Assessment of Heavy Metal Toxicity in Four Species of Freshwater Ciliates (Spirotrichea:Ciliophora) from Delhi, India

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Influence of copper and cadmium toxicity on antioxidant enzyme activity in freshwater ciliates

694-701Though metals are biologically important, increase in the threshold concentration of heavy metal in the environment may interfere with the metabolic activity of organisms. Heavy metal stress induces production of reactive oxygen species (ROS) viz. hydroxyl radical, superoxide radical or hydrogen peroxide (H2O2). Various antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, glutathione peroxidase and peroxiredoxin of SOD-ascorbate-glutathione cycle get activated during such stress. These enzymes are involved in ROS detoxification , and thereby protect the cells from oxidative stress. In this study, we explored activity of the antioxidant enzyme, superoxide dismutase (SOD) in the presence of heavy metals i.e., Cu and Cd in three freshwater ciliates, Tetmemena sp., Notohymena sp. and Euplotes sp. Heavy metals negatively affected the population growth of chosen ciliates which was measured as 24 h-LC50. The 24 h-LC50 doses of Cu and Cd, respectively were 0.14 and 2.44 mg/L for Tetmemena sp.; 0.74 and 5.06 mg/L for Notohymena sp.; and 0.17 and 2.24 mg/L for Euplotes sp. The levels of SOD were found to be significantly higher in the presence of Cu and Cd. Interestingly, exposure with Cu increased the SOD level at LC30 and LC50 doses, however, at higher concentration of Cu (i.e., LC70 dose), SOD level decreased. The results suggest that SOD may be used as an effective enzymatic biomarker to evaluate the toxic effects of heavy metals in the ciliate species

Morphology and morphogenesis of a new oxytrichid ciliate, Notohymena limus n. sp. (Ciliophora, Oxytrichidae) from Delhi, India

The morphology and morphogenesis of a new oxytrichid ciliate, Notohymena limus n. sp. were studied in vivo and after protargol impregnation. The new ciliate was isolated from the sewage sludge at Delhi Jal Board Sewage Treatment Plant located at Rithala, Delhi, India, using the non-flooded Petri dish method. N. limus n. sp. is characterized as follows: flexible dorsoventrally flattened ellipsoidal body; Notohymena-pattern undulating membranes; adoral zone of membranelles (AZM) occupied about 39% of the body length, and consists of around 26 membranelles; large and deep buccal cavity; colorless subpellicular granules present in groups and arranged around the bases of dorsal bristles; 4 macronuclear nodules; 2 micronuclei; 18 fronto-ventral-transverse (FVT) cirri in typical Oxytricha-pattern; 6 dorsal rows of bristles; 3 caudal cirri; about 16 right and 15 left marginal cirri; N. limus n. sp. is a new species on the basis of the combination of morphological, morphometric and morphogenetic characteristic features. Keywords: Morphology, Morphogenesis, Notohymena, Oxytrichida