Published online by Cambridge University Press: 09 October 2019
Juvenile mussels (Mytilus edulis, Mollusca: Bivalvia) were subjected to a simple assay to investigate the pattern and timing of the shift from high copper resistance of the veliger larva to the lower resistance of the adult. The level of resistance found in veligers persists in mussels of 1 mm shell length (400 ppb Cu; LT50, 12.5 d) while the lower adult level of resistance is reached at a shell length of 5 mm (400 ppb Cu; LT50 2.8–5.3 d). Resistance declines gradually, being significantly correlated with shell length (P<0.02) such that size differences explain 88% of the variation in copper resistance among juvenile mussels.