Who likes shrews? These mites do!

My friend Allan Lindoe, fossil preparator extraordinaire, lives on an acreage near Athabasca and makes the journey south to Edmonton about once a week to carefully remove rocky matrix from around the skeletons of long-dead fishes, mosasaurs, and dinosaurs. Two cats share his home and frequently bring him presents of wild game. A few weeks ago I washed a mixed bag (literally) of a dozen shrews he had accumulated over the summer and fall of 2015. Chewed-on shrews are not easy to identify unless you know a lot about insectivore teeth, but based on tail length and known distributions of shrew species in Alberta, they were one or more of the masked shrew (Sorex cinereus), Arctic shrew (S. arcticus), pygmy shrew (S. hoyi) and/or dusky shrew (S. monticolus)*. Some of the shrews were rather decomposed, so I wasn’t expecting much from the washings, but I was pleasantly surprised: 6 species of mites! Members of both major lineages were present. From the Acariformes were Prostigmata (Myobiidae, Pygmephoridae and Trombiculidae) and Sarcoptiformes (Glycyphagidae). From the Parasitiformes there were larval hard ticks (Ixodida: Ixodidae) and what look like Melicharidae (Mesostigmata).  Myobiids, trombiculids, and ixodids are parasitic, and the others are all likely just phoretic. Who knew the zoo on shrews? Now you do.

Protomyobia nr. claparedei female (note egg).

 

Protomyobia nr. claparedei male (note well-sclerotized aedeagus).

 

Larval Protomyobia nr. claparedei (note styletiform chelicerae).

 

Ventral view of one of the many pygmephorids from the shrew washings.

 

Pygmephorid showing modified legs I.

 

Dorsal view of a shrew chigger (Trombiculidae).

 

Prodorsal shield of a shrew chigger, showing the posterior pair of trichobothria and single anterior median seta (just the base can be seen here) indicative of the family Trombiculidae, as opposed to members of the Leeuwenhoekiidae, which have two anterior median setae.

 

An Oryctoxenus sp. deutonymph (Glycyphagidae). Anterior is pointing up, and yes, it doesn’t have mouthparts.

 

Posterior hair-clasping structures of an Oryctoxenus deutonymph.

 

A larval hard tick (Ixodidae).

 

Retrorse spines on the tick’s hypostome help keep it attached to the host.

 

Maybe a female Proctolaelaps sp.(Melicharidae). Not in great shape.

 

The ‘procto’ part of Proctolaelaps refers to the large anal opening, or so the etymological legend goes.

*Smith, H.C. 1993. Alberta Mammals: an Atlas and Guide. The Provincial Museum of Alberta, Edmonton, Alberta.

 

 

A Less Notorious Bee Mite

The mite Varroa destructor has become famous in the wake of colony collapse disorder as a nasty parasite of the domestic honey bee Apis mellifera. But it is not the only bee-associated member of the family Varroidae, nor is A. mellifera the only host of varroids. Last week a former honours student of mine, Dr. Geoff Williams, sent me specimens of Euvarroa from a nest of the dwarf honey bee Apis florea Fabricius from just north of Chiang Mai in Thailand, where they had been collected by a local student, Patcharin Phokasem.

Like Varroa, Euvarroa are very large, heavily sclerotized mites. The ones that Geoff sent were 1 mm long: five Notoedres from a mangy squirrel skin could lie nose-to-tail on the venter of one Euvarroa.

Euvarroa sinhai is a big mite, shown here with a 200 um long Notoedres for scale.

There are two named species in the genus Euvarroa, E. sinhai Delfinado & Baker and E. wongsirii Lekprayoon & Tangkanasing. Euvarroa sinhai is associated with Apis florea, whereas E. wongsirii is found on A. andreniformis Smith.  The species differ in general body shape (very triangular for E. wongsirii) and length:width ratio for the anal plate (longer than wide in E. sinhai, the opposite for E. wongsirii)*. Based on these host and morphological features, the mites from Geoff are E. sinhai.

I don’t think that much is known of the biology of either Euvarroa species, but they are very spiffy-looking mites. Here are some closer views of parts of their anatomy.

The bee-piercing chelicerae of Euvarroa sinhai.

