Effects of exposure to copper oxide nanoparticles on histopathological and ultrastructural lesions of gills and mantle organs in freshwater bivalve Anodonta cygnea

Aim: In this study gill and mantle histopathological and ultrastructural changes of freshwater bivalve, Anodonta cygnea from Unionidae in exposure to sub-lethal concentrations of copper oxide nanoparticles for 14 days were investigated.
Forty numbers of A. cygnea (length: 11.5± 0.9 cm; weight: 84.5±6 g) were collected from Tajan River estuary, Sari, Mazandaran Province and after transferring to the laboratory were divided into two control and treated groups. Treated group were exposed to 25 ppm CuO nanoparticles for 14 days. Gill and mantle tissue sections of control and treated samples were taken in days 4, 9 and 14, and then prepared for light microscopy using hematoxylin and eosin (H & E) staining method. Samples were studied by scanning electron microscopy (SEM) after fixation, drying and preparation.
Light microscopy results showed significant histological alterations in all of studied organs of exposed bivalves compared to the controls. Changes were hyperplasia, hypoplasia, gill filaments shape and dimension changes and also haemolymph channels adema. Also increasing mucous cells number and external epithelium hyperplasia in mantle were observed. SEM analyses showed adverse destruction of gill filaments and blocking water channels in gill specimens, as well as, mantel necrosis and indentation.
according to obtained results, it can be concluded that short time exposure to nanoparticles may lead to noticeable changes evident in histological and ultrastructural internal organs of freshwater bivalve Anodonta cygnea.