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Simple Summary: Simple Summary: Water mites are a significant population of Arachnida in aquatic ecosystems, with over 7500 species described worldwide. The genus Unionicola, belonging to the family Unionicolidae, is known for its parasitic behavior, often consuming the mucus and tissue of its molluscan hosts. While most species in this genus parasitize mussels, some have been found in gastropods. In our study, we discovered water mites infesting two species of gastropods: Filopaludina sumatrensis polygramma and F. martensi martensi. Through a comparison with known species, we identified this mite as a new species within the genus Unionicola, subgenus Polyatax, and named it "Unionicola (Polyatax) kasetbangkhenensis sp. nov.". Two species of gastropods, Filopaludina sumatrensis polygramma and F. martensi martensi, were found infested with water mites of the genus Unionicola in Bangkok and Nonthaburi provinces, Thailand. Morphological studies on these water mites, based on the characteristics of their genital acetabular and female genital fields, identified them as a new member of subgenus Polyatax. Unionicola (Polyatax) kasetbangkhenensis sp. nov. was named after the first location where this parasitic water mite was discovered. This species is distinguished from others by the pattern of their female genital field, with their anterior acetabular plates each bearing two acetabula and a short thick spine on the inner margin. Additionally, it differs from other species by the structure of the spines in its pedipalps and legs, as well as in the shapes of its coxal plates. [ABSTRACT FROM AUTHOR]

Five species of Unionicola Haldeman, 1842 (Acari: Hydrachnidia: Unionicolidae) were collected between 2018 and 2019. Notably, Unionicola (Armatax) armata Walter, 1929, previously unrecorded in China, is now documented for the first time in the country. Additionally, Unionicola newsumi Wiles, 1999 has been reclassified and assigned to the new subgenus Vespicola within the genus Unionicola Haldeman, 1842. These findings also led to the establishment of three new subgenera: Micronodusgen. nov., Vespicolagen. nov., and Lingshuiataxgen. nov. including four species: Unionicola soluplatussp. nov. U. jinisp. nov. U. caudipessp. nov. and U. armatallasp. nov. This marks the first description and documentation of these subgenera and species. [ABSTRACT FROM AUTHOR]

Two species of gastropods, Filopaludina sumatrensis polygramma and F. martensi martensi, were found infested with water mites of the genus Unionicola in Bangkok and Nonthaburi provinces, Thailand. Morphological studies on these water mites, based on the characteristics of their genital acetabular and female genital fields, identified them as a new member of subgenus Polyatax. Unionicola (Polyatax) kasetbangkhenensis sp. nov. was named after the first location where this parasitic water mite was discovered. This species is distinguished from others by the pattern of their female genital field, with their anterior acetabular plates each bearing two acetabula and a short thick spine on the inner margin. Additionally, it differs from other species by the structure of the spines in its pedipalps and legs, as well as in the shapes of its coxal plates.

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.) trapezidenssp. 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. [ABSTRACT FROM AUTHOR]

Multiparasitism by different species of larval water mites was observed on an adult midge collected in Hokkaido, northern Japan. Water mite larvae of Hygrobates sp. and Unionicola sp. in an inactive stage were discovered from a single chironomid female in the subfamily Chironominae. Eight Hygrobates larvae parasitized on the dorsum, and four were on the venter from the first to fourth abdominal segments of the midge. One Unionicola larvae attached on the trochanter of the left midleg and one on the femur of the right midleg. Their attachment sites on the midge accorded well with the larval site preferences of these two genera, as reported in past studies. Considering the preference of Unionicola for the specific segments of the legs, the observed site partitioning between Hygrobates and Unionicola seems to have originated by intrinsic site preferences of each taxon rather than interspecific competition. On the other hand, two less-engorged Hygrobates larvae were observed among the fully engorged larvae on the abdominal segments of the midge. Such developmental variations are possibly caused by intraspecific competition for nutrients among conspecific larvae on a single host individual. [ABSTRACT FROM AUTHOR]

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.) trapezidenssp. 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.