author(s)
Kshama Dwivedi and Sangeeta Singh

abstract
Arsenic (As) is a hazardous contaminant in the aquatic world, existing in inorganic and organic forms. Of inorganic forms arsenic exists as arsenite and arsenate in aquatic bodies like oceans, sea, rivers, lakes, ponds, and groundwater. In oxygenated water, trivalent arsenite is easily oxidized to arsenate. Arsenic being, most common heavy metal pollutant in fresh water, comes from mining, smelting, chemical manufacturing, and other anthropogenic sources. Due to release of acid mine drainage in the aquatic bodies, the pH falls and increasing metal solubility causes devastating effects to the aquatic organism. Arsenic gets locked up in the bottom sediments for many years causing damage to aquatic life and fishes. Generally ionic forms of a heavy metals are more toxic because it can form toxic compounds with other ions. Electron transfer reactions connected oxygen can form toxic oxyradicals. Some anions such as oxyradicals (O2-) and the hydroxyradicals (OH-) can cause serious cellular anionic damage. Ionic forms of arsenic are readily available to fish, resulting in considerable amount of metal accumulation in fish tissue, those living in polluted water. Relationship between the metal accumulation in fish organs and in water has been studied in field and laboratory both. The present paper reviews, the toxicological effects, and histopathological alterations due to arsenic on the important organs of fishes, like liver, kidney, gills, skin, muscles, bones, heart, and brain.