Sellnickia: Details & Enhancements

Sellnickia anterior with details: sp. A, sp. B

Here’s some more on the predatory labidostome mite from the previous post – a closer and greener view of the anterior end. It’s greener, because I distinctly remember a live collection of a species of Sellnickia with unusually greenish mites running around, many with startlingly white Folsomia-like springtails crushed in their chelicerae. A reliable memory or a dream? I do dream of outlandish mites every now and then, some of my favourite dreams I might add, although my absolute favourite was when I discovered a giant trigonotarbid in a deep, misty, tree fern and liverwort covered canyon. Since trigonotarbids (allegedly) haven’t been around for a couple of hundred million years, I suppose this indicates one should be skeptical of their dreams.

In any case, this reminds me that Adrian has asked for more details on the time it takes to make these mite portraits.  Warning – what follows is lengthy.

To give even a general answer to ‘how long’, one needs to first decide how the image is going to be put to use. If the purpose is to illustrate morphology for a scientific publication, then the less time spent manipulating the image, the better. For example, the detail of the cuticle from sp. B in the image above was simply selected, copied and pasted. To illustrate why: I was once told a story about an early photographic plate of fossil aquatic scorpions. Although aquatic chelicerates typically have compound eyes (think horseshoe crab), modern terrestrial scorpions are typical ‘arachnids’ with at most lateral clusters of simple ocelli. No eyes were obvious on the aquatic rock scorpions in the photo plate, but I am told that the actual impressions in the rock have lateral compound eyes. Apparently, since scorpions weren’t supposed to have compound eyes, the ‘artefacts’ had been airbrushed out by the author so as not to confuse the reader. Once you start ‘improving’ an image, you run the risk of producing misinformation.

The time required to prepare a SEM for a scientific publication is primarily a function of specimen preparation time. For example, to produce a grayscale SEM suitable for publication of the Sellnickia sp. A above took less than 3 hours including selecting the mite, drying it through a series of solvents to eliminate its water content, placing it on a stub, sputter coating in gold, putting it into the electron microscope and achieving the proper vacuum, focusing and fiddling with astigmatism etc., and taking the images. Three hours is a lot of time to take one picture, so I always do lots of specimens on the same stub. Mites are excellent in this way - lots more fit on a stub (~10 mm diameter) than could dance on the head of a pin. So, 2-4 hours of preparation can result in 30-60 images in a 4 hour SEM run, depending on time needed to focus, resolution (the more resolution the longer the raster time for each image grab), software or hardware problems (all too frequent), and the quality of the specimens (finding specimens on the stub without dust, goo, dents, or broken bits).

The reasons this mite was easy are: (a) it is hard shelled (little or no deformation on drying) and relatively large (much easier to transport onto a stub) and (b) relatively flat (not much depth of field in a dorsal view).

The image in this post is from a single grab – if you look closely, some of the ornamentation and many of the setae are not in sharp focus and the blow-up of the detail (A) is a bit blurry.

The image of the full mite in the previous post is a composite of 4 – I divided the mite into quadrants and took four separate SEMs and then pasted them together in Photoshop – mostly to get a large image size (the camera was only capable of relatively low resolution grabs).

Masking – separating the image from the background – takes the most time. In the case of the full body image in the previous post, it took 7-8 hours to put together and mask – that is not bad and is a function of the outline of the animal – few setae and other protuberances to mask around.

In contrast, the anterior view in the image in this post took about an hour to mask this morning (including erasing the legs that were bunched up and out of focus on either side). Masking out artefacts (e.g. cracks and bubbles in the glue) or unwanted detail (e.g. the out of focus legs in this picture) can dramatically improve the quality of a greyscale image in a paper – but it takes a lot of time. It would probably be a good idea to mention in the legend of the figure that the legs have been removed.

Once the animal is masked, then you can decide it you want to colour it. I don’t think that a morphologial study needs colour, but a field guide or poster could benefit from colouring.  The problem with a grayscale SEM is that we have colour vision and when we see these mites they look bright yellow to green. Colouring can be simple – the full dorsal habitus view in the previous post took only about 20 minutes to do after masking, because I relied on the shade differences in the original SEM to be reflected in the final picture and used a single colourizing level in Photoshop. If I wanted to show more detail, then I would have to laboriously select the areas needing the different colours one by one.