Euvarroa sinhai‘s u-shaped peritreme; stigma to the upper left.

“My, what big ambulacra you have!” “All the better for holding onto bees, my dear.”

*Lekprayoon, C. and P. Tangkanasing. 1991. Euvarroa wongsirii, a new species of bee mite from Thailand. International Journal of Acarology 17: 255–258.

Mystery of the Mangy-Squirrel Slurry

A few years ago I worked with members of the Vancouver Rat Project to investigate the cause of lumpy ears in rats from one of the shipping ports in that city. The rodents turned out to have ear mange caused by the sarcoptid mite Notoedris muris (Astigmata: Sarcopidae). As far as we could tell, this was the first record of N. muris in Canada. About two weeks ago, one of the co-authors of this paper, Jamie Rothenburger (now a Doctor of Veterinary Medicine doing her Ph.D. at the University of Guelph in Ontario), emailed to ask if I could look at a chunk of skin taken from a mangy squirrel. Jamie suspected Notoedres centrifera Jansen. This sarcoptid species has been reported to cause mange in many species of sciurids in North America and may be hindering recovery of the western gray squirrel.

Diagnosis and drawings of Notoedres centrifera from Klompen (1992).

Jamie had only histological sections through mangy squirrel skin, though, which are difficult to match to species descriptions. I said sure and soon received a small frozen chunk of integument via courier. The skin sat in a saturated KOH solution for a couple of days to encourage its dissolution. The single mite I managed to find in the smelly skin slurry matched Klompen’s illustrations of N. centrifera (above), and was a similar size (200 um).

Ventral view of the sarcoptid mite I found in the squirrel slurry.

Dorsal view of same.

So, diagnosis confirmed, end of story, right? Well, actually, the mite isn’t the reason for the ‘mystery’ in the title of this post. In addition to the one tiny Notoedres, I found several almost as miniscule (600 um), translucent cigar-shaped objects in the digested squirrel skin. Out of curiosity, I mounted three of them yesterday. [UPDATE: I revisited the slurry and found a fourth critter, images of which are at the bottom of the post]. Today I spent several hours futilely trying to pin them down to a taxon finer than ‘probably some sort of arthropod’. My first thought as I mounted them was follicle mites (Demodicidae) in cysts, but nope, not enough legs. There seem to be only two pairs! Plus they end in single large claws or clawlike tarsi, whereas follicle mites have two small claws per leg. Embryonic insects in eggshells? Still not enough legs, unless the first pair develop much more slowly than the last ones. Maybe…see third photo below. What insects might be on squirrels? The critters don’t look much like lice, because to my knowledge no lice have a big tuft of bum setae. And what are those weird flash-shaped setae at the head end? Are those round things spiracles? And why is there scalloped ornamentation on the bases of the four well-developed legs? None of the many entomology texts I consulted had images at all similar to these.

Ventral view of one of the four-legged embryos (?) from the squirrel skin. Note the long whippy bum setae (I assume that’s the bum end).

Lateral view of one of the other embryos.

It looks like there might be another pair of very poorly sclerotized anterior legs, with the faint leg tips clasping on of the more posterior legs.

Flask shaped setae on the head-ish end.

Something that might be an anterior spiracle.

 

A row of abdominal spiracles?

There’s a fan-shaped structure at the base of each of the sclerotized legs (most clear on second leg from the right). They remind me of the ventromental plates of chironomid larvae.

I managed to mount one of the mystery critters with legs spread out and saw that the fan is actually split, like an open bivalve shell. Note also the trachea.

At the anterior end of the thing are two sets of what look like trichobothrial bases, but there are no trichobothria or other setae coming out of them on any of the four critters that I mounted.

 

I am thoroughly stumped. Help!

Reference:

Klompen J.S.H. 1992. Phylogenetic Relationships in the Mite Family Sarcoptidae (Acari: Astigmata). Museum of Zoology. Ph.D. thesis, The University of Michigan, Ann Arbor, MI, USA.

Is That a Wombat on Your Belly, Or Are You Just Happy to See Me?

