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
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
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.
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
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
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