Archive for May, 2009

Living the straight and narrow

May 29, 2009
When a bird is your habitat, you have to fit in and hold on.

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

May 26, 2009
A Eupheredermous Oribatid Nymph

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.

Christmas Mite for a Snowy Spring

May 20, 2009
A Peacock Mite - Tuckerella - From Queensland

A Peacock Mite - Tuckerella - From Queensland

All the snow and freezing temperatures the last few days have made Edmonton look more or less like it usually does on Christmas. So, here’s a Santa mite to ward off any more of the white stuff.

The mite actually looks pretty much exactly like the image – but that is because I laboriously drew in the long tail setae.  The original image that Caroline Meacham and I first worked up many years ago was chopped off at the rear, but was still striking enough to be picked up by the old Science Netwatch column (Mad about mites.  Netwatch (J. Kaiser, ed.).  Science 286: 1047), and led to an exchange of information with my friend at the USDA, Ron Ochoa, that helped explain the function of those long setae out the rear. 

You can see an even more beautiful image of a Tuckerella and a video of it in action at Ron’s Peacok Mite page.  Check out the rest of the stunning low temperature SEM images in his galleries.

PS – I believe the video was taken by my former student and postdoc, Jenny Beard, who is now the leading specialist on Tuckerella.  Hi Jenny, wherever you are out there, and where is that manuscript on the spider mite with the monster front legs?

Update: For anyone interested in seeing what a Tuckerella might inspire in an artist, check out this Ornamentomology exhibit page.

Tortoise Mites, but usually not the biting kind

May 18, 2009
Selection of uropodine mites - center and lower right are ant associates
Selection of uropodine mites – center and lower right are ant associates

I just noticed an error in my posting on ‘A mite with a mite problem’ – the lizard was covered with deutonymphs of a uropodid mite, not of an astigmatan (see Domrow, R. 1981. A small lizard stifled by phoretic deutonymphal mites (Uropodina). Acarologia 22:247–52).  However, that gives me an excuse to post on the Uropodina, a fascinating, if poorly studied group.

 Early derivative uropodines have a variety of plates and often a thick covering of highly ornamented cerotegument (e.g. the long mite with the tail in the plate and the mite in the viewer’s upper righthand corner).  The more derived lineages, however, use shiny armour for defence and sometimes add detritus to the mix, e.g. the yellow Basket Mites (probably species of Clausiadinychus) in the lower left (ventral view) and upper right region (lateral view).  These mites have a basket formed of raised setae into which they deposit little balls of detritus.  Most higher uropodines, however, look more like turtles than baskets, and are sometimes called Tortoise Mites (not to be confused with the mites that are parasitic on tortoises or other turtles).

 The Uropodina is a massive radiation of mesostigmatans (Acari: Parasitiformes: Mesostigmata) that is most diverse in species and ecological associations in the southern lands that once composed Gondwana.  The elf hat mite is one that I have already posted on.  Mostly what these mites do is a mystery.  For example, I commonly get sent samples of Uroactinia agitans (probably better known as Fuscouropoda agitans) from people with earthworm colonies where these mites can build up tremendous populations.  As far as I know, these mites do no direct damage to the worms, although they may feed on dead or dying worms and possibly compete for resources.  But that is as far as I know – and a search on BIOSIS this morning failed to find any recent studies that support this relatively benign interpretation (the paper I read was from 1953).  So, if a no one is sure what a common synanthrope does, what we know about most Gondwanan species is probably minimal.

 One partial exception are the uropodine mites associated with doryline and ecitonine army ants in the Neotropics.  The diversity and extent of these associations was first documented by the late Carl Rettenmeyer (see Myrmecos Blog for a thoughtful review of his influence on ant people) during his PhD studies.  Since then, Richard Elzinga (see list of papers below) has described many of these fascinating myrmecophiles (under a variety of family and generic names now mostly treated as subgenera of Trichocylliba).  Unlike most higher uropodines, these mites attach to the ants as adults, rather than deutonymphs.  Some just hold on tightly with well developed claws to the mandibles, head or body of the ant.  Others, though, have bizarre modifications to facilitate attachment to specific spots on their ant hosts.  Some have toothed lobes of the body that clasp an ant leg segment or have the entire body modified to fit a leg or antennal segment.  Elongate mites of one genus (Habeogula) clamp the ant’s neck and align themselves under the labial region of the host’s head, presumably to steal food.

