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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03529

    Ellipsomyxa ariusi sp. nov. (Myxosporea: Ceratomyxidae), a new myxosporean infecting gallbladder of threadfin sea catfish Arius arius in India

    Archana Chandran*, P. U. Zacharia, T. V. Sathianandan, N. K. Sanil

    *Corresponding author:

    ABSTRACT: The present study describes a new species of myxosporean, Ellipsomyxa ariusi sp. nov. infecting the gallbladder of the threadfin sea catfish, Arius arius (Hamilton, 1822). E. ariusi sp. nov. is characterized by bivalvular, ellipsoid or elongate-oval myxospores with smooth spore valves and a straight suture, arranged at an angle to the longitudinal spore axis. Mature myxospores measured 10.1±0.8 μm in length, 6.8±0.5 μm in width and 7.7±0.7 μm in thickness. Polar capsules are equal in size, oval to pyriform in shape, positioned at an angle to the longitudinal myxospore axis and open in opposite directions. Polar capsules measured 2.8±0.3 μm in length and 2.5±0.4 μm in width; polar filaments formed 4–5 coils, and extended to 32.2±2.1 μm in length. Monosporic and disporic plasmodial stages attached to the wall of gallbladder. Molecular analysis of the type specimen generated a 1703 bp, partial SSU rDNA sequence (MN892546) which was identical to the isolates from three other localities. In phylogenetic analyses, genus Ellipsomyxa appeared monophyletic and the present myxosporean occupied an independent position in Maximum Likelihood and Bayesian Inference trees with 100%/ 1 bootstrap value. The overall prevalence of infection was 54.8% and multiway analysis of variance revealed that it varied significantly with location, year, season, sex and size of the fish host. Histopathological changes associated with E. ariusi sp. nov. infection included swelling, vacuolation and detachment of epithelial layer, reduced mucus production and altered consistency and colour of the bile. Based on the morphologic, morphometric and molecular differences with known species of Ellipsomyxa, and considering the differences in host and geographic locations, the present species is treated as new and the name Ellipsomyxa ariusi sp. nov. is proposed.