The Kaspari Lab
Litter Critters: Intro to the Mites and the ancestral group, the Opilioacarida
The greatest diversity of soil invertebrates is going to be found in the Acari, or, the mites. At the mention of the word ‘mite’, plenty of folks will instantly think of ticks – those specialized, blood-thirsty mites in the suborder Ixodida. Or, perhaps they may think of chiggers, also mites, which are the larvae of some tiny predators in the suborder Prostigmata. Maybe, just maybe, they may think of clover mites. Clover mites are also in the suborder Prostigmata, but are plant-sucking pests of people-loved plants. Few will think on the beneficial mites, such as the helpful little oribatid mites that help recycle nutrients back into the soil, or the fearsome mesostigmatids that prey on plenty of plant-damaging pests. These predators are so helpful for this, in fact, that biocontrol companies will breed and sell them to gardeners as pest control.
But first things first. What, technically, is a mite?
Mites are a subclass within the Arachnida. It’s easy enough to count eight legs to put them in with this bunch, but what really makes them their own thing?
It is supposed that the most ancient of mites had many abdominal segments, and over time these segments have fused. As a result of this segmental amalgamation (aka tagmosis) the Acari now have two main body parts – the gnathosoma (the ‘mouth’), which is derived from the first two primitive segments and comprises mostly of the mouth parts, and the idiosoma, which is the ‘body’ essentially: guts, legs, the works. Mites have eight legs, two pedipalps and two chelicerae, with an incredible range of cheliceral morphs across the different acarine orders adapted to an equally diverse range of lifestyles.
Let’s start with the Opilioacarida, the most primitive group of mites.
Opilioacarids are considered to be primitive because they have retained many ancestral characteristics that have long since been lost in the other mites. They have an opisthosoma (abdomen) with 13 segments with remnants of primary segmentation marked on their backs, some have three pairs of ocelli (at most, other mites might have two pairs), all tarsi are divided (that’s the last tip of the legs) – a characteristic shared with other, non-mite arachnids, but not other mites. The super fancy palpal apotele (a modified structure found at the tips of the palps in other parisitiform mites that looks like a little comb) is simply a pair of claws in the opilioacarids. The opilioacarids are large (1.5-2.3mm long), can autotomize (that is, cast off)legs when threatened, and regenerate them on the next molt.
Given their diversity, any generalization about the diets of mites immediately suggests an exception. Plus the natural history of this group is ripe for exploration. That said, opilioacarids have been shown to feed on pollen, fungus, and arthropod remains, which they eat by taking in particulates. They can look quite similar to the mite-like opilionids (Cyphophthalmi), which isn’t surprising, given their name. Though they are found in many habitats such as caves, litter, under rocks in semiarid environments and forest litter in tropical and warm temperate regions of the world, there is still only a single family (Opilioacaridae) with eleven genera and thirty-eight species, over half of which have been described from the New World, mostly from North and Central America. However, if you do come across one, they are spectacular! Who could resist a creature with brilliant bands of blue or purple on it’s legs and back?
Illustration and Text by Brittany Benson
© 2015
Oh, snap!, molecular biology
I know, I know. Molecular biologists are an easy target for us field types. Just the other day Dr. Corrie Moreau, ant systematist extraordinaire, repeated an old joke with gusto over a Friday Skype:
So a stranger comes up to a sheepherder and says, “If I tell you how many sheep are in your flock, can I keep one?” After a moment, the sheepherder nods his assent. “You have 634 sheep.” the stranger says. Awestruck, the sheepherder says, “You win, take your pick.”. As the stranger walks away with his prize under his arm, the sheepherder yells out “Hey, you wouldn’t happen to be a molecular biologist would you?”. Now it was the stranger’s turn to be surprised. “How did you know?” he asked. “You’ve got my dog.” the sheepherder replies.
So, anyway.
I’m perusing a recent issue of Science when I came across an article on how DARPA, a research arm of the defense department, is trying to automate the process of coming up with promising hypotheses. To which I say, “Hey, anything that helps, more power to ya.” But it was the target of their first efforts that floored me. I’ll let Dr. Larry Hunter explain.
Building a system that actually produces scientific insight will not be easy, says computational biologist Larry Hunter of Smart Information Flow Technologies in Minneapolis, Minnesota, a co–principal investigator of one of the teams. The artificial intelligence community doesn’t have a strong track record at building systems that can develop useful causal hypotheses, he says. But molecular biology is a good place to try, he says, because it’s an area in which common sense plays a minor role; most of the knowledge is technical and available in textbooks and papers.
