Aurelia polyps and ephyrae were exposed to microgravity for nine days as part of the SLS-1 mission. This experiment was to study the effects of microgravity on: the development of ephyrae from polyps; the development of the graviceptors (rhopalia) of ephyrae; the formation or demineralization of statoliths of rhopalia; and the swimming/pulsing behavior of ephyrae.



++ -- View more Approach: Polyps were induced to strobilate at 28°C, using iodine or thyroxine, at forty-eight (L-48h) and twenty-four (L-24h) hours before launch, and eight hours after lift-off (L+8h). Some ephyrae that formed in space were fixed in space on mission day eight, while others were fixed postflight. Postflight, light, and electron scanning microscope examinations were performed. Results: The number of ephyrae formed per polyp were slightly higher in the L+8h groups as compared to those induced at L-24h and L-48h. On Earth, iodine is used by jellyfish to synthesize jellyfish-thyroxine (Jf-T4), which is necessary for ephyra production. Since iodine-treated polyps gave rise to ephyrae in space it appears that jellyfish are able to synthesize Jf-T4 in space. The two groups of polyps not given the inducer still formed ephyrae in space presumably due to enhanced Jf-T4 synthesis, utilization, or accumulation. Morphologically, ephyrae which developed in space were very similar to those that developed on Earth. Quantitation of arm numbers revealed that there were no significant differences between space and Earth-developed ephyrae. Pulsing abnormalities, however, were found in greater numbers (18.3%) than in Earth-developed controls (2.9%). These abnormalities suggest abnormal development of the graviceptors, the neuromuscular system, or a defect in the integration between systems in these microgravity-sensitive animals.