ACUTE TOXICITY BIOASSAY AND BEHAVIOURAL CHANGES ON ZEBRA FISH, Danio rerio (Hamilton) UNDER ARSENIC TRIOXIDE

Arsenic, an important environmental contaminant, is present in the aquatic environment as a result of geogenic and anthropogenic processes (Gonzaliz et al., 2006; Singh and Banerjee, 2008) and it has been reported as one of the most alarming chemical (ATSDR, 2002). In the environment, arsenic is present in different forms and the toxicity depends upon its chemical form and oxidation states (Agusa et al., 2008). The toxicity of arsenical in animals depends on species, sex, age, exposure dose, duration of exposure, organic or inorganic form, valence state, etc., (Luh et al., 1973 and Allen et al., 2004). In natural water, arsenic is mostly exist in inorganic and organic form (Luh et al., 1973) and the inorganic form has been found to be more toxic (Liao et al., 2004). In the aquatic environment, the semimetal arsenic exists either in arsenite (the trivalent form, As 3+ ) or arsenate (the pentavalent form, As 5+ ), which are inter-converted through redox and methylation reaction (Reuther, 1992; Bears et al., 2006). Trivalent arsenic (As 3+ ) is more toxic than pentavalent arsenic (As 5+ ) (Bertelero et al., 1981; Liao et al., 2004). Among the various arsenical compounds, arsenic trioxide (As2 O3) is mostly used in synthesis of various inorganic and organic compounds and in agricultural chemicals. It is also used as a chemotherapeutic agent for the treatment of hematological malignancies (List, 2002). Arsenic trioxide (As2O3) was a dominant species in most of the arsenic contaminated area in India and which is almost 50% of the total area arsenic level (Chatterjee et al., 1993). The contamination of aquatic ecosystem by arsenicals and their impact on the aquatic organisms has now emerged as a serious environmental problem (Allen et al., 2004).