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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03673

    Development of a semi-quantitative scoring protocol for gill lesion assessment in greenlip abalone Haliotis laevigata held at elevated water temperature

    R. L. Pedler, J. O. Harris*, N. L. Thomson, J. J. Buss, D. A. J. Stone, J. H. Handlinger

    *Corresponding author:

    ABSTRACT: Water temperatures that exceed thermal optimal ranges (~19-22°C for greenlip abalone Haliotis laevigata, depending on stock genetics) can be associated with abalone mortalities. We assessed histopathological changes in H. laevigata gills held in control (22°C) or elevated (25°C) water temperature conditions for 47 d by developing a new scoring protocol that incorporates histopathological descriptions and relative score summary. Lesions were allocated to one of 3 reaction patterns, (1) epithelial, (2) circulatory or (3) inflammatory, and scored based on their prevalence in gill leaflets. Indices for each reaction pattern were calculated and combined to provide an overall gill index. Haliotis laevigata held in 25°C water temperature had significantly more epithelial lifting and hemolymph channel enlargement and significantly higher gill and circulatory reaction pattern indices than H. laevigata held in 22°C water temperature. One H. laevigata had proliferation of un-identified cells in the v-shaped skeletal rod of a gill leaflet. The un-identified cells contained enlarged nuclei, a greater nucleus-cytoplasm ratio and in some cases, mitotic figures. This cell population could represent a region of haematopoiesis in response to hemocyte loss or migration to a lesion. Without thorough diagnostic testing, the origin of these larger cells cannot be confirmed. The new scoring protocol developed will allow the standard quantification of gill lesions for H. laevigata, specifically for heat-related conditions, and could further be adapted for other Haliotis spp..