Identification of a sensitive index during fish bioassay of  an azo dye methyl red (untreated and treated)

 

Shweta Sharma¹, Subhasini Sharma¹ and K.P. Sharma²

¹Department of Zoology, ²Department of Botany, University of Rajasthan, Jaipur-302 004, India

 

(Received: 16 October, 2004 ; Accepted: 28 April, 2005)

 

 

Abstract: Acute and chronic toxicity of methyl red (untreated) was examined on a freshwater fish Poecilia reticulata, using indices viz; mortality, reduction in RBC counts and their morphological abnormality (poikilocytosis and anisocytosis). Similar studies (acute toxicity) were also made in physicochemically and biologically treated methyl red. Data comparison of these four indices revealed poikilocytosis as the most sensitive index, since it measured higher toxicity of methyl red when fish mortality was either minimum at its low concentration (5 ppm) during both acute and chronic toxicity or even nil in the biologically treated 100 ppm methyl red, during acute toxicity. Mortality was next to poikilocytosis though it ranked 1^st at higher concentration of methyl red during acute toxicity. The reduction in RBC counts however, was found to be the most sensitive parameter only in case of prolonged exposure (4 weeks) to 5 ppm methyl red. Amongst the four indices used for quantifying toxicity; anisocytosis was found to be the least expressive. Based on these findings we recommend quantification of data on fish mortality and poikilocytosis during acute toxicity whereas reduction in RBC counts and poikilocytosis during chronic exposure to methyl red.   

 

Key words: Fish bioassay, Methyl red, Mortality, RBC counts, Poikilocytosis, Anisocytosis.

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