MORPHOLOGY OF LARVAE, DEUTONYMPHS, AND ADULTS OF THE WATER MITENAJADICOLA INGENS(PROSTIGMATA: PARASITENGONA: HYGROBATOIDEA) WITH REMARKS ON PHYLOGENETIC RELATIONSHIPS AND REVISION OF TAXONOMIC PLACEMENT OF NAJADICOLINAE

Abstract

Adults and deutonymphs of Najadicola ingens (Koenike) are redescribed and larvae are described for the first time. In light of larval, deutonymphal and adult character states, the phylogenetic relationship of Najadicola with genera in the families Pionidae and Unionicolidae is re-evaluated and transfer of the subfamily Najadicolinae to Pionidae is proposed. Original life history information is presented to supplement existing literature. Parasitism by larval N. ingens on an adult chironomid of the genus Polypedilum is reported. The unique behavioural and morphological characteristics of members of Najadicola suggest that mussel parasitism evolved independently from a parallel adaptive sequence in the genus Unionicola.

A new Najadicola species (Acari: Hydrachnidia: Pionidae) from Asia

“…The inner margin of this group is rounded (vs inner margin forming an angle in N. ingens). The posterior margin is markedly thickened and bears a process headward laterally from the central axis of the body (vs figures of various different sources contain conflicting information: compare Koenike 1895 (one can notice a process at the image of a male) and Simmons & Smith 1984 (no process at the posterior coxal group). The apodemes of anterior coxal groups almost absent (as it has been reported for N. ingens).…”

“…The subfamily Najadicolinae Viets, 1935 contains a single monotypic genus, Najadicola Piersig, 1897 (Simmons & Smith 1984;Viets 1935). Its only species, Najadicola ingens (Koenike, 1895), has been described from Quebec, Canada (Koenike, 1895) but later was found to be widespread throughout eastern North America from Mexico to Canada (Humes & Jamnback 1950;Simmons & Smith, 1984). Furthermore, Vidrine & Lieux (1980) reported an unexpected discovery of this species in tropical Asia, i.e.…”

“…Najadicolinae and Unionicolinae have been considered as sister groups within the family Unionicolidae (Simmons & Smith 1984), they are unique water mites which are molluscan symbionts (Edwards & Vidrine 2013). However, Simmons & Smith (1984) suggested, that this genus may be closer to family Pionidae rather than to Unionicolidae based on synapomorphy in morphology and number of acetabular plates of adults and shape and chaetotaxy of the excretory pore of larvae of both families Ecologica Montenegrina 24: 32-37 (2019) This journal is available online at: www.biotaxa.org/em (Simmons & Smith 1984). However, DNA sequences of Najadicola are still lacking, and a taxonomic position of this genus is in need of the future studies by means of a molecular approach.…”

“…Vidrine opined that Najadicola from various molluscan hosts from different continents would probably reveal several species complexes (Gledhill & Vidrine 2002). Najadicola ingens inhabits different species of bivalve mussels Unionidae (Humes & Russell 1951;Humes & Jamnback 1950;Simmons & Smith 1984;Edwards & Vidrine 2013;Vidrine & Lieux 1980).…”

Nine new species in the subgenusAtacella(Acari: Unionicolidae:Unionicola) from Mexico and Brazil

“…Terminology for adult structures follows that used by Simmons and Smith (1984). Measurements are expressed in microns and in the format, mean (range).…”