This is just a taste of the mesostigmatan associates of ants which include groups outside the Uropodina and such strange forms as the Larvamimidae, which look like army ant larvae and are treated as such by the ants, including lugging them around (Elzinga 1993).  Other mites are known to be kleptoparasites, e.g. Antennophorus grandis on the ant Lasius flavus (Franks et al. 1991).  True ectoparasitism has been demonstrated for one uropodine mite, Macrodinychus sellnicki (Dinychidae), which slowly suck the pupae of the Neotropical ant, Paratrechina fulva into shriveled little husks (Krantz et al. 2007).  A partial list of references follows.

Elzinga, R. J. 1978. Holdfast mechanisms in certain uropodine mites (Acarina: Uropodina). Ann. Entomol. Soc. Amer. 71: 896–900.

Elzinga, R. J. 1982. The generic status and six new species of Trichocylliba (Acari: Uropodina). Acarologia 23:3–18.

Elzinga, R. J.1982. The genus Antennequesoma (Acari: Uropodina) and descriptions of four new species. Acarologia 23:319–25.

Elzinga, R. J. 1982. Th e genus Coxequesoma (Acari: Uropodina) and descriptions of four new species. Acarologia 23:215–24.

Elzinga, R. J. 1989. Habeogula cauda (Acari: Uropodina), new genus and species of mite from the army ant Labidus praedator (F. Smith). Acarologia 30:341–44.

Elzinga, R. J. 1991. Two new elongate species of Planodiscus (Acari: Uropodina) with a key to the known species. Acarologia 32:109–14.

Elzinga, R. J. 1993. Larvamimidae, a new family of mites (Acari: Dermanyssoidea) associated with army ants. Acarologia 34:95–103.

Elzinga, R. J. & C. W. Rettenmeyer. 1970. Five new species of Planodiscus (Acarina: Uropodina). Acarologia 12:59–70.

Elzinga, R. J. 1974. Seven new species of Circocylliba (Acarina: Uropodina). Acarologia 16:595–611.

Franks, N. R., K. J. Healy, & L. Byrom. 1991. Studies on the relationship between the ant ectoparasite Antennophorus grandis (Acarina: Antennophoridae) and its host Lasius flavus (Hymenoptera: Formicidae). J. Zool. Lond. 225:59–70.

Gotwald, W.H. Jr.  1996.  Mites That Live with Army Ants: A Natural History of Some Myrmecophilous Hitch-Hikers, Browsers, and Parasites. Journal of the Kansas Entomological Society, Vol. 69, No. 4, Supplement: Special Publication Number 2: Proceedings of the Eickwort Memorial Symposium (Oct., 1996), pp. 232-237.

Krantz, G. W., L. A. Gomez, and V. E. Gonzalez. 2007. Parasitism in the Uropodina: A case history from Colombia. In Morales-Malacara et al., 29–38. Acarology XI, Proceedings, XI International Congress of Acarology. Mérida, Universidad Nacional Autónoma de México.

Rettenmeyer, C. W. 1961. Arthropods associated with Neotropical army ants with a review of the behavior of these mites (Arthropoda: Formicidae: Dorylinae). Ph.D. diss., Univ. Kansas.

Rettenmeyer, C. W.  1962. Notes on host specifi city and behavior of mymecophilous macrochelid mites. J. Kans. Entomol. Soc. 35:358–60.

Two, four, no, ten pests in one!

May 15, 2009
Nine Broad Mites hitch a ride on a whitefly
Nine Broad Mites hitch a ride on a whitefly

I guess I’m getting giddy from too much time humped over a computer or a microscope and a lack of sun and warmth (it’s a cold, late spring here in Alberta).  So here is something from a sunnier clime, or rather somethings.  The Bemisia whitefly in this image was sent to me by some colleagues in Toowoomba, Queensland (currently with a clear 8C autumn night and a weekend with predicted highs of 23 C, beating the May Long Weekend in Edmonton by 4-5 degrees).  Unfortunately, the whitefly was not covered with parasites, but with the infamous Broad Mite Polyphagotarsonemus latus (Banks) (Prostigmata: Tarsonemidae), a plant pest with, as you might guess from the generic name, a broad host range.  However, I think the common name comes from it being rather tubby (0.17 x 0.10 mm).

 Like many mites, the life history of the Broad Mite is amazing.  For one thing, they have reduced their life cycle to the almost the bare minimum – egg, larva, adult – cutting out all three nymphal stages.  At a constant temperature of 27 C, this mite can go through a complete generation, egg to egg, in 3 days and summer generation times in the field are typically 4-5 days.  As the larvae and adults feed, they distort leaf tissue into folds and bumps that protects them from weather and predators – not quite as fancy as the gall mites in the Eriophyoidea, but on their way there.

