Induction of Metallothionein in Dogwhelk Nucella lapillus during and after Exposure to Cadmium

Induction of metallothionein (MT) was investigated in a common biomonitor, the dogwhelk Nucella lapillus (shell length: 27.7 ± 1.4 mm; wet tissue weight: 667 ± 196 mg), during and after exposure to cadmium (Cd) under controlled laboratory conditions (10 ± 1°C and 34 ± 1‰ salinity). The dogwhelks were exposed to 500 μg Cd l^-1 (2.2% of 96 h LC₅₀) for 60 days and then placed into clean seawater for 110 days. MT concentration in whole animal increased during the exposure period, peaked at Day 70, and then declined gradually. Half-life of MT was ca. 40 days. MT concentration increased very significantly with increasing Cd concentration (r = 0.74, n = 24, P < 0.001). Nevertheless, Cd concentration increased throughout the period of exposure and while in clean seawater, leveling off only after Day 120, indicating that Cd concentration could not be regulated by N. lapillus. Throughout the study, MT and Cd concentrations in gills, Leiblein gland, kidney, digestive gland, and gonad tissues increased gradually. Highest concentrations of MT and Cd were found in the Leiblein gland. Measurement of MT induction in the Leiblein gland of N. lapillus may therefore prove useful as a sublethal biological response to Cd contamination.