Multi-organ histological observations on juvenile Senegalese soles exposed to low concentrations of waterborne cadmium
A histopathological screening was performed on juvenile Senegalese soles exposed to environmentally realistic concentrations of waterborne Cd (0.5, 5 and 10 μg L(-1)) for 28 days. The severity and dissemination of histopathological changes were variable and limited to the kidney, liver, spleen, gills and skin goblet cells. Contradicting available literature that refers the liver as the most affected organ upon acute exposure and the kidney following chronic exposure, the liver was the most impacted organ (even at the lowest concentration), in a trend that could relate to the duration of exposure and Cd concentration. The most noticeable hepatic alterations related to inflammation, although hepatocellular alterations like lipidosis and eosinophilic foci also occurred. The trunk kidney of exposed fish endured moderate inflammation, apoptosis and necrosis, however, without a clear time-dependent effect. The spleen of fish subjected to the highest concentrations revealed diffuse necrotic foci accompanied by melanomacrophage intrusion. The gills, albeit the most important apical uptake organ of dissolved toxicants, sustained only moderate damage, from epithelial hyperplasia and pavement cell detachment to the potentially more severe chloride cell alterations. In the skin, an increase in goblet cell size occurred, most notoriously correlated to Cd concentration at earlier stages of exposure. The results show that a metal-naïve juvenile fish can endure deleterious effects when exposed to low, ecologically relevant, concentrations of a common toxic metal and that the pattern of Cd-induced histopathological alterations can be complex and linked to organ-specific responses and metal translocation within the organism.