Astigmatina

Female Glycycometus sp., from here.

Belongs within: Holonota.
Contains: Histiostomatidae, Canestrinioidea, Hemisarcoptoidea, Acaroidea, Hypoderatidae, Psoroptidia, Glycyphagidae.

The Astigmatina are a group of soft-bodied mites lacking respiratory tracheae (Philips 1990). Many have rapid life cycles, and may be significant scavengers of decomposing matter. Most astigmatines (excluding the vertebrate-associated Psoroptidia) have a modified non-feeding deutonymph (hypopus) stage in the life cycle that is adapted for phoretic dispersal or diapause during adverse conditions. However, if conditions are suitable, protonymphs may moult directly to the tritonymphal stage of the life cycle and bypass the deutonymph instar (OConnor 2009).

The basalmost member of the Astigmatina, Schizoglyphus biroi, is known only from two specimens collected from the tenebrionid beetle Dioedus tibialis. These specimens probably represent deutonymphs due to their lack of chelicerae and ventral attachment organ but differ from deutonymphs of other astigmatines in having three rather than two pairs of genital papillae. Other distinctive astigmatine families include the Guanolichidae, a small group of strongly sclerotised, dorsoventrally flattened mites found on bat guano in the Afrotropical and Neotropical regions. The Guanolichidae are connected to the more diverse Histiostomatidae by their laterally compressed, non-chelate chelicerae, and transverse oviporus in the female with the genital valves open anteriorly and fused to the body posteriorly (OConnor 2009).

Life in the fast lane
Published 21 July 2010

Amongst the bewildering diversity of mites inhabiting this world, the Astigmata include some of the most significance to humans. This group of 5000+ species (with doubtless many more waiting to be described) has become specialised for rapid development and high fecundity. Originally scavengers on decomposing organic matter, members of some lineages have become parasites on vertebrates.

Dust mites Dermatophagoides pteronyssinus on a bedsheet. Dust mites are common inhabitants of human houses where they feed on particles of organic matter such as flaked skin. For the majority of people, their presence in the house is of no consequence; an unfortunate minority suffer allergies to dust mite waste products. Photo from Time.

Curiously, the soft-bodied, fast-living astigmates are most closely related among other mites to the heavily-armoured, long-lived Oribatida. In fact, both morphological and molecular phylogenetic studies have indicated that astigmates are derived from within oribatids (though recovering this result in molecular analyses is dependent on the analytical method used due to the much faster evolutionary rate of astigmates; Dabert et al., 2010). Astigmates have been derived from oribatids by a process of neoteny where the characters of nymphal oribatids have been carried over to the adult astigmate (OConnor, 2009). Astigmates have also developed a highly modified deutonymph (the second nymphal stage of development) that is specialised for dispersal through phoresy (hitching a lift on some flying insect). The astigmate deutonymph (referred to by many authors as a hypopus) is generally non-feeding and the well-developed mouthparts present in the earlier protonymph become rudimentary, only to reappear when the mite moults through to the next stage, the tritonymph. In many species, if conditions are favourable and dispersal unnecessary, a protonymph may moult directly into a tritonymph, bypassing the deutonymph stage. Other species will only develop into deutonymphs if a suitable host for dispersal is available. The Psoroptidia, the main vertebrate-associated lineage of astigmates, have dropped the deutonymph from their life cycle entirely.

Deutonymphs of Chaetodactylus micheneri on a specimen of the bee Osmia californica. Though it may not look pretty, most phoretic organisms do not actually parasitise their hosts, only using them for transport. Photo from here.

While some phoretic astigmates will attach themselves to any old host, others may be very specialised. The members of the subfamily Ensliniellinae (family Winterschmidtiidae) associate solely with nest-building wasps and bees. The early stages of the enslinielline life cycle occur in the host’s brood cell and the mites reaches their phoretic stage when the host larva has matured and is ready to leave the brood cell as an adult wasp (or bee). At that point, the mites cluster in specialised pockets on the host’s body called acarinaria. In the wasp Ancistrocerus antilope, only the male wasps emerge from the cell carrying mites in acarinaria behind the wings (the females kill any mites in their brood cell while larvae); when the male mates with a female, its mite passengers abandon him to enter acarinaria around the female’s genitalia (Houck & OConnor 2001). In other wasp species, the females carry mites in acarinaria from when they emerge. When the female lays its eggs, the mites leave the acarinaria to be sealed in the new brood cells where they will mate and lay their own eggs.

The scabies mite Sarcoptes scabiei. The Sarcoptidae are a family of parasitic mites that burrow into the skin of mammals. Most species are specialists on a small range of hosts, most commonly bats (for some reason, bats carry an extraordinary diversity of parasites), but S. scabiei is a generalist species that has been found on a wide range of hosts, from humans to wombats. Photo by Louis De Vos.

