Thyroxine in Early Strobilation inAurelia aurita

Abstract

Radiochromatographic studies of 131I-treated Aurelia polyps revealed synthesis of three compounds tentatively identified as monoiodotyrosine (MIT), diiodotyrosine (DIT), and thyroxine (T4). One compound, MIT, is found within 8 hr after 131I administration, before the detection of DIT or T4 which appear within 24 hr. T4 is not usually detected after 48 hr although MIT and DIT were found up to the segmentation period. None of the compounds were detected in ephyrae treated with 131I for 24 hr. Administration of low dosages of the goitrogens, thiourea,, propylthiouracil, and potassium thiocyanate, in conjunction with iodide, prevented strobilation induction. Radiochromatography of jellyfish given the goitrogens and 131I revealed a reduced uptake of iodide and an impairment of the synthesis of the iodinated compounds. Jellyfish use thyroxine directly for strobilatioa induction as demonstrated by 131I - labeled T4 administration. The T4 was detected in the polyps up to the 48-hr period of strobilation during which time some of the T4 was excreted into the medium, as was some 131I. The fact that T4, synthesis has thus far been found only in strobilating forms of Aurelia suggests that T4 is involved primarily with the differentiation of new structures which occurs during strobilation.