Enhanced stress resistance of dormant bdelloids (rotifera)

Dormant rotifers (Macrotrachela quadricornifera) were exposed to several stresses on ground, on stratospheric balloons and on Shuttle, and their resistance was recorded in terms of survival. On ground, active and dormant animals were exposed to temperature and gravity variations and to UV radiation. In all tests the dormant rotifers were significantly more resistant than the hydrated ones. On balloons, dormant animals were exposed during approx. 20-h-flight to stratospheric conditions such as vacuum broad temperature changes and radiation. Recovery was rather poor, but the result could not be ascribed to any particular factor, because effect of single factors could not be discriminated. On Shuttle, dormant rotifers were exposed to hypogravity and vibrations and their recovery was very similar to ground controls. On the whole, dormant animals were more resistant than active ones under lab conditions, but no experiment has been run exposing active and dormant rotifers to space conditions, so far.