We investigated the effects of altered gravity on the life cycle of Dictyostelium discoideum after and during life-long exposure to one of three altered gravity (g) environments: (1) substrate inverted, parallel to and facing the surface of the Earth; (2) hyper-g; (3) reduced-g. To this end, we measured the height of the final stage of the life cycle, the mature spore-bearing sorocarp. Typically, the sorocarp stands erect and perpendicular to the substrate. In the case of each altered g environment, the control cultures were produced and treated identically to the experimental cultures except for the conditions of their exposure to altered g. Inverted cultures developing and growing in the same direction as the gravity vector had a mean height of 1.84 mm. Their counterpart control cultures had a mean height of 1.64 mm being therefore statistically significantly shorter. Cultures chronically exposed to a hyper (10) g environment produced sorocarps with a mean height of 1.13 mm. These were statistically significantly shorter than their 1 g controls whose mean height was 2.06 mm. Clinorotated (simulated reduced g) sorocarp heights (mean equal to 2.12 mm) were statistically significantly taller compared to their 1 g controls (mean equal to 1.79 mm). The significance level for all the statistical analyses is p < 0.05. Therefore, measurements of the mature stage after life-long exposure to simulated altered gravity show that the final height of the sorocarp is ultimately determined, at least partially, by the gravity environment in which development occurs.
