Diseases of the Chilean flounder, Paralichthys adspersus (Steindachner, 1867), as a biomarker of marine coastal pollution near the Itata River (Chile): Part II. Histopathological lesions.

This study evaluated the histopathological lesions of the Chilean flounder, Paralichthys adspersus, inhabiting the marine coastal area influenced by the Itata River (central Chile) in order to provide an environmental baseline given the plans to discharge effluents from a cellulose plant through a submarine pipe in the area. Flounder were also sampled at two reference sites over the course of 1 year. Pathological examinations and descriptions of histopathological lesions follow the ICES suggested protocol: internal and histopathological lesions, condition factor, and hepatosomatic and spleen indexes. The prevalence of fish with histopathological lesions differed significantly among sites. The flounder sampled in the Itata area were the most affected. Evaluation of histopathological lesions observed on the flounder caught in the Itata area revealed (i) 16 different types of histopathological lesions, (ii) a high prevalence of lesions in gills and epidermal and hepatic tissue, and (iii) a normal K factor and hepatosomatic index. Significant differences were found in epidermal hyperplasia (EH), chronic dermatitis, telangiectasis (TEL), localized edema in the base of lamellae (LE), fusion of secondary lamellae (FSL), foci of cellular alteration (FCA), melanomacrophagic centers (MMCs), and hemosiderin (HEM) lesions among sites and among sites by season of the year. Winter 2006 was the most affected. A seasonal analysis of histopathological lesions on flounder caught in the Itata area showed significant differences for EH, progressive focal invasion of muscle fibers (PFIMF), TEL, LE, FSL, lamellar bifurcation, hepatitis, FCA, MMCs, and HEM lesions between the sampled seasons of the year; flounder caught in winter 2006 had the highest prevalence of these lesions except for PFIMF, which was higher in winter 2007. These results are discussed in relation to the contents of inorganic and organic compounds in the water column and the contents of organic compounds in sediments of the subtidal environment in the Itata area.