Effects of exogenous thyroxine on statolith synthesis and resorption in Aurelia

Abstract

Aurelia ephyrae which were maintained in thyroxine during their metamorphosis from the polyp state and another group of ephyrae which were in thyroxine forfour and eight days of starvation, had significantly reduced numbers of statoliths as compared with control ephyrae in equimolar concentrations of iodine and in artificial sea water. We conclude, therefore, that thyroxine significantly affects the mineralization and demineralization of statocytes resulting in changes in statolith numbers.A mineralization role of thyroxine in other invertebrates has not been reported in spite of the fact that thyroxine and its precursors, monoiodotyrosine and diiodotyrosine, have been located in numerous invertebrates, particularly in mineralizing areas such as developing shells. On the other hand, an important role of thyroxine in mineralization and demineralization of bones and teeth of vertebrates including humans, has been known for some time. The specific role of thyroxine in affecting mineralization in vertebrates is not known, due perhaps to the presence of many other hormones and second messengers which also affect mineralization. The use of the relatively simple Aurelia statolith test systems and the exploration for other invertebrate mineralizing systems which respond to thyroxine will hopefully lead to a better understanding of the basic mechanisms of thyroxine action in mineralizing systems in the future. © 1984 by the American Society of Zoologists.