I attended a Ph.D. defense a few weeks ago on the effects of salmon lice (which are copepods, not insects) on their juvenile hosts. The student showed some gory photos and pointed out that for such a little fish, carrying a louse was like a human lugging around a raccoon on his back. Some mites can be just as burdensome, such as this Macrocheles muscaedomesticae (Scopoli) attached to the abdomen of an unfortunate Drosophila hydei Sturtevant.

Scanning electron micrograph of a Drosophila hydei carrying a female Macrocheles muscaedomesticae (image by HP)

Females of many species of Macrocheles (Mesostigmata: Macrochelidae) hitch rides on winged insects to move from a place to place, a phenomenon called phoresy. Strictly phoretic organisms do not feed on the host while attached. A great many mite taxa fall into this ‘purely phoretic’ category. Others may facultatively snack on the host while in transit. My colleague Lien Luong has investigated one such mite species, Macrocheles subbadius (Berlese), and its cactus-associated host Drosophila nigrospiracula Patterson & Wheeler. When Lien moved to the University of Alberta it proved difficult to replicate the system, in part because cacti are not common in this part of Alberta.  Compost bins are abundant, however, and Lien and her students are investigating the ecological relationship between two compost-associated species, Macrocheles muscaedomesticae and Drosophila hydei. Does M. muscaedomesticae feed on its host while attached, or is it just holding on? One way to test this is to determine whether the mite’s mouthparts pierce the fly’s integument. In this N = 1 sample, the mite just seems to be holding on firmly, probably uncomfortably so from the fly’s point of view.

Piercing or just pinching?

 

Looks like pinching, probably painfully.

But by definition, facultative parasites aren’t always parasitic. More mites must be examined, and other lines of evidence followed, such as presence of melanized wounds on hosts after the mites have dropped off, or presence of Drosophila DNA in the guts of the Macrocheles.

 

Brazilian Beauties

A couple of weeks ago my colleague Fabio Akashi Hernandes* from the Universidade Estadual Paulista sent me the file for a poster that I immediately printed on high-gloss paper and proudly affixed to the door of my office. The poster depicts some of the feather mites that Fabio has found on birds from Brazil and a few other tropical countries. Eye candy for acarologists! They are all scaled to the mm mark at bottom right, where you can see the gigantic Laminalloptes phaetontis (Fabricius) from tropicbirds. Among the selected mites are the hoatzin-dwelling Opisthocomacarus umbellifer (Trouessart) (mite #40) in which both sexes are adorned with feather-like setae of unknown function. Typically, though, male feather mites are more elaborate than females. The poster includes species whose males have vicious-looking hind legs (e.g., 1, 28), or are asymmetrical (e.g., 31, 32, 58), or are very well-endowed (20).

Fabio is doing some marvelous work on taxonomy and ecology of these mites, including the very recent discovery of a host-switch from wild cuckoos to domestic poultry. But even though he and his colleague Michel Valim have been working hard to describe new species, at least 80% of bird species in Brazil have yet to be investigated for their acarofauna. Many more wonders await.

Click on the poster image then mouse over and click to magnify.

*abakashi@gmail.com

Two Bad Mites

This August I met two of the most important mite pests in North America. The two-spotted spider mite, Tetranychus urticae Koch (Prostigmata: Tetranychidae) is particularly devastating in greenhouses. That’s where I encountered it – slaughtering my dill. The common name ‘spider mite’ refers to the vast quantities of webbing they produce.

Tetranychus urticae and its webbing on my unfortunate dill plants.

Closer view of webbing, showing the mites themselves.

This spider mite has a huge host range, having been recorded from more than 1000 plant species. It feeds by piercing host tissues with its fine stylet-like mouthparts.

Tetranychus urticae female: above, whole body; below, gnathosoma showing stylet-like chelicerae.

The name ‘Tetranychus‘ means ‘four claws’ and presumably refers to the four nail shaped setae (tenent hairs) on the tarsi. Why ‘urticae‘? Because they are irritating, like nettles (Urtica spp.)? Or maybe they were first identified from urticaceous hosts?

Four nail-like tenent hairs can be seen at the tip of this mite’s tarsus.

