Impact of Certain Heavy Metals on Histology and Physiology of Fishes: Interpretative Study

Heavy metals, as essential or non-essential ones, are present in aquatic systems at different levels. The over limited concentration of metals has a negative effects as physiological, histological and morphological patterns. The levels of contaminants in fish are of particular interest because of potential risk to human consuming them. Heavy metals bring about their effects as single or mixture on organs or tissues of fish. The influence starts at cellular or molecular level, then being at population level, particularly through early stages of development, and may result in species extinction, due to tendency towards accumulation and reduced biodegradation. The liver, gills and kidney seem to be the most interested organs included in current studies due to their sensitized feature towards metal impact. Fishes could be employed as biomarker indicator for environmental contamination, in particular with long term monitoring, and with trace levels of pollutants. Overlap between different factors, along with integrated responses must be considered in determination of heavy metals impact, in complementary of water quality parameters; and so, standardized methods being necessary for comparison among variable results obtained. This study is an interpretative effort of some aspects included in toxicity of five heavy metals for fish species.