Authors

Discussion

 Eggs and adults of a digenetic trematode were found in close association with “dusky grouper dermatitis (DGD)” lesions affecting the wild population of dusky grouper Epinephelus marginatus in the coastal waters of Libya. Histological evaluation of lesions found gravid hermaphroditic digeneans (ca. 1,500-2,000 µm long), within dermal blood vessels. The digeneans, based on their morphology, were subsequently assigned to the Aporocotylidae Odhner, 1912 (Platyhelminthes: Trematoda). Eggs (ca. 20-37 µm long), with embryos at various stages of development, from homogenous embryos in utero to fully developed miracidia, were found located within the dermis and epidermis. Evidence suggests their passage through host tissues is facilitated by the host’s inflammatory response - migrating from the dermal blood vessels to the dermis and then the epidermis, whereon the miracidia hatch and are released into the external aquatic environment. Alternatively, eggs are conveyed with the natural turnover of epidermal cells. The host’s inflammatory process involves the recruitment of eosinophils to the sites of infection and their degranulation in close proximity to eggs situated within blood vessels. Although blood flukes are recorded from the blood vascular system of serranids (Epinephelinae), this is the first record of a aporocotylid digenean occupying the cutaneous blood vessels of a piscine host.