You might be wondering what the wasp gets out of this arrangement as it is hard to see why it would have developed specialised structures to transport the mites if it was not benefiting somehow. And yet, at best, the mites seem to have no significant effect on their hosts; at worst, they are actively harmful, feeding on the food stores left for the developing larva or on the larva itself (though no parasitic ensliniellines have been known to cause the death of their host). Klimov et al. (2007) have suggested that acarinaria have developed not to facilitate the mites’ development but to contain them. The mites cannot break through the walls of the brood cells themselves; they can only be carried by an emerging host. If the mites cluster into acarinaria before the host emerges, they remain with already-infected individuals rather than spreading to their potentially mite-free siblings. Perhaps adaptation is not always a matter of achieving an optimum; perhaps it is sometimes simply a form of damage control.

Systematics of Astigmatina

Characters (from Philips 1990): Weakly sclerotised, slow-moving, pale; respiratory stigmata and tracheae absent, respiration occuring through cuticle. Chelicerae mostly chelate-dentate. Palps two-segmented. Idiosoma usually divided into propodosoma and hysterosoma by sejugal furrow. Hysterosoma with laterodorsal hysterosomal gland openings normally visible. Primary genital opening of both sexes occuring ventrally between the legs, flanked by two pairs of genital papillae. Oviposition occuring through this opening (oviporus) in female, but sperm received through small circular opening (bursa copulatrix) at posterior end of body. Male aedeagus supported by struts; male anal opening often flanked by pair of copulatory suckers.

<==Astigmatina [Acaridei, Acaridida, Astigmata, Atracheata, Detriticolae, Diacotricha, Insecticolae]O09
    |  i. s.: Myrmolichus greimaeW01
    |--Schizoglyphus [Schizoglyphidae, Schizoglyphoidea]O09
    |    `--S. biroiO09
    `--+--HistiostomatoideaO09
       |    |--HistiostomatidaeO09
       |    `--GuanolichidaeO09
       |         |--NeoguanolichusP90
       |         `--Guanolichus gabonensisO09
       `--+--CanestrinioideaO09
          |--HemisarcoptoideaO09
          `--+--+--AcaroideaO09
             |  `--+--HypoderatidaeO09
             |     `--PsoroptidiaO09
             `--GlycyphagoideaO09
                  |--GlycyphagidaeO09
                  |--Pedetopus [Pedetopodidae]O09
                  |    `--P. zumptiO09
                  |--EuglycyphagidaeO09
                  |    |--Euglycyphagus intercalatusO09
                  |    `--LomelacarusO09
                  |--Chortoglyphidae [Chortoglyphina]O09
                  |    |--Chortoglyphus Berlese 1884H98
                  |    |    `--C. arcuatus (Troupeau 1879) [=Tyroglyphus arcuatus]H98
                  |    |--AplodontopusO09
                  |    |    |--A. marmotaeO09
                  |    |    `--A. sciuricola Hyland & Fain 1968M-PV-G01
                  |    `--Alabidopus Fain 1967H98
                  |         |--A. asiaticusO09
                  |         |--A. hydromys Fain 1967H98
                  |         `--A. muris Lukoschus et al. 1979H98
                  |--Aeroglyphidae [Aeroglyphinae]O09
                  |    |--Aeroglyphus robustusO09
                  |    `--Glycycometus Parameswaran Pillai 1957 [incl. Austroglycyphagus Fain & Lowry 1974]H98
                  |         |--G. geniculatus (Vitzthum 1919)H98 (see below for synonymy)
                  |         |--‘Austroglycyphagus’ kualalumpurensis Fain & Nadchatram 1980C-RSV-S88
                  |         |--G. lukoschusiO09
                  |         |--G. malaysiensis (Fain & Nadchatram 1980)C-R02, C-RSV-S88 [=Austroglycyphagus malaysiensisC-RSV-S88]
                  |         |--‘Austroglycyphagus’ orientalisSH01
                  |         |--‘Austroglycyphagus’ thailandicusSH01
                  |         |--G. troglodytus (Fain & Lowry 1974) [=Austroglycyphagus troglodytus]H98
                  |         `--G. weelawadjiensis (Fain & Lowry 1974) [=Austroglycyphagus weelawadjiensis]H98
                  |--Echimyopodidae [Echimyopinae]O09
                  |    |--Echimyopus dasypusO09
                  |    |--Marmosopus mesoamericanusO09
                  |    |--Blomia Oudemans 1928H98
                  |    |    `--B. tropicalis van Bronswijk, De Cock & Oshima 1974H98
                  |    `--Marsupiopus Fain 1967H98
                  |         |--M. acrobates Fain & Lukoschus 1976H98
                  |         |--M. antechinus Fain & Lukoschus 1976H98
                  |         |--M. leporilli Fain 1969H98
                  |         |    |--M. l. leporilliH98
                  |         |    `--M. l. pseudomys Fain & Lukoschus 1976H98
                  |         |--M. michaeli Fain 1969H98
                  |         |--M. myrmecobius Fain & Lukoschus 1976H98
                  |         |--M. trichosuri Fain 1967 [=Marsupiops (l. c.) trichosuri]H98
                  |         `--M. zyzomys Lukoschus et al. 1979H98
                  `--RosensteiniidaeO09
                       |--Rosensteinia sieversiO09
                       |--MydopholeusO09
                       |--Chiroptoglyphus americanusO09
                       |--Micronychites postverrucosusO09
                       |--Cheiromelicus trochanteralisO09
                       |--Troglotacarus [Troglotacaridae]O09
                       |    `--T. hauseriO09
                       |--Lophonotacarus [Lophonotacaridae]O09
                       |    `--L. minutusO09
                       `--Nycteriglyphus Zakhvatkin 1941H98
                            |--N. bifoliumO09
                            |--N. dewae (Womersley 1963) [=Coproglyphus dewae]H98
                            |--N. miniopteri Fain 1963H98
                            |--N. pterophorusO09
                            `--N. vespertilioO09

