Mite Harvestman: Austropurcellia inter alia

Details of the ventral cuticle of a mite harvestman Austropurcellia sp.

I should probably entitle this post as an homage to Robert Burns’ poem ‘To a Mouse’, because this ‘best-laid schemes o’ mites an’ men, Gang aft agley’ (tacky true, but irresistible) has been an orphaned draft for more than two years, but then 2013 was truly gang aft agley. In any case, I wanted to congratulate Boyer & Router on their 2012 paper* advancing the study of a fascinating group of little-known arachnids, the Cyphophthalmi.

Venter of a male pettalid, possibly a species of Austropurcelia, from Queensland. Scale bar = 1 mm

Interestingly, the openings to the tracheal system are positioned behind the legs and the genitalia (segment VIII) as one would expect, but the juveniles have a series of spiracle-like structures in the soft pleural region of the opisthosoma. These structures do not seem to connect to any tracheal or duct system, but presumably have some function.

 

Venter of Australian pettalid juvenile. Red arrow indicates one of the mystery organs.

 

What makes these structures particularly interesting is they seem to be similar to the mystery organ on adult Allothyrus (Acari: Holothyrida) mites called the peridium. I think it looks rather like the tool I used to use to clean sparkplugs, but I can’t think how the mites could insert anything in such an awkward position. Perhaps it is an organ for releasing pheromones or allomones, but I never found an obvious reservoir associated with the peridium.

Adult Allothyrus from Queensland showing peridium behind leg IV (and close-up). 

Well, hard to rule out convergence, but it is an interesting similarity between these small, mite-like opilionids and the rather large (for a mite) and ‘primitive’ Allothyridae.

 

Siro acaroides (Ewing, 1923) from Mary’s Peak, Oregon, USA – a mite-like Cyphophthalmi

 

*Sarah L. Boyer and Catherine N. Reuter.  2012. New species of Austropurcellia mite harvestmen (Opiliones, Cyphophthalmi, Pettalidae) from Australia’s Wet Tropics, with commentary on biogeography of the genus. In press, Journal of Arachnology. Journal of Arachnology 40.1: 96-112.

See also Giribet & Shear 2010 http://scholar.harvard.edu/files/ggs/files/giribet_shear_2010.pdf

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

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 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 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

Sea Spiders, Hexapods, and Great Appendages

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

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

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.

And the answer is …

Putative Mycetophagus prepupa with Paracarophenax

Well, Ted gets a point for the adult beetles – they are Mycetophagidae – and a species of Mycetophagus according to Arnett, although if the adult male beetle didn’t have a distinctive tarsal formula, I’m not sure I would have ever keyed it out. A coleopterist now has the specimens and a species identification may be forthcoming. The associated larva is not a Ciidae – I think these are restricted to polypore mushrooms and the habitat was a fleshy gilled mushroom, Pleurotus ostreatus.  My inference that the larvae associated with these adult beetles is the same species is based on co-occurance, appropriate size, and lack of any alternative. I’ll see if I can get a specialist to agree, but larvae don’t seem to be especially well known.

I think I’ll have to give Kaitlin the win here, though, with three points: one for recognising the mite as a member of the Heterostigmatina (aka Heterostigmata), one for a creative (if wrong) story about the life history, and one for boldly guessing where no other acarologist dared.

The mite is, in fact, an undescribed species of Paracarophenax Cross, 1965 (Acariformes: Heterostigmatina: Acarophenacidae). Of the five described species in the genus (Magowski 1994), Paracarophenax dermestidarum (Rack, 1959) seems to be the only species that has been studied in any detail – it is a parasitoid of the eggs of a dermestid beetle. However members of other genera in the family are of considerable interest as biocontrol agents of stored product beetles.

For example, Acarophenax lacunatus (Cross & Krantz, 1964) is an egg parasitoid of a number or grain-infesting beetles (Oliveira et al. 2003a,b) including the Lesser Grain Borer Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae). Adult female mites are phoretic on adult beetles. The mites detach from the beetle as eggs are laid. A mite attaches to the egg, swells up (physogastry), and as it kills the egg up to two dozen offspring develop inside the body of the mother mite (Faroni et al. 2000). One or two of these internal young are males and they mate their sisters before they pop open the mother and start looking for new eggs or new beetles to hitch rides on.

