Prostigmata

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 female ex shrew

Protomyobia nr. claparedei female (note egg).

 

Protomyobia ex shrew

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

 

Protomyobia lv I think A

Larval Protomyobia nr. claparedei (note styletiform chelicerae).

 

pygmephorid ex shrew

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

 

pygmephorid ex shrew legs I

Pygmephorid showing modified legs I.

 

chigger ex shrew A

Dorsal view of a shrew chigger (Trombiculidae).

 

chigger ex shrew B

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.

 

prob Oryctoxenus A

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

 

prob Oryctoxenus B

Posterior hair-clasping structures of an Oryctoxenus deutonymph.

 

ixodid larva ex shrew A

A larval hard tick (Ixodidae).

 

ixodid larva ex shrew B

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

 

maybe Proctolaeleps A

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

 

maybe Proctolaeleps B

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.

 

 

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The truth about velvet mites

A few days ago, three of my colleagues independently sent me a link to The Oatmeal’s cartoon “This is a Red Velvet Mite and He is Here to Teach You About Love“. Like many of The Oatmeal’s cartoons, this is about sex and is unabashedly rude. But unlike most of his comics, the topic in this case was one on which consider myself to be somewhat expert: indirect transfer of sperm via spermatophores.

Proctor 1998 Ann Rev Ent

I hope this isn’t a copyright violation.

‘Indirect’ refers to the placement of sperm packets (typically on or in stalks of hardened exudate) on a substrate by the male, with the female then picking up the sperm herself. This can be done in a paired fashion in which the male directs his deposition to a particular female, often physically contacting the female at some point (e.g., scorpions), or it can be dissociated, in which the male and female don’t interact at all (many springtails and mites).  In addition to the taxa just mentioned, many other animals transfer sperm via substrate-associated spermatophores, including centipedes, pseudoscorpions, vinegaroons and even salamanders.

Velvet mites are members of the large acariform mite taxon Parasitengona, and can be roughly divided into the short-legged velvet mites (Trombidiina) and the long-legged ones (Erythraeina).  Many but not all have a sparse to plush coat of setae covering their red or orange bodies.  Based on the relatively little we know about sperm transfer in velvet mites, The Oatmeal got a lot of things right in his cartoon. Sperm transfer is indirect, males often lay down trails of exudates leading up to the spermatophores, females fertilize themselves, larval velvet mites are parasites, cannibalism is not uncommon (especially consumption of smaller males by larger females), and males do indeed trash the spermatophores of their competitors.  But sperm blobs are small, tidy and on stalks, not giant dripping beachballs as in the cartoon. Male dancing, if it occurs, is not particularly elaborate. And what’s this about building castles out of sticks and leaves? I’ve never read anything about that.  The author wasn’t forthcoming on the scientific source of the love-shack info. I searched Google Scholar for various combinations of “velvet mite*”, “Dinothrombium” (the velvet mite genus shown in the associated video), “mating” and “spermatophore*”. Nothing about castles. Perhaps the relevant publication isn’t in English? Or…could it be that The Oatmeal sometimes just MAKES THINGS UP?!?

wrestling Eutrombidium Microtrombidiidae Gull Lake AB 26 June 2013 A

Two Eutrombidium (Trombidiina: Microtrombidiidae) fighting for access to a grasshopper oviposition hole. Or maybe I’m just making that up.

Souvenirs

A few days ago we made it safely back to Canada after a month of collecting arachnids in Mexico.  While there we couldn’t resist picking up a few other souvenirs in addition to salticids and opilioacarids. One was a bottle of raicilla from the beautiful 400 year old town of San Sebastian del Oeste. Like tequila, raicilla is a distilled liquor made from agave, albeit from a different species in the same genus. The name may mean ‘little root’ but we’re guessing. Selling of raicilla has only recently been legalized according to this site.

raicilla and opilioacarids safe in Vancouver 6 March 2014

Raicilla and opilioacarids safe in Vancouver.

Therefore, I was legitimately able to bring in a bottle as a souvenir, along with my likewise legal container of opilioacarid mites (see permit above!). Unfortunately, the raicilla leaked a bit in my luggage, imbuing my trousers with a smoky flavour.

I also brought back some unintended mementos: clusters of itchy, supporating sores on my ankles resulting from bites of larval mites of the family Trombiculidae (Acari: Parasitengona). Trombiculids are known as chiggers in North America and scrub itch mites in Australia. As larvae, chiggers are parasites of vertebrates while as nymphs and adults they are free-living predators.  Despite common belief, chiggers do not burrow under your skin. Rather, those that bite humans usually attach only briefly and then drop off, leaving behind an itchy wad of spit that continues to cause irritation long after the wee mites are gone.

HPs right ankle with chigger bites 6 March 2014 compilation

My right ankle with chigger bites.

Why ‘Anystis’?

The name for this blog came to me while driving with Wayne Maddison from Puerto Vallarta to the UNAM field station in Chamela, Mexico. We were discussing the pros and cons of social media, and Wayne convinced me that I should try my hand at blogging.  But what to call this maiden attempt? I had been impressed by the interest-piquing obscurity of The Subulate Palpomere as a title and decided to try to emulate it with an acarine rather than coleopteran theme.  Thus arose The Inquisitive Anystid.  And simultaneously, the urge to find out the origin of the name Anystis, which is the type genus for the family Anystidae.  I enlisted the aid of several fellow mite biologists, and within about 24 hours of competitive name-hunting, Dave Walter came up with the strongest hypothesis for what the author of Anystis was thinking about when he named the genus.  You can read about it here on Dave’s Macromite blog.

anystid from La Bufa 7 Feb 2014