Distribution of Ingested Zinc-65 in the Tissues of Some Marine Crustaceans

Abstract

Autoradiographs of tissues of euphausiids and shrimps fed ⁶⁵Zn through a food chain showed the isotope located primarily in the interstitial spaces between muscle fibers, in the eye mainly between the rhabdoms and crystalline cones of adjacent ommatidia, within the exoskeleton, and on the interior surface of the exoskeleton. Comparisons of the autoradiographic evidence with concentrations of radiozinc and stable zinc in the various dissected tissues were in good agreement. The specific areas of ⁶⁵Zn localization were much the same as those seen in an earlier study of similar organisms that accumulated ⁶⁵Zn directly from sea water; thus, it appears that ⁶⁵Zn, and therefore zinc, is highly labile in marine crustaceans and will accumulate in certain specific locations regardless of the mode of uptake. The rates at which various tissues became saturated with ⁶⁵Zn were dependent upon mode of uptake, however. Because most of the ⁶⁵Zn was located intercellularly, and not intracellularly, most ingested zinc apparently accumulates in excess of the animals' needs and is not used metabolically.