Comparisons of some heavy metal contents among four herbivorous gastropod mollusks in the same family

Four species, Monodonta labio (Ishidatami in Japanese), Chlorostoma lischkei (Kubogai), Chlorostoma xanthostigma (Kumanokogai), and Omphalius pfeifferi (Bateira), classified in Trochidae, Archaeogastropoda, Mollusca, were collected form the same sea area and at the same time. Five heavy metals, copper, manganese, iron, zinc and cadmium in whole soft bodies were quantitatively determined, and the content unit was represented as ppm on a dry weight basis. There was no difference in the order of magnitude in each metal content in each species, i.e. the differences in metal contents were less than 10 times for all five metals within each species. However, there were some differences in the contents among the species and also among the metals. Copper contents in C. xanthostigma and O. pfeifferi were higher than those in M. labio and C. lischkei. Manganese contents were nearly similar to the four species one another. Iron contents in M. labio were highest compared to those of the other three species. Zinc contents of the other three were higher than that in M. labio. Cadmium contents in C. lischkei were higher than those of the other three species. Constituent rates, by percentage, of five metals as a whole in each species were as follows: the rate of copper was the lowest in M. labio; for manganese the rate was nearly equal to one another; for iron the highest was in M. labio; for zinc the lowest was found in M. labio; and for cadmium the highest value was found din C. lischkei. The rates calculated in the other species and the other metals were nearly similar to one another. It can be inferred that the differences in metal distribution in each species in the same family and under the same environment resulted from different ecological niches and different accumulation responses to heavy metals of the four gastropods