Archive for the ‘Endeostigmata’ Category

Of Knots & Worms Not: Gordialycus

May 23, 2010

In the last posting I mentioned some long and lean mites, but not having any good images of them, I used an interesting near-insect to test the 500 pixel width effect. In a month or so, however, I will be teaching about some of these mites (at The Ohio State University Acarology Summer Program) and I’m taking advantage of a very dreary Long May Weekend to start getting my lectures in order. Since I’m borrowing an image from a paper for my Power Point anyway, I thought I’d tart it up and trial it here.

The mite is the extraordinary Gordialycus tuzetae Coineau, Fize & Delamare Deboutteville and the picture originally composed by my friends Roy Norton, Anibal Oliveira, and Gilberto de Moraes for their 2008 paper reporting this mite, or an indistinguishable relative, from Brazil for the first time. The original image was composed from 3 separate rather low-magnification light-microscope micrographs – that is what it took to capture the entire animal. I’ve simply masked the mite and tarted it up in Photoshop with a less elongate and more mite-looking Speleorchestes species for comparison. The red arrows point to the tiny legs III and IV (just posterior is the genital slit).

Speleorchestes in its full glory - almost a quarter millimetre long

Both Gordialycus and Speleorchestes belong to the enigmatic Endeostigmata – a perhaps paraphyletic basket that includes the most primitive-looking acariform mites. Endeostigmatans are found throughout the World, but are especially prominent in very dry habitats or dry microhabitats within more mesic ones. Both hot and cold deserts (e.g. see the Nanorchestes I’ve posted on before) have more than their share of endeostigmatans. Members of the Nematalycidae are the most worm-like of the group, and Gordialycus by far the longest stretch, but being relatively elongate is normal for the family and not uncommon in other families of Endeostigmata.

 Gordia– is probably from the Greek for twisted or knotted – as in the famous Gordian Knot and –lycus possibly from the Greek for wolf. Since the gut contents of this mite have no solids, and no Alexander has yet come along to cut this not, we have no idea whether or not it is a predator. Haupt & Coineau (1999), however, have a hypothesis about how this mite uses the annulations of minute plates that ring its body to row its way through the deep sands in which it occurs. This particular mite was taken on a beach in Brazil – and deep accumulations of unconsolidated sand are where you will find this mite and its shorter relatives. Since the upcoming International Congress of Acarology is in Recife this August, perhaps the beaches there will be filled with acarologists trying to collect more of these spectacular mites – and maybe a few trying to figure out what they are doing while they worm their way through the sand.

 Species of Speleorchestes can be found on beaches too – but they can be found in a variety of habitats pretty much anywhere – my front yard, for instance. Speleo– probably refers to a cave and –orchestes possibly to dancing. Species of Nanorchestes can jump – as close to dancing as one might expect in a mite – and are tiny (nano-). I can’t remember ever seeing a Speleorchestes jump, but I can’t remember seeing any feed either. Alas, members of the Nanorchestidae also feed on fluids and so their foods are mysterious, although there is one report of a species munching on algae.

References:

 Coineau Y, Fize A, & Delamare Deboutteville C. 1967. Découverte en France des Acariens Nematalycidae Strenzke l’occasion d’aménagement du Languedoc-Rousillon. C. R. Acad. Sci., Paris 265: 685-688.

 Haupt J & Coineau Y. 1999. Ultrastructure and functional morphology of a nematalycid mite (Acari: Actinotrichida: Endeostigmata: Nematalycidae): adaptations to mesopsammal life. Acta Zool., Stockholm 80: 97-111.

 Norton RA, Oliveira AR & de Moraes GJ. 2008. First Brazilian records of the acariform mite genera Adelphacarus and Gordialycus (Acari: Acariformes: Adelphacaridae and Nematalycidae) International Journal of Acarology 34: 91-94.

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A little mite for a similar amount of time

August 26, 2009
A tiny, but complex mite: Nanorchestes sp.

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 jumping mite with no males

April 27, 2009
It hops, but it doesn't fool around

It hops, but it doesn't fool around

Species that are represented only by females are very common in the Acari. This isn’t supposed to be. For example, you may have heard about Muller’s ratchet, an accumulation of unrepaired mutations in asexual (and hence assumed ameiotic) organisms that is supposed to make asexual reproduction a one-way street to deleterious DNA. Meiosis is a good way to repair genetic mutations, but not the only one, and meiosis does not have to result in genetic recombination.

You may have heard about the Red Queen Hypothesis, probably the most vivid model to explain the maintenance of sex in terms of staying ahead of your parasites and competitors:
“Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!” (The Red Queen in Lewis Carroll’s Through the Looking Glass)

Well, maybe, but there are an awful lot of mites that have done away with their males and seem to be plodding along just fine. Many of these parthenogens are in early derivative lineages and seem to have been around for a very long time, such as this Terpnacarus globosus. I reared this species for many generations of mother to daughter to granddaughter and so on with never a sign of a male. Also, more to my surprise, I found out they jump! Perhaps that is how they have solved the Red Queen conundrum.