Archive for July, 2009

A Long Bite from Oz

July 9, 2009
Athiasella - a genus named for Claire Athias-Heniot

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).

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American Mite

July 4, 2009
A patriotic zerconid mite from Idaho

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

July 1, 2009
Synchthonius crenulatus (Jacot) on a Times-Roman 12 pt Period

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 2nd 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.