This seems to be the general life style of these mites, including those in the genus Adactylidium Cross, 1965 on thrips eggs and Aeithiophenax Mahunka, 1981 on the eggs of scolytine bark beetles. So, we may assume that our Paracarophenax does something similar. I’m not aware of reports of these mites attaching to larvae, but the three ‘Mycetophagus‘ larvae with mites were all large, plump, and probably prepupae (smaller larvae did not harbour mites). In the swampy morass of a decomposing oyster mushroom, I think it makes sense that the mites hang on (they were not feeding) to the late stage larva. One wonders where pupation takes place, but for the mites to have another generation, they need to hitch a ride on an appropriate insect.

Further reading:

Cross EA, Krantz, GW. (1964) Two new species of the genus Acarophenax Newstead and Duvall 1918
(Acarina:Pyemotidae). Acarologia, 6, 287-295.

Faroni LRD’A, Guedes RNC & Mathioli AL. (2000) Potential of Acarophenax lacunatus (Prostigmata:Acarophenacidae) as a biological control agent of Rhyzopertha dominica (Coleoptera: Bostrichidae). Journal of Stored Products Research, 36,  55-63.

Magowski WL. (1994) Discovery of the first representative of the mite subcohort Heterostigmata (Arachnidae:
Acari) in the Mesozoic Siberian amber. Acarologia, 35, 229±241.

Oliveira CRF, Faroni LRD’A, Guedes RNC. (2003a) Host egg preference by the parasitic mite Acarophenax lacunatus (Prostigmata: Acarophenacidae). Journal of Stored Products Research, 39, 571–575.

Oliveira CRF, Faroni LRD’A, Guedes RNC, Pallini A. (2003b) Parasitism by the mite Acarophenax lacunatus on beetle pests of stored products. BioControl, 48, 503–513.

Rack G. (1959.) Acarophenax dermestidarum sp.n. (Acarina, Pyemotidae), ein eiparasitic yon Dermestes arten. Z.  Parasitenkunde, 19, 411-431.

And the Answer is: Polyxenid Millipede

the presentable part of a polyxenid from Queensland

As Christopher Taylor deduced, the 3^rd Electron Challenge is none other than a member of the millipede subclass Penicillata and its only order Polyxenida. The cephalic trichobothria and disaggregated eye cups are characteristic of this group. Müller et al. (2007) consider the eyes to be secondarily reduced, miniaturized ommatidia and used their study of eye ultrastructure to argue both for the homology of all mandibulate eyes and a possible synapomorphy of the Myriapoda (millipedes, centipedes, symphylans, and pauropods).

Polyxenid in the courtyard: tiny, but not defenceless

Christopher also hypothesizes that parthenogenesis may help them to colonize extreme habitats like the Spanish Moss (the lichen-like bromeliad Tillandsia usneoides) that dangles from trees, especially live oaks, in the south eastern USA. Some populations of species of Polyxenus, at least, are parthenogenetic, so I suppose, that is a possibility under the General Purpose Genotype Hypothesis about the persistence of parthenogens. But, both bisexual and unisexual polyxenids are unusual among Diplopoda in that many inhabit xeric environments such as rock surfaces, bark, and even Spanish Moss (Whitaker & Ruckdeschel 2010). Wright & Westh (2006) recently demonstrated that Polyxenus lagurus (L.) is capable of absorbing atmospheric water vapour down to relative humidities of 85% – so far the only known millipede to have this ability. So, this ability seems more useful for climbing trees than the ability to do without males.

