Histopathology of leech, Austrobdella bilobata Ingram, infestation on the yellowfin bream, Acanthopagrus australis (Günther), in northern New South Wales

Abstract. The histopathology of leech, Austrobdella bilobata , infestation on the upper palate and pelvic fin of the yellowfin bream, Acanthopagrus australis (Günther), is described. The feeding site was often haemorrhagic and swelling surrounded the attachment site. Histological examination revealed massive cellular infiltration (predominantly lymphocyte and macrophage) in the submucosa beneath the feeding and attachment sites. The latter also had a complete erosion of the integument beneath the parasite. Localized proliferation of connective tissue fibres and zones of necrosis and oedema were present in some cases.