-4gDiscussion
Te physiological roles of manganese, iron, cobalt, and
zine in plants and animals are not completely understood.
How-
ever, these elements participate in many enzyme reactions and
along with other elements have been conclusively demonstrated
to be nutritionally essential to, and incorporated into, higher
animals including humans (Underwood, 1956).
In the present work, detailed studies have been done on
Clam kidney and fish livers.
Although the accumulation of the
non-fissgion products is a process common to both animals, the
concentration patterns for the different isotopes are not the
same.
These differences are to be expected between various
phyla, and even between species within one phyla in which diffefent metabolic patterns or food habits occur,
In the fish livers Zn°> amounted to 35-58% of the total
activity but in the clam kidney this isotope was not present.
On the other hand, the absolute levels of radioactive iron, cobalt, and manganese were much higher in the clam kidney than in
the fish livers.
Te presence of large amounts of heavy metals in the clam
kidney is in agreement with the observations of members of this
Laboratory that the clam kidney has a remarkably high specific
gravity in comparison to soft tissues of other animals.
This
high specific gravity is reflected in the relation of ash weight
to wet weight in the present experiments.
In the clam kidney the
ash fraction accounted for 13% of the wet weight, but in fish
livers the ash accounted for only 2.6-2.9% of the wet weight.