Tetranychus urticae has made the big journals lately for having the smallest known genome of any arthropod, and for having likely picked up genes for producing carotenoid pigments by horizontal transfer from fungi. Until recently, it was thought that all animals acquired carotenoids from plants, bacteria or fungi in their diets rather than creating the pigments through their own metabolism. But pea aphids and T. urticae are able to make carotenoids themselves, thanks to these horizontally transferred genes.

The other bad mite I met in August has a much narrower host range – bees of the genus Apis, including the domesticated honeybee Apis mellifera Linnaeus.  This mite is the infamous Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae). These parasites are huge relative to their hosts, being about the size of the bee’s eye. They feed on host haemolymph, thereby weakening the bee, and can transmit crippling viruses. Although I don’t have honeybee hives in my backyard, one of my previous graduate students is a member of YEG Bees and was taking part in the first trial of urban bee-keeping in Edmonton. He invited me to one of their hive checks. Part of the check involved looking at the sticky boards under the hives for Varroa that had been knocked off the bees. Sure enough, they were there. I collected a couple and managed to get an ok photograph of one of the vaseline-covered mites.

A Varroa destructor from Beeyonce’s hive. The queen of the other hive I visited was named Justin Beeber. Beeber’s hive failed – prophetic?

A V. destructor, after having had vaseline removed via a fine probe and Photoshop.

Varroa can be treated with chemicals or through careful selection of mite-free brood starters. But it is getting harder to find the latter, as V. destructor is found in almost every Apis mellifera-producing country except Australia.  Researchers and apiarists are also trying to breed a more Varroa-resistant honeybee by selecting for intense grooming behaviour.

On the one hand, these two species tarnish the image of other mites through their economic nastiness. But on the other, their bad behaviour helps to pay the salaries of many acarologists.

 

 

Inquisitive and very very fast

Speedy anystids are in the media this week because of a recent presentation at the Experimental Biology meeting in San Diego. The now famous whirligig mite is Paratarsotomus macropalpis (Banks), a member of the anystid subfamily Erythracarinae. Erythracarines have a more elongate body than species in the Anystinae (one of which is by the ‘The” in this blog’s title) and often have very attractive striped legs, such as this individual from New Zealand (photo by S.E. Thorpe from Wikimedia Commons). Rubin et al., the authors of the abstract, clocked Paratarsotomus macropalpis running on hot pavement at 0.8 km/h, which doesn’t sound impressive until this is converted into body lengths: 322 body lengths/second. As National Geographic reports, this is much greater than a cheetah can achieve (16 body lengths/s), and faster than what they state is the previous record holder, a tiger beetle (171 b.l./s).  But what about the copepods that were celebrated only as few years ago as being able to leap through water (!) at 500 body lengths/s? Maybe it doesn’t count because it isn’t sustained running? Or do aquatic animals keep their own statistics? Irrespective of such semantic quibbles, it’s wonderful to see anystids getting press for their athletic achievements.

It drinks!

In fact, the UNAM Chamela opilioacarids are thirsty creatures.  Rather surprising for what appears to be a dry-adapted species.

Opilioacarid drinking from a water droplet in its vial.

Size and eyes

Yesterday we collected 17 live opilioacarids from under stones near the Chamela station greenhouses.  Their light purple colour makes them stand out relatively well against the reddish soil encrusted on the bottoms of the rocks. But they are pretty small and getting one off a rock can involve quite a chase with a paintbrush as they dash in and out of crevices. In case you want to know how big they are, here is a photo of one in a vial with my left index fingerprint for scale. The closeup shows how the camera’s flash is reflected by a tapetum in the eye of the mite – a feature unique to opilioacarids among both parasitiform and acariform mites. In spiders, presence of a tapetum seems be an adaptation for night vision (but not all nocturnal spiders with good vision have a tapetum according to this  Australian Museum post). Does the tapetum in opilioacarids mean that they come out from under rocks at night? Or that they use these fancy eyes to better navigate their dark sublithic world?

It walks!

Guess where you can get plenty of live opilioacarids? In the Viveros area of the Chamela field station, just next to the greenhouses, under rocks. It is with pride and some surprise that I present the very first Youtube video of a Neocarus* walking across a piece of herbarium paper.

*thanks to Bruce Smith for correcting my previous typo – Neoacarus is a water mite genus, Neocarus is the opilioacarid.