Endeostigmata

Superorder Acariformes

  Order Sarcoptiformes

     Suborder Endeostigmata

       Cohorts (Superfamilies): Alycina (Alycoidea), Nematalycina (Nematalycoidea), Terpnacarina (Oeserchestoidea, Terpnacaroidea), Alicorhagiina (Alicorhagioidea)

 

Common names: endeostigmatans

 

Probability of Encounter: medium

 

Quarantine importance: None.  Most endeostigmatans are rare and all that have been studied are fungivores, algivores or predators of small invertebrates.  Many species appear to be ancient thelytokous lineages with cosmopolitan distributions.

 

Diagnosis.  Soft-bodied, sometimes hypertrichous, acariform mites, often with remnants of primary segmentation.  Body cuticle usually plicate, sometimes with secondary ornamentation; colorless (white) to pale lilac, bright pink or yellowish brown.  Prodorsum unsclerotized, usually with 5-6 pairs of setae (Vertex-scapular system: vi, ve, sci, sce, in, exp; also, Rostral-bothridial system, respectively: ro, le, bo, exa, in, exp) and, except in the usually worm-like Nematalycidae, prodorsal setae sci (and sometimes sce) formed as trichobothria; dorso-sejugal furrow distinct; naso and/or median eye often present; lens-like lateral ocellus and post-ocular body often present.  Subcapitulum with lateral lips bearing 0-3 pairs of adoral setae, narrow rutella with distal blade or teeth; 2-3 or more pairs of setae in the genal area; and usually a pair of peg-like epicoxal setae (ep); palps usually with 5 free segments (sometimes with femora subdivided) and without a palptibial claw.  Chelicerae often distinctly 3-segmented (trochanter well developed), chelate-dentate to attenuate-edentate stylets and bearing 0-2 setae; subcapitulum sometimes suctorial.  Genital shields unsclerotized, bearing numerous genital setae, and covering 3 (rarely 2) pairs genital papillae in the adult.  Legs well supplied with solenidia and other setae, but without trichobothria; epicoxal seta epI sometimes present; pretarsi usually with empodium and often with claws; legs IV often modified for jumping.

 

Similar mites.  Some endeostigmatans resemble small, soft-bodied prostigmatans (especially members of the Eupodina), but usually have rutella and 6 rather than 3-5 prodorsal setae.   Species of Nanorchestidae (Speleorchestes, Nanorchestes) are especially common in very dry habitats (sand dunes, hot desert soils, cold deserts) and can be distinguished by their 2 pairs of prodorsal trichobothria and heavily sclerotized, finger-like labrum.  Members of the Terpnacaridae resemble soft-bodied oribatid mites.

 

Ecology & Distribution.  Endeostigmatans are mostly tiny, globular or bizarrely elongate sarcoptiform mites that bear numerous primitive morphological characters.  They are often found in extreme soil habitats (e.g. cold and hot deserts, microbial crusts, seashores, sandy soils, deep soil).  Fossil endeostigmatans have been described from some of the earliest terrestrial faunas known, and their life styles tend to reflect their early derivation.  For example, most endeostigmatans have the fundamental acariform ontogeny, i.e. an egg, an inactive hexapod prelarva, an active hexapod larva, and active octopod protonymph, deutonymph, tritonymph and adult.  In some taxa the prelarva is retained within the egg; but in others it expands, pops the egg shell, and then remains quiescent.  In some Nanorchestidae the prelarva is able to move, but not feed.  The stage between molts is quiescent and unable to move.  The number of eggs matured at one time by a female seems to vary with size: small species tend to mature a single egg and large species many.  A short ovipositor is primitively present, but has been lost in many groups.  Males usually have a well developed spermatophoric organ for producing spermatophores, but all female parthenogenesis is common in the Terpnacarina and males are unknown for many taxa.  In Alicorhagia, silken cocoons are spun for the deposition of eggs and before molts.  Cocoons of other endeostigmatans can be found in soil extractions using flotation methods.

In the Terpnacarina and Alicorhagiina larvae and other active stages feed by ingesting pieces of solid food (i.e. particulate feeding) which form discrete gut boluses, a behavior shared with some Opiliones, opilioacarans and sarcoptiform mites.  Within the Terpnacarina, fungi and sclerotized bits of small invertebrates can be identified in gut boluses.  Outside of the Terpnacarina little is known about feeding biology.  Some Bimichaeliidae (e.g. Alycus roseus Koch) appear to be exclusively predatory on nematodes, but others (e.g. Bimichaelia) have highly modified, elongate, needle-like digits that serve an unknown function.  The Nanorchestidae are fluid-feeders and have a sclerotized tubular labium with an unknown function.  Nanorchestes amphibius Topsent & Trouessart is reported to feed on green algae.

 

References

Gilyarov, M.S. (ed.) 1978.  Identification key of soil inhabiting mites. Trombidiformes.  Nauka: Moscow [In Russian].

Grandjean F.  1939.  Quelques genres d’acariens appartenant au groupe des Endeostigmata.  Ann. Sci. nat. Zool.  11(ser. 2):1-122.

Kethley JB.  1982.  Endeostigmata.  pp. 118-120, In: Parker SP (ed.)  Synopsis and Classification of Living Organisms.  McGraw-Hill, NY.

Kethley JB.  1990.  Acarina: Prostigmata (Actinedida).  pp. 667-756, In: DL Dindal (ed), Soil Biology Guide.  John Wiley & Sons, Brisbane.

Krantz GW.  1976.  A Manual of Acarology.  OSU Bookstores: Corvallis.

Walter DE.  1988.  Predation and mycophagy by endeostigmatid mites (Acariformes: Prostigmata).  Experimental & Applied Acarology 4: 159-166.

Walter DE.  2001.  Endemism and cryptogenesis in 'segmented' mites: A review of Australian Alicorhagiidae, Terpnacaridae, Oehserchestidae, and Grandjeanicidae (Acari: Sarcoptiformes).  Australian Journal of Entomology 40: 207-218.