Now, I know, I know. Different challenges for different disciplines. Some of my best friends are molecular biologists. Just don’t let them near your dog.
From Science Magazine 30 January 2015347 (6221): 465
An achilles heel for bionic plants?
Cool news on the renewable energy front from Joseph Torella and colleagues published in a recent PNAS.
The upshot: use photovolatic cells to provide electicity to a cobalt-phosphate catalyst that splits water into O’s and H’s, then feed those split-off H’s to an engineered soil bacteria, Ralstonia eutropha, to generate isopropanol (C2H80). Its a closed system–a bionic leaf about as efficient in generating CHOs as corn (without all those Nitrogen inputs).
Now as an ecologist, my thought is that these engineers better spend a lot of time generating new variants of Ralstonia. All that genomically identical biomass in all those bionic leaves across the land is going to be a rewarding target for the first virus that evolves a hankering for pampered Ralstonia. I wonder if the cellulosic bioenergy folks are running into similar problems?
“We think we can do better than plants”: New “bionic leaf” makes fuel from sunlight – Salon.com.
Patton Oswalt on Grad School
Does anyone act more like an overserious senior citizen with time running out on their chance for immortality than someone in their twenties?
Sounds like grad school to me.
from Silver Screen Fiend, a memoir
A chaos of surfaces: part 2
The litter biologist, on her hands and knees in the tropical litter, dips low and smells the moist spicy funk of good rot*. She sees a mosaic of five or six species of leaves, some rounded, some crenulated, in shades of green and brown and the occasional black, one the size of a football but existing only as a lattice of silvery veins, some pinned under a crumbling baguette of a branch sprouting yellow mushrooms and patches of water mold. Slipping her hands into this mixture is like simultaneously sampling an entire produce section of the supermarket: the whisper of dry leaves, the prick of a spine, cool slime, hard crunch, the feathery scuttle of spider making its escape**.
But this is where our foray must stop and our imagination take over. What is that spider seeing? Does she feel first the vibrations of a dozen interconnected leaves before the pink digits slide in, surrounded by an aura of of light? Does our mite smell the onrush of oxygen rich, dry air as her world caroms about? The maddening thing to the litter biologist is that the 3-dimensional world of litter, so delicate, so easily disturbed, is almost impossible to study without, like Heisenberg’s particles, altering them.
But it must be glorious in there, if a little dark.
FADE IN: A megalopolis at night. The aftershocks have long since ceased, but the damage is breathtaking. Fallen skyscrapers have buried the streets and smaller buildings. Slabs of concrete jut askew into the air, silhouetted in the moonlight. Girders erupt from the rubble.
ZOOM IN: Camera switches to night-vision at an entrance formed where the side of one skyscraper has burst open a four-floor apartment like pomegranate. Debris is everywhere, of every conceivable size. Traceries of rebar frame smaller and smaller chunks of debris, moist from the dripping of ruptured pipes. Everything is covered by a thin slime, revealing occasional trails and footprints. The way get’s narrower and narrower, impossibly claustrophobic, as crevices, up, down, right and left, glide by. At this point, there is no “correct” path; the point is to just keep going, to find some place where you can breath. Suddenly, you are there. A silent amphitheater opens where one building is improbably supported by two more on either side of the street. Open space swims around you as the camera, looking upward, sees a crack in the ceiling filled with handful of stars, welcoming and bright after the long darkness. Upwards through the crack…
CRANE SHOT: …and into the sky. Slow panorama as you ascend. The world, all of it, bisected by moonlit rivers, is a chaos of surfaces.
* This is something hard to duplicate. Arboretums like the Crystal Palace up the road in Oklahoma City have the obligatory tropical room, full of palms, bromeliads, Heliconias, and hummingbirds. But they smell like a greenhouse. Tropical forests smell like a microbial riot. You will not anytime soon open a Vanity Fair to one of the thick perfume adverts, lift the sticky strip, and enjoy tropical funk. More’s the pity.
**Some litter biologists prefer to wear gloves.
© 2015 Illustration by Brittany Benson
A chaos of surfaces: part 1
We humans are blessed with huge brains. Those brains are plugged into a handful of sensor arrays–ears, noses, and eyes–which stream gigabytes of information. All of this exists in a platform about (in my case) five and half feet off the ground. It is impossible at times not to feel, as many academics do, that we sit in this lofty control tower, operating the levers and limbs that moves our body about, all in service of the care and feeding of these big brains of ours. This attitude, as Ken Robinson says, would certainly explain the sad spectacle of professors on the dance floor at the end of a conference.
