Portland State University. Department of Biology
James R. Pratt
Term of Graduation
Date of Publication
Master of Science (M.S.) in Biology
Ciliata, Toxicity testing
1 online resource (vii, 56 pages)
Standard toxicity tests often require high costs for maintaining healthy cultures, so few test species are employed in routine ecotoxicological analysis. An alternative is the "battery of tests" approach involving using rapid toxicity tests for screening. Rapid-screening toxicity tests must display organism sensitivity, similarity in responses to other test organisms, relevancy to many circumstances, and repeatability. Protozoa are ideal candidates for rapid-screening bioassays. They are cosmopolitan, play important roles in ecosystems, and have high reproductive rates. Many protozoa can form a resting stage (cyst) that remains viable during adverse conditions, eliminating the need for maintaining continuous cultures for testing.
The main objective of this research was to evaluate the soil ciliate, Colpoda inflata (Stokes), as a bioassay organism in rapid-screening tests by determining its sensitivity to a variety of model compounds. These tests were based on the principle that exposure to a toxic compound would negatively affect population growth. To test for sensitivity, C. inflata was exposed to different levels of dissolved organic carbon in test media for each compound tested. C. inflata was expected to be more sensitive to toxicants in an inorganic medium than in media with high organic carbon content. Data were analyzed by determining the median tolerance limit for inhibition of population growth (IG50) relative to controls. IG50 values of the eight model compounds tested varied considerably. C. inflata growth was not significantly affected by 2,4-D or malathion. C. inflata showed differences in sensitivity between organic and inorganic media for the toxic metals tested and the order of toxicity corresponded to those found in standard tests. A significant difference occurred between the test media and the pesticide PCP, where growth was not inhibited in the organic medium; in the inorganic medium the IG50 was 0.269 mg/L. No significant effect of test media was found for ammonia or SDS. Compared to several published toxicity results, C. inflata proved more sensitive overall than other rapid-screening tests and many standard acute toxicity tests. Results of this study show that this rapid-screening toxicity test is sensitive, repeatable, and provides information similar to traditional standard toxicity tests.
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Mochan, Daria Galina, "Evaluation of a Rapid-screening Toxicity Test Using the Ciliate, Colpoda inflata (Stokes): Sensitivity and Bioavailability to Model Compounds" (1996). Dissertations and Theses. Paper 5165.