The effect of copper and temperature on juveniles of the eurybathic brittle star Amphipholis squamata: exploring responses related to motility and the water vascular system

The limited availability of test organisms that represent tropical and deeper water environments is a significant concern when assessing the risk of contaminants in these environments. Amphipholis squamata (Delle Chiaje 1828) is a widely distributed brittle star with many phylogenetic clades reported from different latitudes, and it also occurs from the intertidal zone to a depth of ∼1300 m. In the present study, the effect of copper on four behavioural responses and mortality of A. squamata were quantified at four different temperatures including 25, 20, 15 and 10 °C. At 25 °C the four behavioural responses and mortality were relatively sensitive to copper, with 96 h EC₅₀ values of 25 (confidence interval 18–44), 24 (7–26), 32 (24–41), 29 (9–41) μg L⁻¹ for the measured ability to turn from the oral surface up to oral surface down, curling behaviour, tube foot movement, and tube foot retraction respectively. The average 96-h LC₅₀ value for copper at 25 °C was 46 μg L⁻¹. Some endpoints investigated showed significant effects of reduced temperature compared to the optimal temperature. These effects were enhanced with increasing copper concentrations and significant differences in copper toxicity between temperature treatments were most notable when measuring the ability to turn from the oral surface up to oral surface down where the EC₅₀ changed from 25 (18 to 44) to 6 (−18 to 14) μg L⁻¹ with a reduction of temperature from 25 to 15 °C. The results showed that A. squamata is relatively sensitive to copper and that further investigation into the effects of other stressors on these endpoints is warranted.