There are no Big Mites and the Big Prawn is in Limbo

April 20, 2013
The Big Prawn in happier days

The Big Prawn in happier days

It is a sad truth that there is no Big Mite in Australia, nor indeed anywhere in the World so far as I know. There is a Big Ant, at least as an abstraction, in Broken Hill and a Big Mozzie in Hexham and even a not-so-itzy Big Spider in Urana. But no Big Mite. Once, though, Ballina could boast of a Big Prawn.

The Big Prawn today - just a shell

The Big Prawn today – just a pallid shell

Alas, the Australian sun sent the Big Prawn  to a barbie and it came out looking much like a 60 tonne white elephant. Then its raison d’être  closed and the 20-something Prawn was condemned to demolition by the Ballina Shire Council in 2009. Thanks to the reluctance of its owner, popular demand and a promise to refurbish by Bunnings Warehouse the shell lingers on in a vacant lot awaiting its resurrection. I hope Bunnings comes through with its promise. The Big Prawn was always my favourite stop on the north coast of New South Wales and the opening slide to my lecture on eating arthropods. I suppose I’m suffering from nostalgia, and certainly from homesickness in several ways, but I prefer a giant pink prawn to any number of giant pink squid.

Giant Squid on top of Questicon, Canberra

Giant Squid on top of Questacon, Canberra

Well, actually, I prefer calamari to prawns when it comes to eating invertebrates, but Paul Hogan never said he’d ‘throw another prawn on the barbie’ anyway.

The Big Prawn, in no way a shrimp

The Big Prawn, in no way a shrimp

Sea Spiders, Hexapods, and Great Appendages

December 21, 2012
Sea Spider larval stage (Stage 2?)

Sea Spider larval stage (3rd instar protonymphon)

The pycnogonids or Sea Spiders (Euarthropoda?: Euchelicerata?: Pycnogonida) are some of the strangest animals on the planet. All in all, pycnogonids are very peculiar: they have a proboscis, a 4-eyed turret, a special pair of limbs (ovigers) for holding young, a nauplius-like stage (protonymphon), the addition of limb-bearing segments during development  (anamorphosis), no abdomen to speak of (organs are displaced into the legs), and often too many pairs of legs. The front pair of pincer-like limbs has even been interpreted as possibly homologous with the ‘great appendages’ borne by ancient arthropods (Maxmen et al. 2005). Although the chelifores are now accepted as being the limbs of the same segment that produces the chelicerae, sea spiders remain difficult to relate to other arthropods (Brennis et al. 2008, Giribet & Edgecomb 2012). Strange or not, sea spiders seem to have been scuttling across the floors of silent seas since the Cambrian and apparently have never felt the urge to clamber onto land.

At one time, though, sea spiders were thought to be related to mites, mostly because mites also were considered strange and not related closely to anything else, but also because both have a more or less hexapod larval stage (Dunlop & Arango 2005). Fürstenberg (1861) even included pycnogonids as a family of water mites in his book with the scratch-inducing title “The itch mites of men and animals”. A larval pycnogonid (3rd instar protonymphon – see Bain 2003) is shown above. It does seem to be more or less hexapod (the hind pair of legs are sack-like and may be used for storing yolk) and to have what sort-of looks like a capitulum with palps and chelicerae (and a strand of silk) above the proboscis.

Oribatid mite larva - chelicerae, palps & 3 pairs of legs

Oribatid mite larva – chelicerae, palps & 3 pairs of legs

Mite larvae have a capitulum (= gnathosoma: composed of chelicerae and fused pedipalps) and three pairs of legs. The chelicera-like pincers  (chelifores) at the front-end of the pycnogonid protonymphon each has a palp-like structure at its base, and this does contribute to a resemblance to a larval mite, but in this case the “palp” is a “spinning spine” and silk is produced from a pore at its tip. Many acariform mites (Acariformes) are capable of producing silk (and spider mites do so from a pore on their palp), but my guess would be that the spinning spine is derived from the endite of the chelifore coxa. The next two appendages transform into palps and ovigers during development (Bain 2003) and it is only the sack-like blobs at the rear (bud-like in earlier protonymphon instars) that become the first of the walking legs. Legs IV develop first as buds in the embryo of acariform mites (Barnett & Thomas 2012), and in prelarvae and larvae in parasitiform mites, but limb buds are natural precursors for limbs.

