MM249999

The Halacaridae (sometimes split into several families) is a group of entirely aquatic mites from the Suborder Prostigmata of the Order Acariformes. The majority of the 960 species are marine, but there are many brackish and freshwater taxa as well (Bartsch 1996). Some are predatory, some algivorous, and some appear to be parasitic (e.g. Astacopsiphagus in the gills of the crayfish Euastacus spinifer).

In Australia there have been relatively few taxa of freshwater halacarids described (Harvey 1988), but this likely reflects undercollection rather than true rarity. Halacarids can be collected from sediments in standing and running water, as well as from their crayfish hosts.

The Pezidae, another family of halacaroid mites, can be differentiated from the Halacaridae by their possession of numerous small dorsal platelets bearing 10-14 pairs of stalked setae; 'typical' halacarids have at most 6 pairs of small dorsal setae (Harvey 1990).

References:

Bartsch, I. 1996. Halacaroids (Halacaroidea, Acari) in freshwater. Multiple invasions from the Paleozoic onwards J. Nat. Hist. 30: 67-99.

Harvey, M.S. 1988. A new species of Lobohalacarus from Australia (Chelicerata: Acarina: Halacaridae). Mem. Mus. Vic. 49: 363-365.

Harvey, M.S. 1990. Pezidae, a new freshwater mite family from Australia (Acarina: Halacaroidea). Invertebr. Taxon. 3: 771-781.

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

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