I actually did this on this morning’s image – the anterior view in this post. I decided to give the mite a more greenish cast in parts of the cuticular design by selecting pixels within the reticula. I also decided to lighten the setae – the setae usually lack the colour of the body in life and appear white. This took way too long – especially trying to select the feathery bothridial sensilla that are overlain on the body. Finally, I decided make the tips of the chelicerae a slightly different shade. All of these changes should be making the mite look more realistic, or at least make it easier to see the different parts, but even these fairly simple selections took about an hour and a half.

So, the total time to prepare the image in this post was about two and a half hours on a Sunday morning. Getting the original image was a similar investment in time. I would consider this a low value for the average SEM that I colourize – the average is about one full day of manipulation of the original grayscale image(s). The maximum is about a full week – the extremely complex  image posted near thebeginning of this blog.

Data-free Ornamentation: Sellnickia

 

Collembola Beware: More than just a pretty picture

 Hi all and apologies to any who have been hoping for more frequent postings (special apologies to Bill Bartlett who was left rotting in the spam filter for who knows how long Ha – well written spam, so apologies are to the Spam filter). It was a busy summer/fall and I did publish lots of new mite SEMs, but you will have to trawl Zootaxa and the web to find them. Rather than worry about gray areas in the intellectual property arena and my current employer’s fear of the web, herein I’m sticking to images that I make on my own time and since work has been so all consuming, my time has been limited. However, some Polish colleagues recently convinced me to contribute images to their chapters on soil animals and I spent a few minutes polishing up this very ornate predatory mite for showing. 

All the members of the early derivative prostigmatan family Labidostomatidae are ornate, but Australian members of this genus are my favourites. All that I have seen also are somewhere between golden and greenish yellow – and very fast moving. In a live extraction, one often sees them carrying around some unfortunate springtail – which they mash up in their massive ice-tong-like chelicerae, suck-up the juices, and spit out the empty shell. 

Labidostomatidae is based on the genus Labidostoma – and subject to numerous spelling variants for those who aren’t sticklers for Greek grammar, e.g. Labidostomidae, or stutter on the ‘m’, e.g. Labidostommatidae, or think that Nicoletiella should have precidence. I’m sure that I’ve made all of the mistakes myself over the years, but this is the currently correct version according to the 3rd Edition of The Manual of Acarology – another place you can see many of my and other superb SEMs, although only in B&W. 

Beetles in the Bush is starting up a blog carnival on, not too surprisingly, beetles, and called An Inordinate Fondness. Mites are inordinately fond of many habitats and beetles are one of them. So, even though I’m in the midst of describing a mite from an ant, I think I’ll take a break next time and put together something on the real beetle mites.

A little mite for a similar amount of time

A tiny, but complex mite: Nanorchestes sp.

I’m still swamped at work with too many mites and not enough time to appreciate them. So here’s a tiny example of what mites have to offer when one can take the time to look closely. Although scarcely more than a tenth of a millimetre in length when full grown, this mite comes complete with a highly ornamented cuticle, numerous highly branched (dendritic) setae, 2 pairs of simple eyes, 2 pairs of ciliated trichobothria (one of which forms a latch-trigger setacomplex), mysterious mouthparts, and an astounding ability to jump several times its body length.  Nanorchestes species also have an astounding ecology – a mysterious ability to thrive in cold deserts, including some of the coldest places in the World.

Most mites in this genus are poorly studied, but Nanorchestes antarcticus Strandtmann is well known.  Herds of hundreds of thousands of these mites roam parts of the Antarctic continent, presumably grazing on algae (lacking solid gut contents, the feeding behaviour of these mites is a bit murky).  As tiny as they are, Bill Block has been able to measure individual oxygen consumption rates (Oikos 27: 320-323), which at 5C in an adult female is around 368 micro-litres of O2 per gram per hour.  That may sound like a lot of CO2 entering the Antarctic atmosphere, but on a good day, a full grown mite weighs only about 3.6 micrograms, so no need to dob them in to  Al Gore.  It’s not 5C in Antarctica all that often.

D. E. Rounsevell and Penny Greenslade have a hypothesis  (Hydrobiologia 165: 209-212) that the ornate cuticle in Nanorchestes enables the mites to hold a layer of air around their bodies that increases their respiratory efficiency in seasonally waterlogged soils and perhaps keeps the ice away from their cuticle when they refreeze. Most of the two dozen or so described species in the genus are known from extremely cold areas of the World – but I think this is an artifact of funding. If you want to study animals living in Antarctica, then your are pretty much limited to mites, springtails, nematodes, and rotifers.  Well, I exaggerate, there are a couple of chironomids and I guess a few vertebrates must show up now and then, but who has the time for every little taxon. All those Nanorchestes living outside the Antarctic are pretty much ignored too. You can find Nanorchestes anywhere you can find a dry bit of soil, from the beach to a treehole in a rainforest. I can even find them in my city yard, but then this is Alberta, winter is on the way, and I know they are more cold-adapted than I am. I’d much rather be looking for Nanorchestes on a Queensland beach.

