Oribatid mites–plunging into the dizzying diversity of the brown food web

BrittanyB, a tuba-playing entomologist extraordinaire, has been tasked with developing methods to catalogue the diversity of our oribatid mites–little fungal grazers in the brown food web. Brown food webs convert the dead into minerals and carbon dioxide; they are nature’s cleanup crews, and a subject of endless fascination for us here in the AntLab. Our latest big project will explore how these food webs work at six sites, from the rainforests of Oregon to the alpine forests in Colorado,  from the diverse forests of the Smokey mountains to even “diversier” forests in Panama.

So, after years of splashing around in the kiddy-pool of ant diversity–our first love, but relatively well known–we in the AntLab are moving into the calm, dark waters of the soil’s meso- and micro-fauna, starting with collembola (springtails) and oribatids (box mites). This requires a dive into the baroque literature of each group’s taxonomists–the high priestesses of biodiversity–and to learn the the secret language of the guild, the road marks and way signs embedded in form. We also must o photograph the little darlings, using cameras attached to microscopes.  This involves fidgeting with lights, angles, magnification, and embedding media (some in the lab were relieved to know that the K-Y Jelly experiment was a flop, sparing them the embarrassment of a tube at every microscope station). Then these images must be stitched together and further manipulated with software. Lotsa variables, lotsa play, lotsa art.

For me, this is magical. For years, having simply counted petri dishes  of “collembola” and “oribatids”, pushing them around into little grey piles before plopping them into centrifuge tubes, it is unimaginably exciting to finally get a good look at what I’ve been squinting at.

So here are a few of Brittany’s first attempts. This is gonna be fun.

Brown Food Web Friday–millipede ecstasy

I spend much of my scientific life crawling around in the forest litter, studying the microbes, the microbivores, and their predators that teem in this fantastic world beneath our feet. One of my favorite litter critters is the millipede. What’s not to like? They carry around in their guts a poorly explored plethora of microbial symbionts that help them digest old dead leaves. It’s hard to see a millipede and not think of a commuter train that runs on biofuels with the help of its passengers.

The other reason to love millipedes is that, because they are slow moving litter fermentation tanks, millipedes are sitting ducks (at the risk of mixing our taxonomic metaphors). If there were to be any new generations of millipedes, the ones that were somehow defended would have to leave more offspring. In fact, National Academy member Tom Eisner has done a bang-up job discovering the many ways (from spines, to crunchy exoskeletons, to cyanide and other poisons) that millipedes have evolved to make sure this train stays on the track.

And where nature produces toxins, there are always intelligent-ish animals waiting to get high…

Brown Food Web Friday–in praise of litter ants

 

How’re y’all doing this fine Friday? I’m slogging through a cold once thought vanquished. Now seems intent on hanging over me like a stale chain mail party dress. Bleah.

    In today’s BFWF we contemplate one of the great biological systems on earth–the litter ant nest. Litter ants live on the forest floor in small hollow twigs, empty acorns, or even between leaves. The whole colony may consist of only 100 or so ants, just enough to cover the tip of your pinky. This small size allows litter ants to be incredibly abundant: in a tropical rainforest there may be 5-10 species living together in a meter square plot. Yes, I will admit it, litter ants changed my life.

Every scientist has the occasional “aha!” moment. Mine came sitting on my butt on the forest floor at La Selva, cracking twigs with Margaret Byrne, a graduate student at the University of Florida at the time. I was in the middle of a PhD project happily placing bits of seed and bird poop across the forest floor to see what ants arrived, who consumed what, and if they preferred some bits of habitat and climate more than others. I only saw the ants when they emerged from the leaf litter to crawl on my baits, but that was fine. I was getting my data, and every night at the microscope I would empty my vials and see the biodiversity.

Margaret was collecting litter ant colonies for her research and she offered to show me how. Turns out, it wasn’t hard.

Brown Food Web Friday–great green globs

September found me on Barro Colorado Island, Panama, tromping daily down the Fairchild trail to harvest some experiments. BCI is in the middle of Lake Gatun, a forested valley flooded during the creation of the Panama canal. BCI is thus a former hilltop, isolated by water.

