2003 Volume 20 Issue 2 Pages 51-54
The effects of light condition on strobilation of Aurelia aurita polyps were investigated in the laboratory. Significant differences in changes in the cumulative proportion of strobilae among total polyps were found between polyps incubated under light and dark conditions. Under dark conditions 94.8% of polyps strobilated during 65 days of incubation experiment, but only 30% did so under light conditions. Polyps incubated under dark conditions liberated, on average, eight times more ephyrae by strobilation than polyps incubated under light conditions. Increased strobilation in the dark may be an adaptive behavior for polyps since strobilation in nature occurs during the winter, when light intensity is low. It is likely that highly eutrophicated waters such as Tokyo Bay will contribute to the asexual reproduction of polyps due to the blocking of light and a concomitant in ephyra populations.