The Potential of Comparative Biology to Reveal Mechanisms of Aging in Rotifers

Abstract Despite decades of research, the genetic causes of aging remain elusive. The natural phenotypic and genetic diversity in the Brachionus plicatilis species complex of rotifers can address this challenge. Rotifers are small aquatic invertebrates that have been used in aging studies for nearly 100 years but have only recently emerged as a modern model system. Ease of culturing, small size, and short generation time offer experimental advantages. Caloric restriction (CR), reduced temperature, hypoxia, c-Jun N-terminal kinase or target of rapamycin inhibition, and glycerol supplementation increase life span and in some cases health span, suggesting the physiological and genetic basis of these interventions are conserved between rotifers, established models, and humans. The life cycle of Brachionus produces three types of genetically identical females that have different life span, health span, and fecundity responses to CR interventions, allowing investigation of epigenetic and other maternal effects. There is also variation among closely related members of the B. plicatilis species complex in their response to these interventions, ranging from increases to decreases in life span, health span, and fecundity. Some strains display the classic trade-off between life span and fecundity while others show an increase in both, with implications for the role of the disposable soma theory of aging in different environments. Comparing the response of these natural variants can be a powerful tool to identify genetic pathways modulating health span.