Contents and chemical forms of arsenic in shellfishes in connection with their feeding habits.

Arsenic contents and its chemical forms in shellfishes were examined in connection with their feeding habits. The shellfishes used were 5 species of plankton-feeding bivalves, 3 species of herbivorous gastropods, and 7 species of carnivorous gastropods. The arsenic content (wet-weight basis) in soft tissue or muscle of bivalves and herbivorous gastropods was below 10 ppm in most specimens. In contrast, the arsenic content in muscle of carnivorous gastropods was significantly high; the mean values ranged from 16.8 ppm (Neptunea arthritica) to 67.9 ppm (Reishia bronni). The arsenic content in mid-gut gland was higher than that in the soft tissue or muscle in the cases of bivalves and herbivorous gastropods but lower in the case of carnivorous gastropods. Regardless of the species and tissues, the ratio of water-soluble organic arsenic to the total arsenic in soft tissue or muscle was somewhat lower in carnivorous gastropods than in the other two groups. These results suggested that carnivorous gastropods can be distinguished from bivalves and herbivorous gastropods with respects to arsenic contents and its chemical forms.