MM329999

Trhypochthoniids are a family of mites from the Suborder Oribatida in the Order Acariformes. This family contains numerous terrestrial and aquatic species. In Australia, representatives of Mucronothrus and Trhypochthoniellus occur in both standing and running water. Trhypochthoniellus has been collected in large numbers from floodplains and billabongs in the NT (pers. comm., B. Gunn and M. Colloff). Mucronothrus nasalishas been found in streams, springs, and the bottoms of very cold lakes throughout the world. As M. nasalis has no way of dispersing across land, this distribution indicates that its ancestor invaded water before the breakup of Pangaea (Norton et al. 1988). The gut contents of M. nasalis include filamentous algae, diatoms, hyphae, decayed vascular plants and the occasional bit of arthropod cuticle, suggesting that these mites graze on the periphyton growing on benthic substrates.

Trhypochthoniellus species have 3 claws on the tarsus and a fusiform sensillus, while those of Mucronothrus have one claw and a filiform sensillus.

Care must be taken when identifying oribatids from aquatic samples as terrestrial oribatids often fall into the water where they may be mistaken for aquatic species. One clue that you may have a terrestrial oribatid is that no aquatic species is known to have pteromorphs, the wing-like flaps above the leg bases of many terrestrial species.

References:

Colloff, M.J. and R.B. Halliday. 1998. Oribatid Mites: a Catalogue of Australian Genera and Species. Monographs on Invertebrate Taxonomy 6. CSIRO Publishing, Collingwood.

Krantz, G.W. 1978. A Manual of Acarology. 2nd edition. Oregon State University Book Stores, Corvallis, Oregon.

Luxton, M. 1987. The British oribatid mites (Acari: Cryptostigmata) of Warburton and Pearce. J. Nat. Hist. 21: 1359-1365.

Norton, R.A., D.D. Williams, I.D. Hogg and S.C. Palmer. 1988. Biology of the oribatid mite Mucronothrus nasalis (Acari: Oribatida: Trhypochthoniidae) from a small coldwater springbrook in eastern Canada. Can. J. Zool. 66: 622-629.

Walter, D.E. and H.C. Proctor. 1999. Mites: Ecology, Evolution and Behaviour. University of New South Wales Press, Sydney, New South Wales.