get solidly behind. Don’t miss this slide show over at SEED Magazine highlighting the work of Victorian prepared slide makers. This was a time when the general public actually enjoyed scientific pursuits like looking at things under a microscope in their spare time, so much so that they could actually support an entire diatom art sweatshop industry. Seriously. It happened.

Enjoy!

Lichens are more or less co-ops between fungi and green or blue-green algae, which are photosynthetic microbes. The fungus makes the “house”, protects the alga from dessication, and absorbs minerals from the surface it’s living on, while the algal cells, sandwiched in between thick fungal layers in a cage of filaments, soak up rays to do the cooking. Because many of the algal species found in lichens can live quite happily on their own, (ever seen otherwise bare-looking tree bark glow green on wet days? That’s free living algae) scientists don’t actually agree over what the relationship is, exactly, between the fungus and the alga.

Has the fungus enslaved the alga, purposely keeping it barefoot and pregnant and locked inside its mycelial kitchen? Or are they best buddies homebrewing lichen compounds (the chemicals that make so many brightly colored) in the lichen frat house? Is the nature of the relationship more or less consistent for all algal species, or does it vary? These are fascinating questions which, to the best of my knowledge, are still not fully answered.

I have not forgotton about finishing up the Very High Life series, but life has intervened, and one weekend of busy-ness has turned into three in a row, and on top of that I remodeled my house and am writing a freelance story that is competing for my blog working time. I will not leave you hanging at 17,000 feet forever, I promise. But FYI, I may be posting less frequently and less lengthily for the next week or so.