The histopathology of infection by Lepeophtheirus pectoralis (Müller) (Copepoda: Caligidae)

The histology of the pectoral fin of the flounder, Platichthys flesus. (L.), is described and the presence of eosinophilic granule cells in the epidermis was noted. The histopathological effects of infection by L. pectoralis result from the attachment and feeding activity of the parasite. Although the damage inflicted by L. pectoralis is usually confined to the epidermis the lesions caused by sessile life cycle stages, adult females and chalimus larvae, often extend into the dermis. In the dermis the inflammatory response comprised fibroplasia and cellular infiltration which resulted in the formation of a dense fibrous granulation tissue.