Spherochthonius - a splendid little mite

Spherochthonius – a splendid little mite

So, I guess there really isn’t much similarity between the pycnogonid and the acariform mite larva, but it is interesting that basal acariform mites have a division of their bodies between legs II-III. This front end or proterosoma is possibly equivalent to the hypothesis of a ‘head’ (cephalosoma) of 4 limb-bearing segments in basal arthropods including pycnogonids. The gene regulation of the development of the rear end of mites is still poorly understood (Barnett & Thomas 2012), but something strange is going on and some surprises may await.

References

Barnett AA & Thomas RH. 2012. The delineation of the fourth walking leg segment is temporally linked to posterior segmentation in the mite Archegozetes longisetosus (Acari: Oribatida, Trhypochthoniidae). Evolution & Development 14, 383–392. DOI: 10.1111/j.1525-142X.2012.00556.x

Bain BA. 2003. Larval types and a summary of postembryonic development within the pycnogonids. Invertebrate Reproduction & Development 43, 193-222.

Bogomolova EV. 2007. Larvae of Three Sea Spider Species of the Genus Nymphon (Arthropoda: Pycnogonida) from the White Sea. Russian Journal of Marine Biology 33, 145–160.

Brennis G, Ungerer P & Scholtz G. 2008. The chelifores of sea spiders (Arthropoda, Pycnogonida) are the appendages of the deutocerebral segment. Evolution & Development 10:6, 717–724

Dunlop JA & Arango CP. 2005. Pycnogonid affinities: a review. J. Zool. Syst. Evol. Res. 43(1), 8–21  doi: 10.1111/j.1439-0469.2004.00284.x

Fürstenberg MHF. 1861. Die Krätzmilben der Menschen und Thiere. Leipzig: Wilhelm Engelmann.

Giribet G & Edgecomb G. 2012. Reevaluating the Arthropod Tree of Life. Annual Review of Entomology 57: 167-186.

Maxmen A, Browne WE, Martindale MQ, Giribet G. 2005. Neuroanatomy of sea spiders implies an appendicular origin of the protocerebral segment. Nature 437, 1144–1148.

Out of the box: A can of lice, good lice, naked middle thirds, and the hideous truth

October 19, 2012

Phthiracarus borealis (Trägårdh, 1910) = Louse + Mite + of the North

I’ve recently been looking at a bunch of ‘bug blogs’ and trying to assess them so I could make a statement about the health of bugbloggery for an upcoming symposium. One of the things that has struck me so far is that, although at the start the spirit may have been willing, the current blog is often weak. Many of the once interesting bug blogs that I have found seem to have run out of steam. If they haven’t posted in more than a year, I’ve been calling them ‘moribund’, but then I realised that here I haven’t posted since July. A quarter moribund? Well, I often feel even worse then that, so I guess I can’t complain if I am being quarter-hoisted by my own petard.

Mesotritia nuda (Berlese, 1887) = Middle + third + naked

So, here’s a mini-post, mostly just to keep from sliding into moribunditry, but also to try and work out one of those arcane problems that keeps me up at night – devising common names for obscure mites that no one has ever seen. In terms of existential angst, this must surely rank among the more absurd, but it is part of my job. I could just shoot from the hip, but I take even the more absurd aspects of my job seriously. I’ve blogged about this problem in other posts, but it hasn’t gone away, so here’s a current example: Box Mites. Being a ‘box mite’ is more a grade of evolution than a taxon – the ability to pull the legs into the body and shut the box has obvious advantages when a predator is trying to grab you by the leg and has evolved several times. The mechanism has been studied in some fascinating papers (e.g. Sanders & Norton 2004), but the authors have wisely never gone beyond the generic ‘box mite’. Unfortunately, Box Mites have done very well over the eons they have been around and acarologists have been giving them lots of obscure Greek and Latin derivative names for almost as long.

