Endeostigmata

t

Taxonomy

Diagnosis

Prodorsum with 2 pairs of trichobothria (sci, ve) and 2–4 pairs of setae (in and/or exp may be absent); sci and ve either filiform or capitate; naso nude, reduced; lateral and median eyes present or absent. Rutella present or absent; chelicerae chelate-dentate to attenuate-edentate, each with 0–2 setae. Opisthosoma usually hypertrichous; 3 pairs of genital papillae. Leg IV not modified for jumping.

Remarks

This is the most difficult family of Endeostigmata to diagnose because of the remarkable variation in characters and it may not be a natural group. A fossil species is known from the Devonian Rhynie Chert and many extant species appear to be among the most plesiotypic Endeostigmata known. Some species of Alycus feed on nematodes (Walter 1988cWalter 1988c:
Walter DE. 1988c. Predation and mycophagy by endeostigmatid mites (Acariformes: Prostigmata). Experimental and Applied Acarology 4: 159–166.), which usually do not form visible gut contents, but others have gut boluses with fungal material. An unidentified species of 'Pachygnathus' from the intertidal is reported to have gut boluses with the cuticle of copepods and tardigrades (Schuster 1979Schuster 1979:
Schuster R. 1979. Soil mites in the marine environment. pp. 593–602. In: Rodríguez JG, ed. Recent advances in Acarology, Volume 1. Academic Press, New York.). Although probably the most commonly encountered genus of Endeostigmata in forest litter, and certainly the largest in body size, the feeding biology of Bimichaelia is unknown. These mites have elongate, needle-like chelicerae and, although an occasional specimen with a fungal spore impaled on the tips of the chelicerae has been found, no one has reported any feeding observations. Theron speculated that species of Bimichaelia might suck juices from plant roots (Theron 1979Theron 1979:
Theron PD. 1979. The functional morphology of the gnathosoma of some liquid and solid feeders in the Trombidiformes, Cryptostigmata and Astigmata (Acarina). pp. 575–579. In: Piffl E, ed. Proceedings of the 4th International Congress of Acarology. Akadémiai Kiadó, Budapest.), and Lindquist expanded on the possible evolution of phytophagy in the Bimichaeliidae and the similarity of their mouthparts to those in Eriophyoidea (Lindquist 1998Lindquist 1998:
Lindquist EE. 1998. Evolution of phytophagy in trombidiform mites. Experimental and Applied Acarology 22: 81–100.). Although an intriguing idea, perhaps feeding on ectomycorrhizae is more likely.

References

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