New Molecular-Based Phylogeny of Mussel-Associated Mites Reveals a New Subgenus and Three New Species Representing an Example of a Host-Driven Radiation in Indochina and Confirms the Concept of Division of the Genus Unionicola Haldeman, 1842 (Acari: Unionicolidae) into Numerous Subgenera

Abstract

Here we describe a new subgenus and three new species of parasitic water mites in the genus Unionicola (Acari: Hydrachnidia) from Myanmar: Myanmaratax subgen. nov., Unionicola (Myanmaratax) savadiensis subgen. and sp. nov. (hosts: Lamellidens savadiensis and L. generosus), U. (My.) generosa sp. nov. (the same hosts), and U. (My.) trapezidens sp. nov. (hosts: Trapezidens dolichorhynchus and T. angustior). These taxa were identified based on a two-gene phylogenetic analysis (COI + 28S), which also confirms the division of the genus Unionicola into numerous subgenera. The new species are cryptic species, which are morphologically indistinguishable but strongly resemble U. (Prasadatax) brandti Vidrine, 1985 described from Thailand (hosts: Lens spp. and Ensidens spp.). We also transfer the latter taxon from Prasadatax to Myanmaratax based on a set of morphological evidence and propose U. (My.) brandti comb. nov. The new subgenus contains a total of five species, one of which needs future sampling efforts and will be described elsewhere. Additionally, 56 valid subgenera, which were placed in the synonymy of the genus and in one case raised to the genus level, are restored here until robust phylogenetic evidence on their taxonomic status is available. Our results also confirm that Unionicola mites are narrow host specialists that are associated with either one or a few closely related freshwater mussel species belonging to one or two sister genera.

First record of Unionicola (Myanmaratax) savadiensis from India, with remarks on parasite-host relationship in unionicolid mites (Acari, Unionicolidae)

“…(M.) savadiensis (n=8), U. generosa (n=4), U. trapezidens (n=4), U. robacki (n=9), U. sella (n=2) and U. ypsilophora (n=1). COI sequence data were additionally taken from Chapurina et al (2021Chapurina et al ( , 2022a and Pešić et al (2021), and downloaded from the respective sequence data archives. Sequences were aligned with MUSCLE (Edgar 2004).…”

“…(Myanmaratax) brandti Vidrine, 1985 from the same host species. It is possible that the latter record was actually a mite belonging to one of the species described in the new subgenus in Chapurina et al (2022a), but lacking evidence supporting this, the record is considered doubtful. Chapurina et al (2022a, b) reported a number of species from Lamellidens Simpson, 1900 as gill mites from Myanmar, including U. diversipes, U.…”

“…In the Northern Hemisphere, it is not uncommon to find the representatives of both groups of mites in a single host individual, however, the mites apparently are highly specific as to not only as sites of oviposition but also as to their selection of host species. The water mite literature supporting these hypotheses was summarized in Vidrine (2013a, b, 2021), and Ernsting et al (2014), and more recently in Chapurina et al (2021Chapurina et al ( , 2022a. Discovery of species new to science as well as associations new to science are also not uncommon, however, each discovery is important and helps to qualify significant hypotheses in evolutionary ecology of the complex 200-million year history of mites and molluscs associations (Edwards and Vidrine 2020).…”

“…(Dimockatax) huangthayaensis (Chapurina et al, 2022b), U. (Myanmaratax) generosa Chapurina, Vidrine, Kondakov, Vikhrev & Bolotov, 2022(in Chapurina et al, 2022a and U. (Myanmaratax) savadiensis Chapurina, Vidrine, Kondakov, Vikhrev & Bolotov, 2022(in Chapurina et al, 2022a.…”

Aquatic Biodiversity: Evolution, Taxonomy and Conservation

“…Based on the obtained molecular data, the authors reconstructed the phylogeography for the genus Niphargus. Chapurina et al [5] describe a new subgenus and three new species of the parasitic water mites in the genus Unionicola from Myanmar, Southeastern Asia. The data obtained by the authors confirm that Unionicola mites are narrow host specialists that are associated with either one or a few closely related freshwater mussel species belonging to one or two sister genera.…”