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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI:

    Scaphanocephalus-associated dermatitis as the basis for black spot disease in Acanthuridae of St. Kitts, West Indies

    Michelle M. Dennis*, Adrien Izquierdo, Anne Conan, Kelsey Johnson, Solenne Giardi, Paul Frye, Mark A. Freeman

    *Corresponding author:

    ABSTRACT: Acanthurus spp. of St. Kitts and other Caribbean islands, including ocean surgeonfish A. bahianus, doctorfish A. chirurgus, and blue tang A. coeruleus, frequently show multifocal cutaneous pigmentation. Initial reports in the Leeward Antilles raised suspicion for a parasitic etiology. The aim of this study was to quantify the prevalence of the disease in St. Kitts’ Acanthuridae and describe its pathology and etiology. Visual surveys demonstrated consistently high adjusted mean prevalence at three shallow reefs in St. Kitts in 2017 (38.9%, 95%CI: 33.8–43.9) and 2018 (51.5%; 95%CI: 46.2–56.9). There were no differences in prevalence across species or reefs, but juvenile fish were less commonly affected than adults. Twenty-nine dermatopathy-affected acanthurids were sampled by spearfishing for comprehensive postmortem examination. Digenean metacercariae were dissected from <1 mm cysts within pigmented lesions. Using partial 28S rDNA sequence data they were classified as Family Heterophyidae, whose members are commonly implicated in black spot disease of other fishes. Morphological features of the parasite were most typical of Scaphanocephalus spp. (Creplin, 1842), and two genetic profiles were obtained suggesting more than one digenean species. Histologically, pigmented lesions had mild chronic perivascular dermatitis and increased melanophores and melanin density, often centered on encysted digenean metacercariae. In one affected A. chirurgus, similar metacercariae were histologically identified in skeletal and cardiac muscle. Further research is needed to clarify impact on host fitness, establish the number of heterophyid digenean species that cause black spots on Caribbean fishes and to determine the intermediate and definitive host species.