EFFECTS OF THYROXINE AND THIOUREA ON THE EARLY DEVELOPMENT OF CHUM SALMON (ONCORHYNCHUS KETA)

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Abstract
Eggs of chum salmon were incubated in solutions of synthetic thyroxine sodium or thiourea. Thyroxine accelerated growth of the body wall and pectoral fins but reduced the rate of increase in body length. In addition, thyroxine treatment produced exophthalmia, intense deposition of guanine, and decreased pigmentation. Thiourea likewise reduced the rate of growth in length but had no apparent effect on the development of body wall or fins. Decreased deposition of guanine was evident in thiourea treated fish but the deposition of melanin was not affected. Thyroids of fish treated with thyroxine showed characteristic colloid storage while those of fish in thiourea were hyperplastic. The rate of contraction of the embryonic heart was unaffected by the treatments.