Taxonomic richness and host range of tropical Asian mussel‐associated mite assemblages (Acari: Unionicolidae) with a description of a new subgenus and species of parasitic mite from freshwater pearl mussels (Unionida: Margaritiferidae)

Morphological, ultrastructure and molecular characterization of Unionicola chelata (Acari: Hydrachnida: Unionicolidae) isolated from Bellamya bengalensis, West Bengal, India

Unionicola spp. is a parasitic aquatic mite known to infect freshwater aquatic organisms, especially the marine and freshwater molluscs and few species of sponges. Unionicola chelata (Acari: Hydrachnida: Unionicolidae) generally infect the freshwater bivalves of the Genus Unio sp. They are usually facultative in nature and can be parasitic at any stage of their life cycle. They cause damage to the gills of the host which harms their normal respiration process. The present work portraits the morphological characters, ultrastructure and DNA barcoding of its mitochondrial gene Cytochrome Oxidase I (COI)(mtCOI), and its taxonomic position was justified by obtaining a phylogenetic tree. The description regarding its morphological characters, ultrastructure and molecular characterization has been presented here. This paper holds the report of a parasitic aquatic mite Unionicola chelata for the first time from a gastropod molluscan host Bellamya bengalensis (Lamarck, 1882), from Diamond Harbour, South 24 Parganas, West Bengal, India.

Associations of mayfly larvae with Corbicula clams

Currently, the parasitic and endosymbiontic fauna of Corbicula clams remain poorly studied throughout their range. Here, using samples from the Mekong basin, we describe two Symbiocloeon species new to science: Symbiocloeon corbiculinus sp. nov. and Symbiocloeon laoensis sp. nov. Our results and a review of available published data indicate that freshwater bivalve-associated mayflies are narrow host specialists, being associated with one or a few closely related species of freshwater bivalves. The bivalve-associated mayfly larvae have several specific morphological traits compared with free-living species, which include a reduction of integument chitinization and a significant reduction of the surface structures on segments. An increase in area of the respiratory surface of larval tergalia was also recorded. The possible positive and negative effects of mayflies on the clam hosts are discussed. This study is an example of the many possible hidden associations between aquatic species that remain to be described.

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

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.