New Photo-Electron Challenge & Old Answers

What is my secret name and what do I want from life?

‘To-morrow, and to-morrow, and to-morrow, Creeps in this petty pace from day to day’, but at last the the tomorrow promised in the last post (in March no less) has finally arrived. I plead overwork – I’ve had two massive taxonomic projects to complete including a listing of all of the species of mites known from Alberta – before the new field season commences.  Above is one of these little monsters saying high and below are a number of them clinging to an insect collected from a rotting oyster mushroom (Pleurotus ostreatus). Any guesses to the mite, insect, spores, ecological interactions?

Mites & insect - name them both and what is happening.

ANSWER TO PHOTON CHALLENGE

I’m fairly pleased in how well everyone did in the first Photon Challenge, especially considering the quality of the pictures.  Ray even got the fly to genus and Kaitlin got pretty close to the family of the mesostigmatan – at least according to the Manual of Acarology 3rd Edition the Halolaelapidae belongs in the Rhodacaroidea and they certainly are phoretic as deutonymphs, as one would expect in that superfamily. So Kaitlin gets points for that. Bruce got the family, and, I believe, the genus correct, at least in the broad sense: Halolaelaps s.l.  Bruce has the advantage of having described the only known Australia species of the group and to have pointed out how messy the generic concepts are (see Halliday 2008 Systematic & Applied Acarology 13, 214–230). I am neutral on what superfamily Halolaelapidae belongs to – Rhodacaroidea is unlikely to be monophyletic and deutonymphal phoresy is probably a ‘primitive’ behaviour in Mesostigmata.

Deutonymph of Myianoetus - note bifurcate claws

Alas, no one guessed the genus of the histiostomatid – Myianoetus! All acarologists should know this genus if only because it contains one of the few mites to lurk among the pages (as an anoetid) of  a large circulation, general science magazine – Science itself – and the interesting concept of ‘fly factors’:

Greenberg & Carpenter (1960) Factors in Phoretic Association of a Mite and Fly. Science 132: 738-739.

“Abstract: Combined rearing of the mite Myianoetus muscarum (L.), and the fly Muscina stabulans (Fall.) has revealed adaptations of the hypopus to a series of fly factors. These adaptations favor the mite’s dispersal. Hypopi are attracted to the pupa by a volatile substance and cluster on the anterior end, from which the fly emerges.”

Read the whole thing, as they say, but, although published over 50 years ago, you will still need access to Science to do so (and to read the next paper entitled  ‘Licking Rates of Albino Rats’). Rat licking trailer aside, I think the most interesting thing about the Myianoetus paper is that I can’t remember any follow-ups that explain ‘fly factor’ or ‘beetle factor’ or ‘ant factor’. Most of the chemical clues used to induce or terminate phoretic behaviour in mites remain unknown. Only skatoles and dung beetles come to mind. If someone out there in the ether knows of other studies, please let me know – I can use the information to help a student.

Photon Challenge: Last Chance

Business end of Antennolaelaps

Well, this Photon Challenge has gone on long enough: last chance for demonstrating your acarological expertise. Tomorrow I will reveal all.

Kaitlin and Ray have done well to the family level of the histiostomatid, but I don’t think a leap to the genus is impossible. After all, just how many mite genera have made it into the pages of Science magazine?

Ray has an embarrassingly detailed grasp of the anthomyiids breeding in indelicate accumulations of organic matter. But no one seems to be willing to stick their neck out on the phoretic mesostigmatan deutonymphs with two dorsal shields that have a death grip at the base of the abdomen of the Eutrichota. Last hint: the family of the phoretic mesostigmatan is currently placed in the same superfamily as the Antennolaelaps featured above.

Photon Challenge: New Hints

A closer view of a mitey fly

Kaitlin and Ray have both demonstrated that even the smaller of the two mites hitching a ride on our fly can be identified to family from a not so great photo: heteromorphic deutonymphs (aka hypopi) of a member of the Histiostomatidae. They also correctly placed the larger mite to order: Mesostigmata. Not much luck on the fly, though, so I guess that means mites are easier to identify than flies? Anyone who has struggled with the generic key for this family in Nearctic Diptera might very well say yes. However, the family of the fly should be an easy guess for a dipterist.

Genus anyone?

Here’s a light microscope view (this is a Photon Challenge) of the venter of one of the histiostomatid hypopodes (yet another name for these deutonymphs) and a closeup of one of the pretarsal claws. The ventral shot is layered from three images in the wonderful CombineZP and the claw from two shots. The host association and characters visible in this image should give the discerning astigmatologist a good guess at the genus (I have checked with the North American authority on this one and he had no problem).