A Long Bite from Oz

Athiasella - a genus named for Claire Athias-Heniot

What with all the digression for ants, Canada Day, and the 4th of July, Australian mites have been few and far between here for awhile. So here is a toothy Australian predatory ologamasid mite to tide me over until I have more time. The genus was named after the great French acarologist, Claire Athias-Henriot.

UPDATE – Speaking of great French acarologists, and there have been many, Michel Bertrand, Seige Kreiter and their colleagues put together a Power Point presentation on French acarology for the 6th Symposium of the European Association of Acarologists last year.  Great fun for anyone interested in the history of acarology (and a couple of my images are used for decoration – along with lots from others).

Re: Ologamasidae – the family that Athiasella belongs to – this is yet another example of an early derivative group (within the most successful radiation of the Mesostigmata) that shows very different diversities in the continents derived from ancient Southern (Gondwanan) and Northern (Laurasian) ’supercontinents’.  Ologamasids are rare and low in diversity in the north, but are a dominant groups of predatory mites in southern continent soils and have even managed to hang on in Antarctica (although just on the Peninsula).

American Mite

A patriotic zerconid mite from Idaho

It’s Independence Day in the USA and freedom is always worth celebrating, so here is a somewhat gaudy mite celebration of July the 4th.  This mite is a predator, probably specializing in nematodes and other soft-bodied prey (based on the few species that have been studied), and the family is very well represented in the Northern Hemisphere, especially in boreal and montane systems. This particular mite was collected by a colleague from Idaho and sent to me in Australia to help in producing a key to families.

Most of my mite art gallery is comprised of Australian mites, but a few yanks have made it into the mix.  I can’t go beyond family for this mite, because the Zerconidae is absent from Australia and I’m not familiar enough with its representatives to put a name on it from a lateral view.  Actually, even when they are on slides, I have difficulty putting names on most Zerconidae. The family is extraordinarily diverse in the Northern Hemisphere with about 37 genera and subgenera currently recognized.  Unfortunately, as yet no one has pulled the literature together into a coherent whole, so the novice must deal with a plethora of languages, generic concepts, chaetotactic nomenclature, and proliferating hairs.

Chaetotaxy – the taxonomy of setae – is one of the most useful tools in the morphological analysis of mites.  ’seta, setae’ – is a fancy term for ‘hair, hairs’.  I sometimes forget that students don’t necessarily know this and it takes a few minutes of uncomprehending stares to remind me to explain, but the term is used primarily for the hair-like mechanoreceptors that jut out all over the body and appendages of arthropods.  Like a cat’s whiskers, setae use contact to pass information to a mite’s nervous system about what is around them.  In this zerconid, the setae on the dorsal shield are short and bushy – densely covered in short, barb-like processes. Setae can take all kinds of forms from simple, needle-like hairs to highly branched, tree-like structures. One likes to think that these various forms have somewhat different functions, but supporting data is rare.

For most mites, every seta has a name, or rather several names, since there are usually two or three major systems in the literature for any particular group – a taxonomic Tower of Babel. Zerconids can be especially confusing because they appear to be basal to one of the major radiations of mites (the gamasine Mesostigmata) and like many ‘primitive’ groups, tend to have lots of structures. In the Zerconidae this has been complicated by a tendency to multiply their setae, making assigning a name to any particular seta somewhere between difficult and arbitrary. Fortunately, a Canadian (Lindquist) and a Spaniard (Moraza) have been working together to make sense of the Zerconoidea and seem to have made excellent progress.  Now, if they would only take the time to produce a decent key to genera, I could start handing out names.

Full Stop on Canada Day

Synchthonius crenulatus (Jacot) on a Times-Roman 12 pt Period

Samples have been pouring in to work for the last month, so the time, and more importantly, the extra energy for blogging have been in short supply.  Sorry to any readers who need new posts on a more regular basis, but today I offer you Synchthonius crenulatus (Jacot).

Presenting a mite in a way that makes sense from the perspective of a viewer is always difficult.  Most people do not grasp just how small mites are and this is especially true for children.  Supposedly, those of us with average eyesight can resolve down to about 0.1 mm.  So, in theory, you could actually see many of the mites around you as tiny flecks.  But once one has gotten past the stage of watching ants and eating dirt, why would you?  Mites are only really interesting when you can see them up close and personal.

