Iodine induction of metamorphosis in Aurelia

Abstract

Abstract Extensive laboratory investigations revealed two factors of primary importance for the initiation of metamorphosis (strobilation) in Aurelia aurita. It was found that sufficient quantities of iodide ions (in the form of either potassium iodide or elemental iodine) must be present for scyphistomae preconditioned at a low temperature to strobilate. The iodide ion requirement represents a very low dosage (1: 10 8 dilution). Thyroxin, also in very minute quantities, likewise induces strobilation in temperature‐preconditioned Aurelia. This response to thyroxin represents the first clearcut demonstration of a morphogenetic response of a coelenterate to a hormone which is biologically significant in vertebrates. A recommended temperature for preconditioning this Texas strain of Aurelia to strobilate is 19° for at least one month prior to testing. Organisms maintained at 27°C can be induced to strobilate for several months, but they ultimately lose their ability to respond to induction stimuli. A higher test temperature of 27°C does, however, hasten the strobilation of scyphistomae in iodine‐containing media. Other environmental factors i.e., nutrition, and pH and hypotonicity of the medium, were found to be of little importance (within limits) to the mechanisms involved in the induction of strobilation (SI) in these organisms.