I’ll give one more hint on the mesostigmatans too – they also are deutonymphs.

Three-in-one Phoresy Photon Challenge

Name the insect and its hitch-hikers for full credit

This is the first Challenge using a light micrograph, but the usual rules apply – name the beasts as well as you can and Macromite fame may be yours. If the task proves too daunting, well then here’s a meander through the illustrated behavior to keep you entertained.

Phoresy is a behaviour, or rather a set of behaviours, exhibited by many small animals and especially by mites. The word is a bit confusing. The root, phor– is from the Greek word phoros which means to bear, to carry or refers to movement (not phor, a thief or kind of bee), but phoresy actually requires an absence of movement and it is usually not (but not always) the mite that does the carrying. Thus, the usage is a bit inverted from similarly derived jargon, e.g. the conidiophores that bear fungal spores or electrophoresis where an electrical field is used to carry charged particles through a gel or other medium. In the case of phoresy, it is the mite that is carried, usually by some lucky, larger, and more vagile arthropod.

Hypopi have no mouths but do have sucker plates

Nature is full of interesting interactions, but to study them first requires defining them. Well, perhaps not, but that is what scientists like to do – and tying them up with definitions and tagging them with a name derived from Greek or Latin (or both) is always great fun. The term phoresy was first proposed by French entomologist and bostrichid specialist Pierre Lesne in 1896 and to quote from a delightful paper (read the pdf – the web text is full of errors) by the famous myrmecophile and ant acarologist W.M. Wheeler (1919): “In 1896 Lesne called attention to a number of small insects that habitually ride on larger insects. To this phenomenon he applied the term “phoresy” and showed that it is distinguished from ectoparasitism by the fact that the portee does not feed on the porter and eventually dismounts and has no further relations with the latter.”

Lestes damselfly (male) with parasitic water mite larvae (red blobs)

As classically defined in the mid-20^th Century, phoresy required an animal to stop its normal behaviours (e.g. seeking food or members of the opposite sex), seek out a carrier, mount the carrier and refrain from doing anything other than holding on, and then after a time to dismount from the carrier and resume normal behaviours. Taking a bite out of the carrier was considered a no-no – and animals that did so were banned from phoresy and sent to parasite prison. The heteromorphic deutonymph of Astigmatina (aka hypopus) is a classic phoriont – it lacks functional mouthparts, has no foregut (and so feeding would seem to be verboten), and has a ventral sucker disk formed from modified setae for holding onto an insect or other larger arthropod (sometimes even other  mites).

So, in an evolutionary ecology sense, classical phoresy can be thought of as an ectosymbiosis in the commensal category where the mite gets a free ride and the carrier doesn’t really care. Dispersal is assumed to be at the root of the evolution of these behaviours in the mites (although phoresy may actually concentrate, rather than disperse the mites). But are things really so simple?

Again the jargon is a bit confusing: ‘commensal’ implies eating together, and the mite can’t eat while on the carrier or it wouldn’t be considered phoretic. Consider the case of water mite larvae – they use adult aquatic insects to ‘disperse’, but since they take a bite while doing so, they are considered parasites, not phorionts. Then there are the strange hypopi of Hemisarcoptes cooremani which hitch rides under the elytra of ladybird beetles in the genus Chilochorus. Since Chilochorus beetles like to eat mites, this seems like a dangerous thing to do – but hypopi of H. cooremani that do not find a beetle die. Those that do find a beetle hang on for 5-21 days and swell up before leaving the beetle. Marilyn Houck (1994), who has studied this interaction, has suggested that beetle hemolymph (reflexive bleeding is a defense of many ladybird beetles – pick them up and noxious yellow blood oozes from their leg joints) may provide critical nutrients, possibly via the anal vestibule of the mites (which connects to a hindgut).

Another point to consider is how the porter really feels about the portees. When I look at insects covered in phoretic mites, e.g. the Photon Challenge above, I find it difficult to believe the bug is having a good time. But some bees and wasps have special mite pockets (acarinaria) that appear to have evolved to encourage mites to hitch a ride. I’ll post on acarinaria some day, but for now I will just note that some of these hymenopters do much better with their mites than without them.

Lisa Hodgkin and her colleagues at the University of Melbourne published an excellent paper last year with some interesting experimental data. They studied a bark beetle (Ips grandicollis) introduced into Australia and its phoretic mites and demonstrated that ‘phoresy’ can be both dynamic and complex. Phoretic mites were associated with both negative (adults) and positive (larvae) effects on beetle reproduction and development. Heavy mite loads were not good for female beetles, but having mites in the galleries resulted in bigger and healthier offspring. Perhaps when we are considering defining complex interactions like phoresy we should remember what Hamlet pointed out to Horatio: There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy.