 Male Broad Mites have a large sucker-like genital capsule sticking out their rear end and they use this to hold onto inactive larvae – pharate females that are finishing up their development within the larval skin.  This looks a bit strange – the pharate female crosses the male T – and has fooled several entomologists into thinking they were observing an act of predation.  Nope, just males that want to make sure they alone go on a female’s first date.  This type of precopulatory guarding has evolved numerous times within the Acari, and in this case is associated with a male aedeagus and a female secondary sperm transfer system.  This makes quite a contrast to the oribatid mites with which I am currently working.  Male oribatids wander around depositing spermatophores on the substrate wherever they feel like it, whether or not females are around, and make no effort to contact, let alone guard, a female.  Perhaps that is one reason that 10% of oribatid mite species appear to be thelytokous (i.e. all female and parthenogenetic).

 As you may know, whiteflies are rather small, but not so small that a heap of broad mites can’t hitch a ride.  Mites lack wings, so if they want to get between patchy habitats, they have to come up with an alternative means of transportation.  A surprising number, including many members of the Broad Mite’s family (Tarsonemidae), simply orient to a stiff breeze and let go to become part of the aerial plankton.  That seems pretty inefficient if you have a specific place you’d really like to get before you dehydrate or starve, but I don’t know that climbing on such a tiny and seemingly inefficient flier as a whitefly is much better.

Getting Between a Gecko’s Toes

May 10, 2009
Geckobia bataviensis Vitzthum, 1926 - arrow points to gecko skin

Geckobia bataviensis Vitzthum, 1926 - arrow points to gecko skin

I suppose I could have called this post ‘a gecko’s nightmare’ and left out the question mark, but people often assume the worst about ‘parasites’. Certainly, this small, red Pterygosomatidae lives between the toes of the Asian House Gecko (Hemidactylus frenatus), pierces its skin, and feeds on the lizard (note hunk of skin wrenched off with the mite). Since the gecko needs its toes to keep a firm purchase on the walls of buildings, you would think a discerning parasite would find another spot, one less likely to result in a too slow dash away from a gecko-eater or in a long fall.  Gecko mites don’t seem to care, though.

The Asian House Gecko might appreciates the fact their mites, unlike other mites on the ‘native’ Australian gecko Heteronotia binoei, do not attach around their eyeballs.  Again you might think that having bulbous red skin-suckers dangling from your eyeballs might lead to a less alert lizard more likely to end up in something else’s stomach along with its mites, but I guess for a gecko mite, finding thin skin that it can pierce is more important than any existential angst.

Unlike most vertebrates, but like many mites, Heteronotia binoei is parthenogenetic.  Craig Moritz and his group have some interesting research on the ongoing and past evolution of geckos and their mites.  My student Anna Donahoo’s and my project on Geckobia bataviensis, however, was an attempt to be proactive about a potential future evolutionary interaction.  Pterygosomatid mites are known to vector blood parasites among lizards and we wondered if the introduced and spreading Asian House Gecko was a threat to Australia’s gecko diversity.  We found no evidence that the mites had crossed to ‘native’ geckos in the Brisbane region, and the local geckos have their own fearsome looking mites. So, so far, no worries.

Although introduced fairly recently to the Brisbane region, and successfully spreading only even more recently, the Asian House Gecko seems to have taken off and likely will become a permanent feature of Australia’s gecko diversity.  I can’t say that I minded that much – my house was infested with them and they were welcome to stay (and the cats welcomed them even more than I).  Sitting on the balcony in the evening and listening to the ‘chuck, chuck, chuck’ call of the male, is one of the things I miss in lizardless Edmonton.  Actually, we aren’t personally lizardless, because we inherited a leopard gecko from a graduate student who left town.  The leopard gecko is attractive, but like most geckos, silent.  We’ve been feeding him crickets and fortunately he is a clumsy and inefficient hunter, so we have a nightly serenade from the crickets that breed fairly well in the terrarium in our living room.  I wonder if there are any mites in there?

A Mycorrhiza’s Nightmare?

May 6, 2009
The business end of a proturan
The business end of a proturan

Gunnar wanted to see some different kinds of microarthropods, so here is one that is too little seen – the front end of an acerentomid proturan.  Proturans seem to be fairly common in forest soils in many parts of the world (this one is from Queensland), but I have yet to see one in Alberta.  Of course, 10,000 years ago Alberta was buried under a kilometer of ice, so they may be on their way, but yet to arrive.