Atropacarus striculus (CL Koch, 1835)  – I hesitate to say what this may mean

Unfortunately, my scheme to use the Latin binomials as the source of my ‘common names’ has acquired an itch: the most diverse group of box mites belong to two superfamilies with names from the Greek for ‘lice’ (phthir) and ‘mite’ (acar), the Phthiracaroidea and Euphthiracaroidea, or ‘Louse Mites’ and ‘Good Louse Mites’.  There are mites that live like lice in the hairs and feathers of their hosts, but these aren’t them. The juveniles of box mites burrow in decaying plant material and the adults wander around the soil looking for each other and more decaying leaves and needles into which to lay their eggs. I don’t know what Perty was thinking in 1841 when he erected the genus Phthiracarus, but perhaps he was feeling itchy. Well, lousy name or not, even these mites have also been subjected to interesting studies of the box-making mechanism (e.g. Schmelzle et al. 2010) without wandering past the ‘box mite’ meme. So, I think I will draw my line in the sand at ‘box mite’ and try to summon forth names from the genus or species with which to adorn the box. So far, though, I must say I’m not having much luck. Take Atropacarus striculus as an example. I can’t find any root for ‘striculus’, but perhaps it refers to a stricture. I suppose the area where the legs are withdrawn may look strictured. Unfortunately, all box mites have a similar ‘stricture’. The generic name is also obscure. Perhaps from the Latin for hideous, terrible or cruel (atro-), but then why the extra ‘p’ before acarus? It’s times like these that I’m just glad I can still afford decent Australian wine. I think it is time I sought some inspiration there.

Faculifer sp. – a mite that infests the feathers of Australian doves

Moving to and fro on leaves: Phytoseiidae

July 20, 2012

Phytoseius oreillyi – Peter O’Reilly’s Leaf Rover

There are good mites, and bad mites, and many that are indifferent, but not many mites that are our friends. The Phytoseiidae (Acari: Mesostigmata), however, are our friends. This is because we share a common interest: spider mites (many of which are really bad mites). The species pictured above belongs to the type genus of the family: ‘Phyto’ (Greek for plant) and ‘seius’ (Greek for one who moves to and fro, or  shakes). The generic name perfectly captures the Gestalt of the family: they are mites that scurry across leaves looking for other mites to eat. This species was named for (Big) Peter O’Reilly of OReilly’s Guesthouse in Lamington National Park, Queensland. Although Peter preferred birds, he was always supportive of scientific research, even on mites. This species lives on the leaves of rainforest trees in the canopy of Lamington National Park. Peter seemed delighted that I named the mite for him, but Peter was never less than polite, so he may have been humouring me.

Man’s best mite friend: Phytoseiulus persimilis

O’Reilly’s Leaf-Roamer may or may not be of help to us in our long war with spider mites, but its cousin the Chilean Predatory Mites (Phytoseius persimilis) certainly is. The common name may or may not be accurate. The species was first described from the Mediterranean Region by the great Belgian-French acarologist Claire Athias-Henriot, but it was a cosmopolitan synathrope long before it was described. Our agricultural systems are very favourable to spider mite outbreaks. Phytoseiulus persimilis is a specialist predator  of spider mites, especially those that produce dense webs of silk such as the Two-spotted Spider Mite (Tetranychus urticae), a very bad mite. Although it tends to follow us around, good biological control requires using your predators at the appropriate time in the prey’s population cycle. Fortunately, nowadays you can buy boxes of Chilean Predatory Mites to sprinkle on your greenhouse crops, strawberries, and other crops to fend off damage by spider mites.

Amblyseius sp. – a genus with many good mites

A triple tribute to Funk: Funkotriplogynium iagobadius

July 7, 2012

Juvenile antennophorine mite

For no particular reason, other than it being a really good mite, I offer a view of a very dead juvenile collected in association with the infamous Funkotriplogynium iagobadius Seeman & Walter, 1997. Mites in the Antennophorina (Mesostigmata) are best known as associates of large arthropods, especially beetles and millipedes, but some live with ants, bees and termites, and others with cockroaches and earwigs living in stable habitats such as under rocks and in logs. For example, Paradiplogynium nahmani Seeman, 2007, was described from Australia’s Colossus Earwig Titanolabis colossea (Dohrn 1864) – at about 6 cm long, one of the World’s largest Dermaptera. Antennophorine mites are no slouches when it comes to size either. Adult Diplogyniidae, the earwig mite’s family, usually approach a millimetre in length and some of the Megisthanus on passalid beetles reach 5-6 mm in body length, as large as some ticks. Diplogynium Canestrini, 1888, type genus of Diplogyniidae Trägårdh, 1941, is but one of forty-odd genera and almost 100 described species in that family , and although the largest family of Antennophorina, is but one among 21 families grouped in 7 superfamilies.

