Bioaccumulation of Waterborne and Dietary Cadmium by Oval Squid, Sepioteuthis lessoniana, and its Distribution Among Organs

Bioaccumulation of cadmium (Cd) by oval squid, Sepioteuthis lessoniana, the relative contributions of Cd in water and food to bioaccumulation, and the distribution of cadmium among organs were studied. In a bioconcentration test, oval squid was exposed to 0.2 mg Cd/l seawater for 14 days, then was reared in Cd-free seawater for 14 days. After the exposure and elimination periods, the Cd concentrations in the whole body were 3.10 ± 0.18 and 1.90 ± 0.05 μg/g wet weight (ww), respectively. The bioconcentration factor (BCF) was 15.5 after exposure for 14 days. The liver exhibited the highest Cd concentration (49.3 μg/g ww), and had the highest proportion of organ Cd content (42.8%) to whole-body burden at the end of the exposure period. In a biomagnification test, oval squid was exposed to 0.12 mg Cd/l seawater for 15 days and was simultaneously fed mummichog, Fundulus heteroclitus, that were simultaneously exposed to the same Cd concentration. For a further eight days the squid was kept in Cd-free seawater and was fed mummichog that were also kept in Cd-free seawater. After the exposure and elimination periods, the Cd concentrations in the whole body were 4.18 ± 0.69 and 2.80 ± 0.44 μg/g ww, respectively. The concentration of whole-body Cd in the oval squid that was derived from water was estimated at 1.86 μg/g ww after calculation of a BCF from the bioconcentration test. The contribution of Cd derived from water to the whole-body Cd burden appeared similar to that of the Cd derived from food. In the biomagnification test, the liver Cd concentration (58.8 μg/g ww) and its proportion of the whole-body Cd concentration (40.6%) were the highest among those of all the organs after exposure for 15 days, regardless of the uptake route. Because wild squid seem to be exposed to much lower Cd concentrations in water and are subjected to similar Cd concentrations in their prey, compared with squid of the present study, the main Cd source for squid would appear to be dietary.