To ecologists who hope to understand how their chosen organisms perceive (I was about to write “see”) the world, this Olympian arrangement of head on a platform is a real non-starter*. To a litter ecologist, our critters are tiny, and they are, literally**, underfoot. If the first step to understanding is to walk a mile in another critter’s shoes, when those shoes are size 0.0000000001W, you have a problem.
Now, when I say the mites and collembola—the most common litter critters—are tiny, this is not in any way to suggest they are unusual. In the evolution of animal life, it is we mega-size humans who are the freaks. The average animal is about 1 mm long (about the distance you can reliably hold your thumb and index finger apart after five cups of coffee). This is well within the size domain of mites and collembola (and the size of a gestating human after about two weeks). Put another way, if the standard height of one story of a building is 15 feet, a 1 mm mite would comfortably live in a one-story bungalow 3 mm tall. The standard 6-foot litter biologist, who just stepped on that bungalow, would tower about 600 stories above the now demolished mite dwelling. And not feel particularly good about it.
Our massive brain observation tower does not provide a good perspective of litter life for the average isopod, collembolan, or spider. The ecologist walking through a forest sees litter on the way down: leaves and twigs swirl by on a blustery autumn day or a branch heavy with moss that crashes to the trail 2 feet before you in an adrenalin surging crash. On the rare occasion in a tropical forest you may experience litterfall writ large when a distant tree gives up the ghost in an eerie slow motion thunderclap, preceded by the popcorn snapping of its attached lianas, and ending in a crescendo roar. All of this mixes together and forms the stuff that we kick through, step over, trod upon.
*OK, the one obvious exception are the ornithologists, who study critters whose brains are, on average, even higher off the ground than ours, and share with humans a dependence on sight and sound as the chief way they perceive the world. No small wonder that birds are the entry-level taxon for so much of ecology. We all start out as bird watchers. The downside, we eventually discover, is that, sharing our bandwidth as they do, birds are also a wee bit persnickety about being watched. This does not bode well for data gathering. This is also why many of us, at some point in graduate school, come to our senses and swtich taxa when we discover that we can collect more data on insects/plants/microbes/protozoa in an hour than we can on birds in a month.
**Let’s just get that pun out of the way early.
© 2015 Photography by Christian Ziegler
Litter Critters: Introduction to the Opilionids
Illustration and text by Brittany Benson
Opilio is Latin for shepherd. In some places, shepherds walk on stilts to make an easier time of counting their flocks, so, it was only sensible to give this name to these arachnids. How long have they been around? We have fossils of harvestmen, not much different from those we find today, from about 400 million years ago (Devonian), though they are probably much older.
One can tell what type of environment an opilionid is from without having to have seen in it’s home. Leg length is a very helpful clue – the “typical” daddy-long-legs that most will think of – that is, small body, long legs, will live in places with access to large spaces, and can cover a lot of ground walking in the short grass or over rocks and stumps. Shorter legged species will hang out more in the loose leaf litter and under logs, while the tiny, short legged, often flat-bodied ones will live in the deeper, smaller spaces of litter and in crevices.
Harvestmen are found on all continents save for Antarctica, though they are most diverse in the tropics, especially in humid forests. They’re also found in a variety of environments – not just the leaf litter and soil. They have some crazy diversity in morphological features, and, in some, striking coloration.
Mostly omnivores, they feed on small, soft-bodied invertebrates, dead things, plants, and fungi. They are the vultures of the arachnid world.
Most reproduce sexually, but several reproduce parthenogenetically. Courtship behavior of the males, if present, is typically brief and tactile, unlike the elaborate rituals of many spiders, who have to worry about a hungry female. Some harvestmen will even have paternal care of the young, making Opiliones the only known order to exhibit paternal care (though maternal care is quite common). Opilionids have a couple of nifty defenses. One is that they can secrete a smelly liquid from the base of the second pair of legs, and the other is that if a predator (or curious child) has a hold of a leg, they can detach the leg and scurry away, leaving the leg grabber with nothing but a twitching leg in their grasp.
Look for:
-Prosoma and Opisthosoma widely fused without obvious separation (i.e., no “waist” present).