Mop-like cheliceral excrescences of Micromegistus – an associate of carabid beetles

In spite of these mites being relatively large and living on often well-studied arthropods, little is know of their life history. The ant associates in Antennophorus make their living by making ants regurgitate food (sounds disgusting, but it’s a life). But for others it isn’t clear: the adults hang out on their hosts doing something with their mouthparts from which large mop-like excrescences dangle. What they are doing, however, is a mystery. Some authors have hypothesized that they feed on the ‘dermal secretions’ of their hosts. The larvae and nymphs are usually not found on the arthropods, so they are almost completely unknown, but some have been found wandering in galleries and have been thought to ‘scavenge’ or feed on fungi, the usual default guesses for  ‘I don’t know’.

Mysterious mouthparts of Megisthanus – an associate of passalid beetles

Fortunately, not all Antennophorina are inveterately found on large arthropods: a few are more or less free-living. One such group is the rather plesiotypic family Triplogyniidae, based on the then new genus and species Triplogynium krantzi Funk, 1977, from Central Africa. In 1985 AK Datta described a second genus in the family and added Dick Funk’s name to create the rather earthy, but not at all syncopated, name Funkotriplogynium. This latter genus also occurs in Australia and a student, Owen Seeman, and I were able to both observe feeding by the adults and describe the juveniles. This gave us an indication that predation was the basal mode of feeding in Antennophorina and gave Owen the opportunity to win fame and infamy with his species name. Owen has a lot of things to answer for (my having to feed chickens the first thing in the morning immediately comes to mind), but he has earned his spurs as an acarologist by almost singlehandedly exposing the mysteries of antennophorine development and ecology. Although much remains to be explained, including the function of those fabulous excrescences, it seems clear now that taking a bite out of whatever arthropods or worms are encountered while wandering in the galleries and nests of their hosts is the first thing on the minds of many antennophorines.

These teeth were made for biting and that’s just what they do

References:

Datta AK. 1985. A new genus and species of the family Triplogyniidae (Acari: Mesostigmata) from Assam, India. Indian Journal of Acarology 9: 48-56.

Funk RC. 1977. Triplogynium krantzi n.g., n. sp., type of Triplogyniidae (Mesosligmata: Celaenopsoidea). International Journal of Acarology 3: 71-79.

Seeman OD & Walter DE. 1997. A new species of Triplogyniidae (Mesostigmata: Celaenopsoidea) from Australian rainforests. International Journal of Acarology 23: 49-59.

Seeman OD. 2000. The immature stages of the Fedrizziidae (Mesostigmata: Fedrizzoidea). Acarologia 41: 39-52.

Seeman OD. 2007. A new species of Paradiplogynium (Acari: Diplogyniidae) from Titanolabis colossea (Dohrn) (Dermaptera: Anisolabididae), Australia’s largest earwig. Zootaxa 1386: 31-38.

Seeman O.D. 2012  Larva and deutonymph of Promegistus armstrongi Womersley (Acari: Mesostigmata: Trigynaspida: Promegistidae). Memoirs of the Queensland Museum – Nature 56(1): 255-269.

Electron-raster Challenge III: Name this mite

June 28, 2012

Name the family and, for extra fame and fortune, the suppressed seta.

Anyone can play, but this Challenge is posted especially for the students in Acarology Summer Program Soil Acarology course. At least one semi-bingo character is readily visible. The mite is from Alberta, and most prominent in northern forests, but not above an alpine vacation in Mexico. Why swelter in the 100 F Columbus heat, when you can ponder this boreal beasty in over-airconditioned discomfort at your own computer screen.

Electron-raster Challenge II: Name this mite

June 16, 2012

A species name may be a nomen nudum, maybe not, but again genus is probably possible to guess and suborder certainly is

Posting at macromite isn’t what you might call a regular occurrence, but all work and no play makes for a dull life. So here, in quick succession, are the bug blogger’s first choice when time and energy lag: an identification challenge. In this case both are cropped and both are mites. After that you are on your own.

Electron-raster Challenge: Mystery mite

June 16, 2012

Mystery mite

Don’t try for species, that would be a nomen nudum, but genus is doable

How small are mites: the Full Stop Test

May 19, 2012

8 Oribatid mites scaled to a 12 pt Times Roman period (0.5 mm dia.)

Recently The BugGeek posed an interesting challenge: “Can you talk to 10-year-olds about science?” I found this especially interesting because, as an acarologist, I find it difficult to explain the study of non-pest mites to people of any age or educational level. Usually when asked my occupation, I just say ‘I’m a scientist’ or, if among university types, ‘a biologist’ or ‘I work on bugs’. Other than with voluble taxi drivers, this usually proves satisfactory. Sometimes (usually under the influence of alcohol) I do try to explain to strangers the excitement I feel about the diversity of intricate morphologies and amazing behaviours exhibited by mites. But in my experience, if you have a party that has been going on for too long, then I am just the person you need to send even the most couch-bound inebriate scratchingly on their way.

