Exaiptasia pallida has been applied as a cnidarian model to assess the toxicity of various contaminants using endpoints related to growth, reproduction and mortality. However, increasingly accepted behavioural and biochemical endpoints are underrepresented in ecotoxicity testing with cnidarian species. The aim of this study was to assess the suitability of tentacle retraction and superoxide dismutase activity as behavioural and biochemical endpoints for ecotoxicity testing with E. pallida. A concentration-dependent, tentacle retraction response was found in sub-lethal toxicity testing for anemones exposed to 1-65 μg L-1 Cu and 2-630 μg L-1 Zn for 24 and 96 h. Semi-quantitative and quantitative approaches to tentacle retraction analysis showed a difference in response sensitivity, however, both methods resulted in similar 24- and 96-h EC50 values for Cu and Zn. Additionally, tentacle retraction analysis provided the benefit of identifying recovery in anemones previously exposed to 359 μg L-1 Zn following a 96-h recovery period. Conversely, no significant difference in superoxide dismutase activity was detected in anemones exposed to the Cu and Zn solutions compared with controls, after either 24- or 96-h exposures. These findings support the ease of application and sensitivity of tentacle retraction as an endpoint in ecotoxicity testing with E. pallida and recommend its suitability for use in acute, sub-lethal toxicity testing. Moreover, evidence of recovery in E. pallida following exposure suggests that recovery should be incorporated into future toxicity assessments.
Keywords: Copper; Hormesis; Recovery; Sub-lethal toxicity; Tropical marine ecotoxicology; Zinc.
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