Our somewhat deformed specimen is from Queensland. Three families of Polyxenida have been recorded in Australia (Lophoproctidae Silvestri, 1897; Polyxenidae Lucas, 1840; Synxenidae Silvestri, 1923), but I don’t know which one this Queensland specimen represents. Unlike all other millipedes, polyxenids (this ‘common name’ could be confusing since it can be applied both to the family and order – but I’ll use it for the order) are soft-bodied and preserving them for SEM is tricky (also the setae, especially in the posterior pencil-like tuft, fall out and get stuck to everything else in the dish). Only about 160 polyxenid species are known today, but the group is very ancient with fossils in amber known from the late Cretaceous – and all have the whorls of serrate setae and the dense pencil-like tuft of fine setae on the rear.

Eisner et al. (1996) have a fascinating (and currently freely available) paper in the unfortunately acronymned PNAS that demonstrates that a North American species of Polyxenus uses the pencil tufts of modified setae on their posterior to thwart predation by ants. In fact, they use the ant’s mechanoreceptor setae and grooming behaviour as a death trap. When an ant approaches, the polyxenid swings its butt around and brushes the tuft of setae against the ant. Grappling hook-like processes on their tips (see the excellent SEMs in the paper)  snare setae on the ants mouthparts and legs and are shed as the millipede moves away. When the befouled ant attempts to clean itself the jagged-edged bristles become entangled and an elaborate snare begins to envelop the ant’s legs and mouthparts, often resulting in the eventual death of the ant (at least in the lab).

The whorls of setae on the body lack the grappling hook ends, but easily fall off and may provide a similar, last ditch defence against being grabbed by a predator and allow the polyxenid a chance to bring its death brush to bear. Polyxenid fossils are only known from the late Cretaceous and Polyxenus from the Eocene (Nguyen Duy-Jacquemin & Azar 2004), so this behaviour may have evolved in response to ants, but millipedes seem to have originated by at least the mid Ordovician and the Polydesmida are either the sister group to all other millipedes or, at the latest, originated in the Carboniferous (Wilson 2006), so this defence may be more than just a myrmicide. Also, not all ants let polyxenids entangle them.

Neotropical ants of the genus Thaumatomyrmex (they feign death when disturbed) hunt the polyxenids abundant in leaf litter (Brandão et al. 1991). A polyxenid is seized by the ant’s antennae, snapped by the wicked-looking mandibles, and then stung and carried back to the nest. In the nest the paralyzed polyxenid is turned belly up and stripped of its setae using the fore tarsi which have “small but stout setae” (perhaps too stout to be engaged by the grappling hooks) and the mandibles. This can take 20 minutes, interrupted by bouts of grooming, so it seems the polyxenid setae may still be fighting back. Brandão et al. thought the setae must have a noxious chemical – this being the normal millipede defence – but Eisner & Deyrup have shown that the morphology of the setae themselves can be fatal and no chemical defence need be invoked. The hunter then eats most of the polyxenid and feeds the remains to a larva.

Polyxenus Latreille, 1803, seems to have given its name to this strange and ancient group of millipedes, but I’m not sure where ‘Polyxenus’ (‘very or many strange’ or ‘very hospitable’ are two possible translations) comes from. Polyxena, the daughter of King Priam of Troy, who came to such a gruesome end on the pyre of Achilles, would seem to be one possible answer, but ‘Polyxenus’ is not feminine and the animal is not hospitable and anything but a willing victim. Polyxenidas was a renegade Rhodian admiral known mainly for treachery and losing naval battles to the Romans, but there is nothing marine or ship-like about these dry-adapted animals (although they may be found on beaches). I think it must be the many strange setae that inspired Latreille and that seems very fitting.

Short Bibliography

Brandão, C. R. F., Diniz, J. L. M. & Tomotake, E. M. (1991) Thaumatomyrmex strips millipedes for prey: a novel predatory behaviour in ants, and the first case of sympatry in the genus (Hymenoptera: Formicidae). Insectes Sociaux 38: 335-344.

