Very low (nano- and subnanomolar) concentrations of 10-(6′- plastoquinonyl) decyltriphenylphosphonium (SkQ1) were found to prolong lifespan of a fungus (Podospora anserina), a crustacean (Ceriodaphnia affinis), an insect (Drosophila melanogaster), and a mammal (mouse). In the latter case, median lifespan is doubled if animals live in a non-sterile vivarium. The lifespan increase is accompanied by rectangularization of the survival curves (an increase in survival is much larger at early than at late ages) and disappearance of typical traits of senescence or retardation of their development. Data summarized here and in the preceding papers of this series suggest that mitochondria-targeted antioxidant SkQ1 is competent in slowing down execution of an aging program responsible for development of age-related senescence.