New model systems for studying the evolutionary biology of aging: crustacea.

Progress in any area of biology has generally required work on a variety of organisms. This is true because particular species often have characteristics that make them especially useful for addressing specific questions. Recent progress in studying the evolutionary biology of senescence has been made through the use of new species, such as Caenorhabditis elegans and Drosophila melanogaster, because of the ease of working with them in the laboratory and because investigators have used theories for the evolution of aging as a basis for discovering the underlying mechanisms. I describe ways of finding new model systems for studying the evolutionary mechanisms of aging by combining the predictions of theory with existing information about the natural history of organisms that are well-suited to laboratory studies. Properties that make organisms favorable for laboratory studies include having a short generation time, high fecundity, small body size, and being easily cultured in a laboratory environment. It is also desirable to begin with natural populations that differ in their rate of aging. I present three scenarios and four groups of organisms which fulfill these requirements. The first two scenarios apply to well-documented differences in age/size specific predation among populations of guppies and microcrustacea. The third is differences among populations of fairy shrimp (Anostraca) in habitat permanence. In all cases, there is an environmental factor that is likely to select for changes in the life history, including aging, plus a target organism which is well-suited for laboratory studies of aging.