References:

Lisa K. Hodgkin, Mark A. Elgar and Matthew R. E. Symonds. 2010. Positive and negative effects of phoretic mites on the reproductive output of an invasive bark beetle. Australian Journal of Zoology, 2010, 58, 198–204. http://www.publish.csiro.au/paper/ZO10034

Houck, M.A.  1994.  Adaptation and transition into parasitism from commensalism: a phoretic model. In: (Houck, M.A., ed.), Mites. Ecological and evolutionary analyses of life-history patterns. Chapman and Hall, New York: 252-281.

P. Lesne. 1896. Moeurs du Limosina sacra. Phenomenes de transport mutuel chez les animaux articules, Origine du parasitisme chez les insectes Dipteres. Bull. Soc. Ent. France 45, 1896, pp. 162-165.

WM Wheeler. 1919. The phoresy of Antherophagus. Psyche Boston Volume: 26: 145-152.
http://psyche.entclub.org/26/26-145.html

Living the straight and narrow

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.

Mites and Ladders

Koalachirus perkinsi (Domrow) - the koala fur mite

Most mammals have mites that live in their fur and that don’t usually seem to do them much harm.  People don’t have these mites, probably because we don’t have much fur, but other primates do.  These ectosymbionts are highly specific to their particular hosts and are modified in various ways to cling to their hosts hairs.  They slide up and down the hair to access their food (which mostly seems to be oils and other fatty materials) and probably to regulate their temperature.

 

In the case of the koala fur mite, Koalachirus perkinsi (Domrow), the first two pairs of legs and their bases tightly clasp a hair of the host (you can see a ventral view of the mite with the groove that receives the hair here).  This particular mite came from a sickly koala at a rehabilitation centre.  Too ill to spend much time grooming (which usually keeps the population in check), the koala was literally crawling with mites and I was brought a large vial of them to identify.

 

Much to my surprise, when I opened the vial a horde of mites scrambled out and dashed helter-skelter across my desk.  Although the front legs look inappropriate for mad dashing, they have slender pretarsi that are folded out of the way when riding the hair.  When unfolded they are capable of surprising bursts of speed, which I suppose helps them get from one koala to another.

A mite with a mite problem

5 hypopi hitching a ride on an Athiasiella

This morning Myrmecos Blog, the place to go for spectacular ant pictures, links to a picture on Flickr by Brian Valentine of a couple of red ants from a compost heap covered with mites. I especially like the ones sticking to the foreground ant’s eye. These look like the dispersal stage of another Astigmatina, possibly a species of the acarid genus Sancassania, as they are common in decomposing material, but then so are several other families. If the compost is very wet and stinky, then they may be Histiostomatidae. The dispersal stages are technically called ‘heteromorphic deutonymphs’, but an older term ‘hypopus’ (plural – hypopi) is easier on the tongue. Hypopi are bizarre for a number of reasons. For example, most have some of their posterior ventral setae modified into a sucker plate that allows them to latch onto surfaces such as insect cuticle – or that of larger mites for that matter. Actually anthing with an appropriate surface that wanders through a compost heap can become covered with [these] little hitchhikers – the famous Australian medical acarologist, Bob Domorow, once published a picture in Acarologia of a skink absolutely encased in [hypopi] CORRECTION – deutonymphs, yes, but of a uropodid mite, not astigmatine hypopi.  See Domrow, R. 1981. A small lizard stifled by phoretic deutonymphal mites (Uropodina). Acarologia 22:247–52

Hypopus underside – note tiny ‘head’ and sucker plate (bottom)

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House Dust Mite

A house dust and flour mite - Dermatophagoides farinae

Although the world is filled with spectacular and mostly beneficial or harmless mites, most of the image requests that I get are for those relatively few species that cause us harm.  Here’s one that sort of causes us harm, one of the inhabitants of our house dust Dermatophagoides farinae Hughes.  Unlike what you might think from its generic name, Dermatophagoides don’t really eat our skin, but more like munch on the microbes that grow on the skin flakes we castoff with abandon wherever we go.  The species name, farinae (Latin for ‘of flour’), however, is indicative of where else you might find this mite.  This particular specimen came out of a packet of cake mix along with a few million compatriots and caused an unfortunately allergic baker to go into anaphylactic shock.  Although this mite is harmless itself, it’s skin and faeces are highly allergenic to some.

As I mentioned before, I find white the most difficult colour to manage.  In life, the body of this mite is a translucent whitish colour that I have never been able to successfully reproduce.