Eisner, T., M. Eisner and M. Deyrup. 1996. Millipede defense: use of detachable bristles to entangle ants. Proceedings of the National Academy of Sciences 93: 10848–10851.

http://www.pnas.org/content/93/20/10848.full.pdf

Müller CHG, Sombke A & Rosenberg 2007. The fine structure of the eyes of some bristly millipedes (Penicillata, Diplopoda): Additional support for the homology of mandibulate ommatidia. J. Arthropod Structure & Development 36: 463-476

Nguyen Duy-Jacquemin M. & Azar D. 2004. — The oldest records of Polyxenida (Myriapoda, Diplopoda): new discoveries from the Cretaceous ambers of Lebanon and France. Geodiversitas 26 (4) : 631-641.

Nguyen Duy-Jacquemin, M., and J.-J. Geoffroy. 2003. A revised comprehensive checklist, relational database, and taxonomic system of reference for the bristly millipedes of the world (Diplopoda, Polyxenida). African Invertebrates. 44(1):89-101.

Whitaker JO Jr & Ruckdeschel C. 2010. Spanish Moss, the Unfinished Chigger Story. Southeastern Naturalist 9:85-94.

Wilson HM. 2006. Juliformian millipedes from the Lower Devonian of Euramerica: implications for the timing of millipede cladogenesis in the Paleozoic. J. Paleont. 80: 638–649

Wright JC & Westh P. 2006. Water vapour absorption in the penicillate millipede Polyxenus lagurus (Diplopoda: Penicillata: Polyxenida): microcalorimetric analysis of uptake kinetics. The Journal of Experimental Biology 209: 2486-2494.

A long and more normal millipede:

A more traditional Australian millipede

And the answer is: Austromesocypris

Looks like peteryeeles from ptygmatics takes honours for this 2nd Electron Raster Challenge, or at least I agree with the first half of his rather broad hypothesis: Austromesocypris. Also, Koen Martens took a break during his most recent field trip to Australia to view the image and agrees (but points out dissection would be needed to determine the species). If you want to learn more about these fascinating terrestrial ostracods, then I highly recommend the 2004 paper by Martens and his colleagues, a wonderful combination of taxonomy, phylogenetic analysis, and zoogeography:

Koen Martens, Patrick De Deckker, Giampaolo Rossetti. 2004. On a new terrestrial genus and species of Scottiinae (Crustacea, Ostracoda) from Australia, with a discussion on the phylogeny and the zoogeography of the subfamily. Zoologischer Anzeiger 243: 21–36.

As for the blobs that have everyone stumped, you will have to take my word for it – rotifers – or at least that is what a few that I slided from a companion Austromesocypris turned out to be. The preparation for SEM was not very kind to them, but I thought they would make a nice link to the first Challenge and its spiny-headed rotifer gone monster. During the rainy season the forest floor is as wet as my garden in this torrential Alberta summer, which is extremely wet, so the rotifers may be commensals taking advantage of a mobile feeding platform. However, since this ostracod crawled out of a sample drying on a Berlese funnel, perhaps rotifers also engage in phoresy.

I know I have a few more Greyscale images of Austromesocypris somewhere on a cd, but since I can’t find them, I’ll just have to end this post with a tiny mite first described by the great A.D. Michael 125 years ago:

A mite found wandering the Meanook Biological Research Station in Alberta

Inspired by Myrmecos: Parajapyx

Parajapyx - another long, lean, post-crustacean

This posting was inspired by Myrmecos, a general lack of inspiration, and just wondering what a 500 pixel wide microarthropod might look like. Although there are some long, lean mites that might be more appropriate, Prolixus forsteri comes to mind, or perhaps the unbeatable long lean acarine, Gordialycus tuzetae Coineau, Fize & Deboutteville 1967 – which looks more like a giant nematode than a worm (for a light micrograph see*), alas, I have no pictures of them.

Really, I’m just tired of shovelling snow (~20 cm today, and it is well into May) and ready to veg out in front of the most recent Circus of the Spineless, so here’s one of my larger contributions, a ~ 3 mm long Parajapyx species from Queensland (where snows are few and far between). Not much seems to be known about these mini-diplurans. The monstrous Heterojapyx (~ 20 mm) make better pets, especially if you enjoy watching them catching collembolans with their posterior pinchers, twisting around their abdomens, and then eating the RSPCAless springtails alive, but are far too large to contemplate for the SEM.

