74
in function, energy requirements and metabolic chemistry.
It
was required that the tissue have a high specific requirement
for zine and a fairly steady rate of metabolism.
The tissues
examined from the 1958 fish collections were all,
in some way,
unsatisfactory.
Stomach and liver have a high specific
requirement for zine which is a component of enzymes involved
in the regulation of acid-base equilibrium and in digestive
processes in these organs
(Vallee,
1957).
They are not,
how~-
ever entirely satisfactory because of the variability of zinc
requirements stemming from periodic metabolic activity changes
linked to feeding.
Gonad tissue is also unsatisfactory due to
the periodicity which characterizes its metabolism.
Gills,
due
to the tendency of particulate matter from the water to stick
to the gill filaments,
are also unsatisfactory.
Muscle and
bone maintain a fairly steady rate of metabolism, but are not
entirely satisfactory due to their low zine levels.
on the other hand,
Leiner
The eyes,
sgeem to fulfill the basic requirements.
(1943) reported concentrations of zinc in the retina of
the eyes of bony fishes at least three times as great as in
other tissues.
The acid-base equilibrium of the vitreous humor
is regulated by the ubiquitous zinc enzyme,
(Maetz,
carbonic anhydrase
1956), and an essential step in the chemistry of the
visual process is catalyzed by the retinal enzyme,
retinene