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A comparative study of iodine metabolism in juvenile Oncorhynchus Eales, John Geoffrey

Abstract

Comparative histological and radiochemical studies of iodine metabolism in juvenile Oncorhynchus revealed good agreement between thyroid epithelial height and ability to convert I¹³¹ into protein-bound I¹³¹(PBI¹³¹). The ratio of I¹³¹ to PBl¹³¹ in plasma samples (Conversion Ratio) was considered superior to other thyroid assays reviewed. Peaks in thyroid activity and loss of I¹³¹ from the body occurred in sockeye and coho at the time of downstream migration, but in chum and pink only when postmigrants were retained in fresh water. In coho and sockeye these changes were transitory, in chum irreversible and in pink prolonged. On the above basis, thyroxine was assigned no specific role but a theory of smolt evolution was proposed and related to a phylogeny within the genus Oncorhynchus.

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