Effects of Weightlessness of Aurelia Ephyra Differentiation and Statolith Synthesis

Aurelia polyps are especially suited for space flight experiments because they are very small (2 to 4 mm), form ephyrae with gravity sensing structures in 6 to 7 days, and can be reared easily and inexpensively in the laboratory. During iodine-induced metamorphosis ephyrae develop in sequential order from the oral to the aboral end of the polyps. Eight sites of gravity receptors (rhopalia) form per ephyra. These structures have sacs of statoliths at their distal end, which are composed of calcium sulfate dihydrate. Only one statolith forms per cell (statocyte) and the cells collect at the distal end of the rhopalia forming statocysts. Rhopalia with statocysts are necessary for the righting reflex of swimming medusae. Using the Aurelia Metamorphosis Test System (Spangenberg, 1984) for the past eight months, the effects of clinostat rotation in the horizontal and verticall planes on the development of ephyrae and the synthesis of their statoliths were investigated.