Heterojapyx sp. -one of the largest living dipluran

*Norton RA, Oliveira AR & de Moraes GJ. 2008. First brazilian records of the acariform mite genera Adelphacarus AND Gordialycus (Acari: Acariformes: Adelphacaridae and Nematalycidae) Internat. J. Acarol. 34: 91-94.

Seeing Red & Being Blue: Polymorphus

A carotenoid mite (UV protected) feasting on spider eggs

Waiting for an answer to a Macromite Electron Raster Challenge is a bit like waiting for a warn spring day in Edmonton: patience may be rewarded, eventually. But warmth is predicted for today (although along with a brisk wind) and I decided to take the day off work and catch up at home. First up is awarding points, or rather first up is fitting a mite into this somehow, and I offer a red Queensland Charletonia mite eating spider eggs while baby spiders look on in horror in honour of the Queenslander with the best answers. In the mite’s case, UV-protection and perhaps an advertisement of bad taste are thougth to be the reasons it is red.

 Without a doubt, Snail’s Eye View was there the firstest with the mostest (although Adrian should get some kind of prize for ketchup). So, congratulations to Bronwen Scott from the beautiful and diverse Atherton Tablelands where I used to spend many a happy day plucking mites from rainforest canopies.

 No one really knows why Polymorphus marilis sequesters carotenoids and no one got the species correct – hardly surprising since  the worm, a specialist on its definitive host the Lesser Scaup Aythya affinis (Bush & Holmes 1986), is nowhere near as well known as P. minutus, P. paradoxus, or a host of other carotenoid blazing acanthocephalans that adorn the pages of various scientific journals. Most cystacanths of Acanthocephala lack colour, but the more famous ones shine through their intermediate hosts’ cuticle as bright yellow-orange to red spots.

 Photoshop aside, one could claim that the reason these cystacanths are red is that they sequester carotenoids from their intermediate hosts, and this does seem to be true, but why? Well warning colouration and protection from ultraviolet light are two common uses of carotenoids, but neither makes sense here – the worms want to get eaten (at least by the definitive hosts) and one would think (perhaps incorrectly) that they are protected from UV under the cuticle of the amphipod intermediate host. So what is going on?

Mallard bum with amphipods & Amphipod with acanthocephalan

 Well, one definite effect of this red pigmentation has been to cause quite a few scientists to paint red spots on uninfected amphipods to see if they are more likely to be eaten by definitive hosts (usually ducks or fish) than unpainted amphipods. The results have been mixed (see Ted’s link and the Bakker et al. paper listed below for two contrasting fishy examples, and Bethel & Holmes and the citations therein for the fowl truth). Peter links to a paper that reports that European P. minutus appear to cause sterility in an another amphipod, and perhaps, the sequestering of carotenoids is related to failure to produce eggs. Zohar & Holmes (1998) also demonstrate that Polymorphus-infected Gammarus lacustris males are less likely to pair up or guard mates. But, more interesting associations between red acanthocephalans and their various hosts are changes in amphipod colour (loosing their camouflage brown) and behaviour (losing their fear of light so that they swim near the surface, tending to cling to anything they touch).

Gammarus lacustris with & without carotenoids in cuticle

 Amphipods that are not infected by an orange acanthocephalan maintain carotenoids in their cuticle, and thus, acquire UV protection, a brownish hue that blends in with lake bottoms, and the typical reddish shell of a boiled crustacean when they die. This is wonderfully illustrated by a concise and informative letter to Nature by Ole Hindsbo – again on P. minutus, but this time in New Zealand. In less than one page, Hindsbro elegantly demonstrates that most (but not all) infected Gammarus lacustris are pale because their blue blood shows through their carotenoids deficient cuticle, that the pale amphipods are more likely to swim in sunny spots where they would be easily seen by a definitive host, and that in the lab a duckling is more likely to eat the pale, infected amphipods. He also cites M. Denny’s PhD thesis (from UA no less) showing that Gammarus lacustris infected with Polymorphus paradoxus tend to cling to floating objects (see mallard picture). Dabbling ducks like a mallard may not be proficient at hunting arthropods in the water column, but Bethel & Holmes (1977) demonstrated that clinging to a mallard bum is a good way to get a mallard to eat amphipods infected with P. paradoxus. Scaup do hunt and consume a lot of amphipods, so one might hypothesize that those infested with P. marilis would be less likely to cling and more likely to paddle palely through the water column.