Glycycometus geniculatus (Vitzthum 1919)H98 [=Glycyphagus geniculatusH98, Austroglycyphagus geniculatusDA07]

*Type species of generic name indicated

References

[C-R02] Corpuz-Raros, L. A. 2002. Philippine acarine biological control agents: status, bioecology and research prospects. Philippine Agricultural Scientist 85 (2): 137–154.

[C-RSV-S88] Corpuz-Raros, L. A., G. C. Sabio & M. Velasco-Soriano. 1988. Mites associated with stored products, poultry houses and house dust in the Philippines. Philippine Entomologist 7 (3): 311–321.

Dabert, M., W. Witalinski, A. Kazmierski, Z. Olszanowski & J. Dabert. 2010. Molecular phylogeny of acariform mites (Acari, Arachnida): strong conflict between phylogenetic signal and long-branch attraction artifacts. Molecular Phylogenetics and Evolution 56 (1): 222–241.

[DA07] Domes, K., M. Althammer, R. A. Norton, S. Scheu & M. Maraun. 2007. The phylogenetic relationship between Astigmata and Oribatida (Acari) as indicated by molecular markers. Experimental and Applied Acarology 42 (3): 159–171.

[H98] Halliday, R. B. 1998. Mites of Australia: A checklist and bibliography. CSIRO Publishing: Collingwood.

Houck, M. A., & B. M. OConnor. 1991. Ecological and evolutionary significance of phoresy in the Astigmata. Annual Review of Entomology 36: 611–636.

Klimov, P. B., S. B. Vinson & B. M. OConnor. 2007. Acarinaria in associations of apid bees (Hymenoptera) and chaetodactylid mites (Acari). Invertebrate Systematics 21 (2): 109–136.

[M-PV-G01] Montiel-Parra, G., G. A. Villegas-Guzman, M. Vargas & O. J. Polaco. 2001. Mites associated with nests of Neotoma albigula Hartley, 1894 (Rodentia: Muridae) in Durango, México. In: Halliday, R. B., D. E. Walter, H. C. Proctor, R. A. Norton & M. J. Colloff (eds) Acarology: Proceedings of the 10th International Congress pp. 586–593. CSIRO Publishing: Melbourne.

[O09] OConnor, B. M. 2009. Cohort Astigmatina. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 565–657. Texas Tech University Press.

[P90] Philips, J. R. 1990. Acarina: Astigmata (Acaridida). In: Dindal, D. L. (ed.) Soil Biology Guide pp. 757–778. John Wiley & Sones: New York.

[SH01] Sumangala, K., & M. A. Haq. 2001. Survey of the mite fauna associated with Apis spp. in Kerala, southern India. In: Halliday, R. B., D. E. Walter, H. C. Proctor, R. A. Norton & M. J. Colloff (eds) Acarology: Proceedings of the 10th International Congress pp. 565–568. CSIRO Publishing: Melbourne.

[W01] Wurst, E. 2001. The life cycle of Lemanniella minotauri n. sp. and the erection of the new family Lemanniellidae (Acari: Astigmata). Stuttgarter Beiträge zur Naturkunde Serie A (Biologie) 621: 1–34.

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