Hydrachna piersigi Koenike, 1897

Davids, Kees, Sabatino, Antonio Di, Gerecke, Reinhard, Gledhill, Terence & Smit, Harry, 2005, On the taxonomy of water mites (Acari: Hydrachnidia) described from the Palaearctic, part 1: Hydrachnidae, Limnocharidae and Eylaidae, Zootaxa 1061, pp. 36-64 : 48-49

Hydrachna piersigi Koenike, 1897

Species incerta

Material examined: Holotype male NMHB Koenike 551, "Großzschocher, Piersig coll. Type ".

Discussion: The idiosoma and gnathosoma of the holotype are badly damaged by fragmentation, compression and strong clearing (probably by heat and chemical agents).

As a consequence, the shape of the gnathosoma and genital field can not be recognized. Numerous remnants of the dorsal cuticle are mounted, but in an unclear topographical relation. One of these pieces includes a setal sclerite similar to the crescent­shaped postocularia of H. processifera , but the extension of sclerotisation might have changed due to treatment before slide­mounting. Also, the shape of the gonopore and several measurements (L gnathosoma rostrum 700, chelicera 1180, P­3 230, P­3 450, P­4 140) indicate that the specimen might be more related to H. processifera than to the generally bigger members of the geographica group. However, H. piersigi differs from H. processifera in having a more slender palp. The frontal area being damaged, a reexamination of this taxonomically important part of the idiosoma is not possible. Phylogenetic relationships to other species cannot be excluded and no final decision about diagnostic features of H. piersigi is possible. It must be regarded a species incerta.