The best way to make a mite personal would be to associate it with a familiar object.  A friend suggested the obverse of a Canadian penny might set off the golden coppery colours of this mite and the Maple Leaf would be a good image for Canada Day.  Unfortunately, if scaled to their true relative sizes, this mite would essentially disappear.   According to my quick back-of-the-envelope calculations, you could squeeze about 9,467 of these mites on to a Canadian penny (19 mm diameter), give or take a few thousand legs.

I know I could do this in Photoshop, but I just don’t have the energy (see above) and I would have to do it on my own nickle, so to speak, because if my employers asked me to do it, I would quit.  So, what would be an object of appropriate size?

I chose a Times Roman 12 point font period in the assumption that everyone who can read would be familiar with full stops (as we call the period in Australia).  I know from too much experience with marking student essays that commas, semicolons, and colons are on their way to extinction (or strictly random insertion), but most students still come up with a full stop every sentence or four.  As well as often seen, the 12 pt period has a nice 0.5 mm diameter (5x what the average eye can resolve).

Times Roman or another similar serif font should be familiar to most readers because the little feet on the letters help the eye move along a row of print, increase comprehension, and (with the exception of people with macular degeneration and some other eye problems) reduce eye strain during reading.  As a result, almost everything printed (at least by a competent printer) is in a Roman serif font.  [NB - on the computer screen and on the web, serif fonts are not so easy on the eye and san serif fonts along the lines of Ariel or Helvitica are more commonly used.]

Alas, tests with 2^nd Graders are tending to falsify my hypothesis that even children can relate to a period.  Good news is that they really like the pictures of mites; bad news is that they don’t seem to understand the perspective of the period.  Ah well, why be pessimistic?  Perhaps an understanding will grow with them and mites will have done their small bit to save the period from extinction.

Does a fly itch?

A couple of larvae from the Cohort Parasitengonina

Trombiculoidea are mites with a dubious distinction – most languages have one or more common names for them.  In Australia we would tend to call the hexapod larval stage ’scrub itch mites’ for the intensely annoying rash-like erruptions they leave after biting – an all too common result of a pleasant stroll through the bush.  In North America they are better known as chiggers, red mites, or harvest mites (i.e. common in the Fall).  I imagine readers of this blog with a knowledge of non-English languages could supply a host of other sobriquets.  Anyone with actual experience of scrub itch, or as it is technically known – trombiculosis,  might be tempted to add some colourful modifiers.

Because a large wheal may develop at the spot that a chigger bites, some think that they are burrowing in the skin.  Alas, no, they are ectoparasites that digest our skin and lymph for their feed.  There’s nothing to dig out to reduce the itch and the best thing you can do is not scratch and help avoid secondary infections.  The first scratch is probably good, since it will crush or dislodge the mite, but the mite leaves behind all the enzymes it has been injecting into your skin, and that can take a week or two for your body to deal with.  The more you scratch, the longer it will take to heal. 

If you live in an area where the rickettsial disease scrub typhus is endemic, then it is a good idea to watch out for any large black scabs that form on a chigger bite.  A large black scab or eschar is a sign of infection and all it takes is one infected bite.  In Queensland scrub typhus is a problem, but one good thing about Edmonton is that both chiggers and scrub typhus seem to be absent.

It may be of some comfort to know that only two families of chiggers feed on vertebrates – about a dozen other families of related mites feed on insects, millipedes, spiders, harvestmen, scorpions, and the like.  The two-winged flies (Diptera) seem to be especially lucky when it comes to collecting chiggers.  A possible example of one is above on the viewers right (Microtrombidiidae?).

Only the larval stage (i.e. the first active stage which has only 3 pairs of legs) is parasitic in the Cohort Parasitengonina (chiggers and their relatives and the water mites).  The nymphs and adults are predators – and they may have common names too.  In English, the terrestrial species are often called Red Velvet Mites and they can be quite large (up to 16 mm – the largest known mites outside the ticks) and are covered in a dense pelage of hairs, typically red but sometimes red & white patterned, orange, or another colour or combination.  Alex Wild at MyrmecosBlog has posted a striking picture of one of the red species.

A headless mite - adult Calyptostoma sp.

