we next carried out pre-hoc controlled laboratory experiments to test the effects of heavy metal pollution ( hg , zn , cd ) on genotypic frequencies of 15 phosphoglucomutase ( pgm ) genotypes in thousands of individuals of the shrimp palaemon elegans [ nevo et al , 1980 , 1981a , and the present study ] .
C0347988
heavy metal
C0025424
hg