 So why are some acanthocephalans red? I vote for ‘because they make their hosts blue’.

 Thanks to all those students of red acanthocephalans who have provided me with so many hours of interesting reading. Special thanks to John Holmes for a sparking discussion on worms, ducks, and muskrats at the Strickland dinner and to Leo Balanean for many interesting stories about amphipods and their worms on those early morning bus rides and for the use of his picture. When Leo’s thesis is finished, the world will know just how red Polymorphus marilis and paradoxus really are.

 References (also see links in comments):

Bethel WM & Holmes JC. 1977. Increased vulnerability of amphipods to predation owing to altered behavior induced by larval acanthocephalans. Can. J. Zool. 55: 110-115.

 Bush AO & Holmes JC. 1986. Intestinal helminths of lesser scaup ducks: patterns of association. Can. J. Zool. 64: 132-141

 Bakker TCM, Mazzi D & ZalA S. 1997. Parasite-induced changes in behavior and color make Gammarus pulex more prone to fish predation. Ecology 78(5): 1098–1104.

 Hindsbo, O. 1972. Effects of Polymorphus (Acanthocephala) on colour and behaviour of Gammarus lacustris. Nature 238: 333.

Zohar S & Holmes JC. 1998. Pairing success of male Gammarus lacustris infected by two acanthocephalans: a comparative study. Behavioural Ecology 9: 206-211.

Macromite’s 1st Electron-Raster Challenge

What is it and why is it red?

A tradition on many blogs is to present a picture of a mystery organism for readers to identify. Some bloggers have even been known to use creative cropping to ensnare and mislead their readers. Given the obscurity of my organisms, though, it wouldn’t be much fun putting up a mystery mite – seems unlikely anyone but a specialist would be able to guess the answer. That would not be very sporting and I wonder if anyone would even bother to make a guess.

 In this case, however, I think the answer should be self-evident, so I’ll make this a bit more complicated. For 10 Macromite Points®*, name the organism and reason for its startling red colour. Here’s another hint – molecular characters support a surprising hypothesis of a relationship between the mystery and some very common organisms that are much more within my size comfort zone.

For 5 bonus points, name the pigment type used by the mystery above and the somewhat larger organism below for quite different purposes.

Mite habitat in a Sambucus racemosa sprucing up for a Spring fling

 *100 points are good for one free mite identification!

And now a plug for beetles

A tiny Australian beetle – probably Pselaphidae Eupinion (thanks Don)

I think this small staphylinoid beetle is a member of the Pselaphidae, or what used to be the Pselaphidae – now reduced to a subfamily of Staphylinidae by some authors. Perhaps some knowledgeable pselaphologist can tell me yea or nay (Don Chandler suggests Eupinion sp.). Supposedly there are about 85 species of Pselaphinae known from Canada and Alaska, but this particular one once lived in subtropical rainforest in southeast Queensland.

Pselaphid beetles are interesting to me for two reasons: they tend to be tiny and some eat mites (although more seem to enjoy eating springtails). Others find them interesting because they are ant inquilines and kleptoparasites (i.e. some can trick ants into regurgitating food for them). One of their ‘common’ names is “ant-loving beetles” – although one doubts that they are a common topic of conversation. Also, this common name does tend towards confusion with ‘ant-like stone beetles’ or Scydmaenidae, a topic in the previous post.

In any case, if you would like to spend some time reading about beetles or just looking at some pictures of them – I have good news! The first issue of a brand new blog carnival is up – An Inordinate Fondness – and it is devoted to beetles.