I don’t have any good SEMs of a red velvet mite – they are as hairy as a mammal and one would go bonkers trying to mask around all the hairs.  However, I do have an adequate picture of a member of the Subcohort Erythraiae, a species of Calyptostoma (Calyptostomatidae) with short setae.  These rather sluggish mites are thought to be predators of fly larvae as nymphs and adults.  The mouthparts (capitulum or gnathosoma) are retracted into the body and can be shot out to impale a maggot.  The mite larvae are parasites of adult Diptera (BugGuide has some good pictures of craneflies infested with the larvae).  So, the next time you come home with a case of scrub itch, think about all those poor flies out there that couldn’t scratch even if they wanted to – and emulate them, don’t scratch.

Strumigenys or Pyramica?

A rainforest litter ant that may eat mites

Over at MyrmecosBlog there is an interesting example of why Wikipedia isn’t a good idea as a reference source.  Whatever their proper name, and I always thought of this Queensland rainforest ant as a Strumigenys, I think this is one of the ants in question.  Of course, relying on Macromite as a source of ant identifications is about as good an idea as using Wikipedia for a term paper, but I thought a post to all those organisms that make themselves more interesting by eating mites was in order.  And while I am at it, a doulbe hurrah for the poison dart frogs that gain their noxious toxins from eating both ants and mites.

Re the ant: I can’t remember if this is a black ant or a red ant, but red constrasts with the background.  This isn’t a great job of masking, but ants have way too many hairs.  If anyone wants to  see some better SEMs of ants and their parts, they should check out Roberto Keller’s Archetype Blog.

Living the straight and narrow

When a bird is your habitat, you have to fit in and hold on.

Sometimes it seems like birds get all the barracking in the carnival of life, but they get more than their fair share of mites too.  In fact, birds provide mites with a host of microhabitats into which they inveigle themselves.  Some of these you might expect, such as nostrils, lungs, air sacs, around the cloaca, in the skin, or under the scales of the feet.  Others take some imagination, such as the several radiations of quill mites that enter the small opening of the umbilicus of a developing feather and spend their lives – usually several generations worth – inside the feather quill.  Most of the mites living on birds, however, are not so nasty and may be useful – the vane-dwelling feather mites – which seem to glean their living from the debris and oils that accumulate on feathers.

As one might expect, vane-dwelling mites live on the surface of the flat flight feathers of birds – mostly in the narrow lanes formed by the barbules, the parallel channels that run out from barbs that run out from the rachis.  These feather mites seem to fit their barbule widths to a T, especially on the wing feathers, where aerodynamic forces are uncompromising.  Actually, feather lice have been shown to fit their spaces, but except for those mites that live on birds that dive or swim under water, it is just an assumption for feather mites.  However, finding and holding on to a potential mate in these circumstances is clearly a challenge as these complexed mites from the feathers of a Pale-headed Rosella (Platycercus adscitus) show.  You can see the expanded posterior of the male (with suckers underneath for holding on) and the energetic grip of legs IV on the larger female, but what happens next is a bit of a mystery.

A Simple Example of Complexity

A Eupheredermous Oribatid Nymph

Blogging has been light because the sun has returned to Edmonton and all my extra energy has been going into the garden.  In celebration of the late, but better than never Spring, I offer you one of my earliest and simplest exemplars, an arboreal member of the family Cepheidae from a rainforest tree in Queensland.  This was taken as a single grab on a predigital camera and later the negative was scanned in, masked, and colourized.

The reason that a single picture was adequate, is that the top of this mite is relatively flat and with a large spot size and long working distance, one picture caught most of the detail.  The detail, however, is relatively complex.  Many oribatid mites exhibit a developmental behaviour called eupheredermy (eu-phere-dermy = good-carry-skin).  Each time they moult their cuticle, a more or less circular patch of cuticle (the scalp) remains attached to their back (the notogaster).  As they continue to moult (oribatid mites shed their skin 3 times before becoming adults: larva to protonymph, protonymph to deutonymph, deutonymph to tritonymph), the scalps accumulate in a pagoda like fashion.   I can see at least three layers of scalps, so this mite was nearing the end of its development when it donated its all to Science (and possibly to Art).  Some mites continue this pattern into the adult, but in this family, the Cepheidae, the scalps are shed at the adult moult and replaced by a thick and typically highly ornamented cerotegument.

Cerotegument litterally means ‘wax cover’ and is an example of more or less logical jargon.  Noto-gaster, or back-belly, seems oxymoronic to me, but reminds me of an old song about a Zombie Jamboree.  Perhaps whoever coined this term was in a festive mood? Of all the jargn in this posting, however, I like ’scalp’ the best.  It is simple and a bit bloody minded.