20 - Strongyloides ratti: A Nematode with Extraordinary Plasticity in Aging

Abstract

This chapter discusses the aging process of Strongyloides ratti, a nematode with an unusual life cycle. Many animal species show phenotypic plasticity in aging, of which there are two major types. The first is the relatively limited response to a changing environment by a given stage in the life cycle. Strongyloides is a genus of parasitic nematodes that infect a wide variety of vertebrates. The parasitic stages of S. ratti are maintained in the laboratory by infecting rats. Immunologically normal animals mount an immune response against these infections, such that the infections are lost after four to six weeks. In S. ratti parasitic females, maximum life span is 403 days, which compares to 5 days in the free-living morph. In C. elegans, there is an increase in intestinal autofluorescence with age, similar to accumulation of age-pigment (lipofuscin) seen during mammalian aging. There is a similar increase in autofluorescence with age in free-living S. ratti morphs. The parasitic and free-living female morphs of S. ratti are genetically identical. Therefore, differences between these morphs must be because of differences in gene expression.