Embryonic development of the freshwater snail Biomphalaria glabrata under microgravity conditions (STS-89 mission)

The embryonic development of the fresh-water snail Biomphalaria glabrata was examined under microgravity-conditions and compared with the ground control and standard embryos, putting special emphasis on the shell formation. The process of shell formation may be particularly sensitive to the change of gravitational forces. The project aimed at determining whether the processes of mineralization during the formation of the exoskeleton in the growing snail embryo take place normally under microgravity conditions. Twenty-four adult individuals of the tropical freshwater snail B. glabrata were maintained 9 days in the Closed Equilibrated Biological Aquatic System (CEBAS Minimodule) on Space Shuttle flight STS-89. The animals produced spawning packs throughout the duration of the mission so that embryos of all developmental stages were achieved. The embryos developed slightly slower in the CEBAS than under standard conditions, and in older embryos a decreased mineralization of the shell was detected. These phenomena, however, were observed in the flight module as well as in the ground control specimens and was not an effect caused by the microgravity conditions. Embryos of B. glabrata showed a correct morphogenesis under microgravity, no teratological effects were noticed, and the shell formation proceeded normally.