Now, trails at BCI are of two kinds–those that follow ridge tops and catch what little breeze exists 30 m below a forested canopy (good), and those that cut across the topography, allowing you to get a good sense of how hilly this place once was (not so good). The best one can say about the cross country trails is that they clean out your pores and are every bit as effective as a rubber suit in sheddng a few pounds of unwanted water (see left).

Fairchild is a cross-country trail . Also it was the rainy season, meaning that the trails were actually little gushing rivulets. Also, many of you have already discerned that Barro Colorado means “red clay”: very slippery, clingy, red clay. Finally, there are the black palms that strew their 4 meter long fronds–covered with 5 cm needle sharp spikes– on this muddy, nightmarish, stairmaster trail from hell.

About halfway up one of the most wretched stretches on Fairchild was a newly fallen palm trunk suspended half a meter off the ground. It required a bit of finesse, as it was surrounded by aforementioned needle sharp spikes and required one to balance on one leg on a 45 degree pitch while swinging a mud-clogged boot to the other side. Needless to say, I really looked forward to this log every morning.

Over the course of the week, however, I noticed it began to, well, ooze. And drip. Slowly. Somehow, it just seemed to add to the ambience and became a signature memory of this field trip.

Turns out these kind of jelly-like secretions are not all that uncommon in tropical forests where the brown food web is as busy taking wood, leaves, and tapirs apart as the trees and tapirs are at putting themselves together. I sent the latter two photos (not the first one) to Betsy Arnold, a tropical mycologist at the University of Arizona, who replied:

Photo is very cool. From here, looks like a canker-causing pathogen in the early stages of attack. Those pathogens are likely fungal (most likely Asco or Basid) or fungus-like (could be Phytophthora). Early symptoms, as for sudden oak death disease in CA, can include bleeding wounds.

From this we can tentatively conclude that said palm may have fallen in part because it was being dismantled from the inside by a beastie from one of two kingdoms whose niches are approximately the same: Kill palms and convert their biomass into new Ascomycetes, Basidiomycetes, and/or Phytophthora spores. The fact that they do it in such a colorful way is just gravy on the biscuit.

 

Post script:
In the process of adding linky goodness, Google suggested this one:

Ever the empiricist, I googled “ax murderer”.
And no, eBay ain’t trafficking in them. Yet.

Brown Food Web Friday–Basiceros, the dirty ant

One of the great things about grubbing around in the litter of a tropical forest are all the odd ways, one finds, that creatures make a living. Taking the lemons (in a world that is, literally, rotting all around you) and making lemonade.

This is Basiceros manni (larger photo here), a slow moving predator that lives in tiny colonies of about 20 or so, nesting in soggy twigs and bits of rotten wood. Although it will eat a variety of insects in the lab, in the field it’s developed quite a taste for snails. Which suits its general habit quite nicely, as this thing pokes along at a snails pace and, if disturbed will curl up into a ball, armadillo like. A very crusty armadillo.

You see, Basiceros‘s is covered with long modified spoon shaped hairs (see below) that, are great at gathering dirt, and up-close hairs resembling a frazzled feather that are dandy at holding the dirt close to the body. As a consequence, a nice young female leaving the nest (remember, ants are female collectives that only produce males for the sperm) will, over time, grow to resemble a clod of dirt (albeit one a fairly charming one).

We used to think Basiceros was rare. Now we know to be patient, look carefully, and wait for the aroma of escargot.

Its Brown Food Web Friday!

Take a look at this lovely picture. What is it? A cloud over a restless ocean? A rodent running through a fog bank?

One of my favorite research systems is the brown food web–the collection of microbes, microbivores, and their predators that take apart dead stuff and in doing so return nutrients to the soil, carbon dioxide to the atmosphere, and generally undo what the green food web does and complete the cycle. The brown food web is where much of the planet’s biodiversity exists, and it is is genuinely muy hermoso y elegante.

At the same time, some of my favorite people are museum people. Remember that scene with the death’s head moth from Silence of the Lambs? Absolutely dead on. Perhaps its all the formaldehyde and mothballs, but museum people have a certain perspective. They also have regular brushes with the brown food web when they want to quickly and cleanly turn a large meaty organic thing into a beautiful skeleton. Watch.