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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03586

    Morphomolecular and pathological study of Scaphanocephalus sp. in new host Siganus argenteus in the Arabian Gulf

    Afaf Abdullah Mubark Al-Salem, Hanadi B. Baghdadi, Mahmoud A. Mahmoud*, Mustafa Ibrahim, Elsayed M. Bayoumy

    *Corresponding author:

    ABSTRACT: In this study, metacercariae of Scaphanocephalus parasite (Platyhelminthes: Heterophyidae) were found in Siganus argenteus (Forktail rabbitfish/ streamlined spinefoot) in the Arabian Gulf of Jubail province, Saudi Arabia. The findings constitute “new host and locality records”. Based on the number of black spots containing parasite cysts per fish, our study indicated that Siganus argenteus had high infection intensities of encysted metacercariae belonging to the genus Scaphanocephalus. Of the 3500 S. argenteus specimens, 800 (22.9%) showed multiple black cysts all over the body surface including the membranous parts of the fins, while none were seen on the internal organs. The prevalence of infection was highest in summer (8.8%). The excysted metacercariae were morphologically different from any of the previously identified Scaphanocephalus spp. Molecular analysis of rDNA showed 100% identity with an unnamed Scaphanocephalus sp. reported from Caribbean fish. Therefore, our findings may indicate a new species of this previously rarely recorded fish parasite. The histopathological examination revealed that the encysted parasites were restricted to the dermal layer of the skin and surrounded by melanophores and a fibrous connective tissue capsule; with focal myositis and Zenker’s necrosis in the underlying muscle tissue. The characteristic winged parasite was clearly observed within the cysts. The recording of high prevalence of Scaphanocephalus infection in siganid fish requires further epidemiological study.