 According to The Insects of Australia, proturans “are said to feed on mycorrhizal fungi”, but if I remember the paper this is probably based on, it was more correlation than actual observation.  It seems strange that the feeding behaviour of an entire Class of Arthropoda remains unclear, but last I heard what the Pauropoda eat was unknown too.  I should add that I tried several times to obtain feeding observations on both groups and all I got was deceased animals (and probably bad karma).

 Proturans are blind: the eye-like structure on the head is a pseudoculus and is thought to have ‘olfactory or chemosensory’ (Insects of Australia) functions, but a similar appearing organ in pauropods is thought to sense vibrations.  There are a number of published studies of the ultrastructure of the organ in both groups, but alas, the journals are not available at my library.  Unfortunately, this is often true for publications on the biology and morphology of soil microarthropods.

An intricate little blob

May 5, 2009
Not all blobs are featureless

Not all blobs are featureless

Although this blog is about mites, I’m interested in anything that is small and often ignored.  Springtails in the family Neelidae fit those criteria well.  I certainly ignored many thousands in my early work, because I didn’t realize the tiny white blobs in the sample were animals.  Once I’d realized that some of the blobs had legs, I became interested.  Steve Hopkin has an excellent illustration of just how small these animals are.

This is an Australian Megalothorax (most of the microarthropods you will see here were from Queensland) and I’m not sure of the species, but it is no bigger than the one that Steve Hopkin shows.  I don’t know the function of the concave depressions on the body, but I do wonder.  I can’t recall anything similar in mites.

Elf hat lost in the rainforest?

May 5, 2009
Uropodid mite or Elf hat?

Uropodid mite or Elf hat?

Last week I was reading one of Alex Wild’s post at Photo Synthesis about Anthropomorphism in Science Photography and trying to think how to make one of my mite images less alien and more appealing.  The best I could do was polish up this Queensland rainforest uropodid mite that always looked to me like a hat that  fell off the head of some elf scampering through.

The question of anthropomorphism in science is an important one, but complex.  When I first started colouring my SEMs 20-odd years ago, I asked one of my graduate students (who was also a good artist) what he thought.  He was aghast and thought me very unscientific.  For him, the grayscale SEM was the real representation of the animal and trying to colour it as it had been in life tantamount to massaging the data.  This reminded me of a tradition in some acarological line drawings where they would draw what they saw – if the mite had a big crack up the middle, so did the drawing.

I see things differently.  Mites do show colour and are not black and white.  Also, any SEM is a highly abstract image composed from the backscatter from the electron beam – a meld of information from whatever depths the electrons penetrate (as I understand it, usually on a micron or so).  Any and all pictures are abstracted from reality to one degree or another.  If your purpose is to use an illustration to demonstrate a scientific point, then your image can be scientific (assuming you aren’t fabricating the point).  If to make a political statement, then it is politics, and so on.  In this case, I think whimsy got the better of me.

In the Northern Hemisphere, uropodid mites (Mesostigmata: Uropodoidea)  are found primarily in discrete habitats such as compost, treeholes, bark beetle galleries, and ant nests.  They usually disperse as deutonymphs attached to insects by an anal pedicel (and look much like tiny lollipops).  In the Southern Hemisphere, uropodids occupy patchy habitats, but they also are one of the dominant members of the forest litter community.

A mite that glitters

May 1, 2009
A minute tongue-twisting brachychthoniid mite

A minute tongue-twisting brachychthoniid mite

Just how small can a terrestrial arthropod get and still function?  I’ve read a few theoretical discussions on how large an arthropod can get, but not on how small.  This golden wonder is towards the small end of the mite size spectrum, at least for adult mites.  The bar at the bottom is a tenth of a millimetre and this adult is not much longer.  An even smaller egg, larva, protonymph, deutonymph, and tritonymph preceded it, however.  The record for the shortest known adult mite is about 0.08 mm (80 microns) and belongs to an eriophyoid mite – tiny worm-like mites that form galls, rust, and silvering on plants.

In life, this mite was a transluscent golden colour.  I couldn’t quite capture that vivid living hue, but settled for the idea of what it might look like if an Inca goldsmith was trying to capture the essensce.  Other brachychthoniids (a real tongue-twister and often misspelled – Greek: brachy for short, chthon for soil) are a bright orange as adults (e.g.Eobrachychthonius latior) and violet as immatures.