Copper toxicity to the endoparasitic trematode ( Posthodiplostomum minimum ) relative to physid snail and bluegill sunfish intermediate hosts

A laboratory study was conducted to determine copper toxicity to the endoparasitict ematode Posthodiplostomum minimum (MacCallum) relative to snail first intermediate hosts and bluegills ( Lepomis macrochirus Rafinesque) as second intermediate hosts. To determine copper effects on cercariae, the life‐cycle stages of P. minimum were established in the laboratory. A 96‐h median lethal concentration (LC50) test for bluegills was performed, and the calculated value of 0.892 mg/L total Cu was considered in selection of copper concentrations for all other experiments. Snail hosts ( Physella gyrina (Say)) exposed to copper concentrations equal to 0, 8.9, 22.3, 44.6, and 89.2 μg/L Cu, exhibited a significant toxic response with ∼64% and ∼87% mortality occurring in the 44.6 and 89.2 μg/L concentrations, respectively. The 7‐d LC50 for snails was 38.0 μg/L Cu. Free‐swimming cercariae exposed to the same copper concentrations exhibited a similar toxic response with a 9‐h LC50 of 32.0 μg/L Cu and a 12‐h LC50 of 26.0 μg/L Cu.