A few years ago, though, I was asked to try and explain mites to 2nd Graders. I decided that the critical information was size – if I could explain how small mites were to an 8 year old, then I’d have a chance. I played around with a how many mites would your foot-print cover (a number too large even for a government deficit) and a penny, but even a penny can hold about 7000 of the smallest mite in the picture above and even in a large poster the mites are too small to see. I finally settle on a Times Roman 12 pt period, conveniently 0.5 mm in diameter. Times Roman and similar serif fonts are those most commonly used in publications (the little feet make a sort of dotted line for the eye to follow while reading) and every sentence ends in a full stop. What could go wrong?

Well, the good news is the 2nd Graders liked the pictures of the mites. The bad news is that ‘period’ does not compute in the 8-year-old mind. We tried inverting the background so that the period was black and the background white (which involved several hours of cleaning up black speckles), but ‘what’s a period?’ proved too great a hurdle. Oh well, it still makes a nice poster.

 

On Mites, Roofs & Jargon: Tectoribates

April 6, 2012

A Roofed Roamer from aspen litter under the January snow

The search for the origin of Oribatida has made some significant progress thanks to a number of classicists and oribatologists and after I’ve tracked down one last reference, all will be revealed. In the meanwhile, in a comment on the last post, James Trager pointed out that ” a better translation for Tectoribates would be either thatch roamer or roof roamer (roofs having once been mostly made of thatch)”.  This hypothesis is supported by the OED, which gives the origin of words like ‘tectiform’ (=roof-shaped) from the Latin ‘tectum’ (=roof). Additional support comes from Gordon Gordh’s and David Headrick’s excellent A Dictionary of Entomology (ADE, 2001 CABI), who point out that ‘tectiform’ is used to describe insects like cicadas that hold their wings roof-like in repose and also from Donald Borror’s handy Dictionary of Word Roots and Combining Forms (1971, Mayfield Publishing Company) that gives ‘tect-‘ as arising from the Latin and Greek for roof. This raises a number of problems though. First, my Tectoribates species are neither arboreal (so not roof mites) nor from grasslands (so thatch would be misleading), nor is any structural feature like thatch or a sloping roof. Second, acarologists have their own definition:  tectum (pl. tecta) – any shelf-like projection of the cuticle.

Acarologists often go their own way on terminology, and this is especially true of oribatologists. As a recently reconverted oribatologist (after a quarter century pursuing other types of mites), my pet peeve with the oribatid jargon is ‘sensillus (pl. sensilli)’ – used for the motion-detecting seta that emerges from a cup-like receptacle on the prodorsum (the spiky, club-like structures on the image above). All the rest of animal morphology uses the neuter form ‘sensillum (pl. sensilla)’ for a sensory seta or other sense organ. ‘Sensillus’ causes no end of confusion and snide comments when a literate, but non-oribatological, referee gets a paper. However, in defence of this non-conformity, it is worth noting that ADE gives ‘sensillum’ as being derived from the Latin ‘sensus’ (=sense), a masculine noun, and so the oribatologists may hold the high ground here.

On further study, this also seems true of ‘tectum’, or at least there is more too it than an A-shaped roof. Cassel’s Latin Dictionary (1968, Wiley) gives ‘tectum’ as the substantive of ‘tego’ the verb ‘to cover’ and exemplars of usage including burying, protection by a shield, and to conceal. The last two would seem to go to the heart of the tecta of oribatid mites: most such structures are designed to shield or cover the legs or other parts of the body where a nasty predator might try to gain a foothold. In the picture above you can see a variety of such tecta including the wing-like pteromorphs that cover the legs, the pedotecta at the base of the legs, the tutoria* (from the Latin to guard or protect) protecting the outer sides of legs I , and the median lamellae (from the Latin for a small plate) covering the tops of legs I. Nature must be very red in others’ teeth and claws for an oribatid mite.

Looking down on lamellae roofing the prodorsum

In Tectoribates the lamellae are unusually well developed and I suspect that Antonio Berlese may have been thinking ‘roof-like’ when he coined the genus in 1910. So, I’m going with Roofed Roamers and my thanks to James.

*tutorium, tutoria (not tutor as the spellchecker would have it)