Shell lesions and associated fauna of the Omani abalone Haliotis mariae (Mollusca: Archaeogastropoda)

Context Interactions of the Omani abalone Haliotis mariae have remained virtually unexplored over the past three decades. Aim To describe the shell lesions, namely, brittle shells, blisters, brownish spots, and the interactions of associated fauna with H. mariae. Methods Cultured and wild abalones (n = 23) from Dhofar, Oman, were examined to search for associated fauna and abnormal shell conditions. Metazoans and bacteria identified were confirmed through the 18S rRNA or 16S rRNA. Key results Shell lesions harboured polychaetes, molluscs, barnacles and bacteria. Polychaetes Syllis sp. and Cirratulus sp., and the barnacle Balanus amphitrite were associated with brittle shells (43.4%). The borers Polydora sp. and Lithophaga sp. occurred in blisters (mean height 8 ± 2 mm), being observed in 21.7% of abalones. Bacteria including Vibrio alginolyticus were isolated from brownish spots on shell nacre. The generalised linear model showed no significant effects of abalone size or origin on metazoan load. Conclusions Brittle shells, blisters, and brownish spots are here reported first time in H. mariae, associated with different biological agents representing potential etiological factors for cultured and wild abalones. Abalone size had a comparable effect on metazoan load in wild and farmed populations. Implications Long-term symbiont monitoring is needed in farmed and wild abalone populations to evaluate their impact and enhance preparedness to prevent health threats and mitigate further diseases.