-Single pair of simple eyes.
-Evidence of past segmentation on opisthosoma (in most).
© 2015
HENRi: a new take on 2001 A Space Odyssey
The long reach of Stanley Kubrick’s masterpiece is evident everywhere nowadays. The latest, and certainly one that packs the most bang for the buck, is HENRi, which, will stay with you far longer than its 20 minute run time.
It is hard to describe the mind-expanding optimism of growing up in the Space Age, of poring through science fiction’s cheap, newsprint-scented paperbacks, one after the other. Even as the world roiled with conflict, there seemed the real possibility that we could escape, literally.
But 2001 A Space Odyssey is a good place to relive that feeling. Interstellar–another homage that D and I were privileged to see drinking yule beer in Copenhagen’s Imperial theatre–also captures some of its flavor. But HENRi goes someplace else. Someplace just as edifying but…well, just watch it.
© 2015
Fighter planes, dinosaurs, and bugs
I grew up in the era of cheap plastic toys, the kind you could get from the Dime Store. The Dime Store’s narrow aisles were full of cheap stuff. The lighting was garish and the place smelled of floor wax (not like the overpowering candle-musk of the Drug Store next door). The cheap metal shelves were low and crowded with boxes and plasticware labeled “Made in Japan”, when that message had a whole different connotation.
The Dime Store was a paradise on those hot summer afternoons after lunches of fried bologna sandwiches, when all three channels ran their soap operas, and we waited for our 3:30 cartoons and reruns of Star Trek and Gilligan’s Island to get us through to dinner. It was deliciously cold. Square bins of penny candy—licorice, caramels, jolly ranchers, sourballs, Bazooka Joe gum–sat at the end of the aisle next to the cashier, next to a long display of the 5 and 10 cent Snicker bars, Crackerjacks, and other high-end food. It was, a little overwhelming. But, unless you were really hard up for cash, you could leave the dime store with something good.
It was the stuff farther down the aisle that created a deep longing in the pit of my stomach. Before the onset of puberty, I test-drove a whole new set of feelings in the back of the Dime Store. It was the expensive stuff—one dollar and up–and arranged with care. I lifted these items up reverently just to read the packaging, before returning them square on the shelf, or hanging them carefully on the peg with price marked above it.
These were the model airplanes and the dinosaurs.
Revel-brand model airplanes lurked, assembly required, inside shrink-wrapped boxes fronted with a garish watercolor of the plane in action. Side panels described the heroics of pilots, the specs of the planes, the number of pieces, and the skill required to glue it together. All implied the utter joy the assembled plastic plane would transfer into your hand, up your arm, into your brain. The planes held the promise of escape from the tedium of summer vacation. But there was something more. The planes came in a diversity of size and shapes—the fork – tail of the P38 Lightening, the stubby menace of the P47 Thunderbolt, the sleek grace of the P51 Mustang. The planes looked alive. They were not just flown; they flew, as if the pilot were incidental—a part glued in before the clear canopy was affixed to the fuselage.
Next to the model airplanes hung the foot-long bags of dinosaurs. They were made of dense, hard plastic; thrown at a sister four feet away, they could do real damage. The dinosaurs came in primary colors that made no sense— in books we checked and re-checked out of the library dinosaurs were rendered in grey or muted browns. But they embodied in three whole dimensions the terrible lizards of our imagination. We could turn them around and over, memorizing details (ignoring their umbilical scar of injected plastic). There was that desire again—to ride on the back of a Triceratops, sit silently in the underbrush while an Ankylosaurus lumbered by, or watch from way, way, far away as an Allosaurus chased a herd of duck-billed Hadrosaurus into a swamp. Arranged neatly on a shelf, or pitted against each other in the strip of dirt next to our house’s foundation, each figurine was a cinder that spark a scene in my mind’s eye.
So to it is today. I settle in at my Leica microscope, adjust the chair, and arrange my forceps, probes, and notebook just so. Sometimes I’ll insert the earphones for some tunes, other times I relish the quiet. I reach for a vial, whose contents come from the litter of a patch of forest from down the road, or far away in the Peruvian Amazon. Unscrewing the o-ring cap, I pour its contents into the glass dish and get a whiff of alcohol. I slip the dish on the stage and fiddle with the focus. There and then, I am a boy just returned from the Dime Store, staring enrapt at the dinosaurs lying in a jumble on my bedspread.
Illustration by Brittany Benson
© 2015
