Post-exposure feeding and motionless may be useful endpoints for assessing toxicity. The present study aimed to examine (i) the immobility of the estuarine snail Hydrobia ulvae resulting from short-term exposure to copper-spiked sediment, and subsequently, (ii) the potential application of post-exposure feeding (indirectly measured as pellets excreted) as an ecotoxicological response associated with motionlessness. Mobility and post-exposure feeding were influenced by copper contamination. Motionless was noticeable above the concentration of 200 µg Cu g -1 , where 40% of the organisms were inactive. Practically all the organisms remained active at the two lowest concentrations: 40 (control) and 60 µg Cu g -1 . For 400 and 800 µg Cu g -1 the motionless was generally higher than 50%. Mortality higher than 25% was observed at 200, 400 and 800 µg Cu g -1 , with values of 27, 40 and 60%, respectively. The feeding inhibition values showed an increasing inhibition from 20% at the lowest concentration (60 µg Cu g -1 ), up to 59% at 400 µg Cu g -1 ; at concentration of 800 µg Cu g -1 , although the physical activity inhibition had reached 67%, the post-exposure feeding was 1.5 higher in relation to the control. Probably, the starvation period due to motionless during exposure seems to increase the post-exposure feeding and egestion when food was provided; alternatively, increased pellet production could also indicate a detoxification process.

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