The effect of lodide and various lodocompounds on initiation of strobilation in Aurelia

Abstract

The effect of iodide and various iodocompounds on initiation of strobilation in Aurelia polyps was studied. Iodide was found to be active in initiating strobilation at concentrations between 10 −4 and 10 −7 M. The order of effectiveness of iodide, bromide and iodocompounds, tested at 10 −6 M concentrations, was (highest first): DIT, MIT, I −, T 3, T 4, Br −. The last had no effect. Results of experiments using different polyp concentrations indicated that strobilating polyps release a factor into the media that induces strobilation in other polyps. All agents shown to be active in initiating strobilation were tested in the presence of thiourea. At a concentration of 10 −4 M, thiourea completely inhibited the effect of all of the agents except DIT, which was only partially inhibited. New buds were found to be capable of strobilating only when tested in the presence of older polyps. None of the agents tested induced strobilation in new buds tested in the absence of older polyps. The data indicate that none of the iodocompounds tested is itself responsible for initiating strobilation and that each must be altered to be effective. Because its effect persisted in the presence of thiourea, DIT may be similar in the putative actual compound.