title: Teeth, sex, and testosterone: aging in the world's smallest primate.
abstract: Mouse lemurs (Microcebus spp.) are an exciting new primate model for understanding human aging and disease. In captivity, Microcebus murinus develops human-like ailments of old age after five years (e.g., neurodegeneration analogous to Alzheimer's disease) but can live beyond 12 years. It is believed that wild Microcebus follow a similar pattern of senescence observed in captive animals, but that predation limits their lifespan to four years, thus preventing observance of these diseases in the wild. Testing whether this assumption is true is informative about both Microcebus natural history and environmental influences on senescence, leading to interpretation of findings for models of human aging. Additionally, the study of Microcebus longevity provides an opportunity to better understand mechanisms of sex-biased longevity. Longevity is often shorter in males of species with high male-male competition, such as Microcebus, but mouse lemurs are sexually monomorphic, suggesting similar lifespans. We collected individual-based observations of wild brown mouse lemurs (Microcebus rufus) from 2003-2010 to investigate sex-differences in survival and longevity. Fecal testosterone was measured as a potential mechanism of sex-based differences in survival. We used a combination of high-resolution tooth wear techniques, mark-recapture, and hormone enzyme immunoassays. We found no dental or physical signs of senescence in M. rufus as old as eight years (N = 189, ages 1-8, mean = 2.59 ± 1.63 SE), three years older than captive, senescent congeners (M. murinus). Unlike other polygynandrous vertebrates, we found no sex difference in age-dependent survival, nor sex or age differences in testosterone levels. While elevated male testosterone levels have been implicated in shorter lifespans in several species, this is one of the first studies to show equivalent testosterone levels accompanying equivalent lifespans. Future research on captive aged individuals can determine if senescence is partially a condition of their captive environment, and studies controlling for various environmental factors will further our understanding of senescence.
authors.affiliation: Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Centre ValBio Research Station, Ranomafana, Ifanadiana, Madagascar; Department of Environmental Studies, Emory University School of Public Health, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Sarah
authors.initials: S
authors.lastname: Zohdy
authors.affiliation: Colorado Cooperative Fish and Wildlife Research Unit, Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Gerber
authors.affiliation: Centre ValBio Research Station, Ranomafana, Ifanadiana, Madagascar; School of Anthropology, University of Arizona, Tuscon, Arizona, United States of America.
authors.forename: Stacey
authors.initials: S
authors.lastname: Tecot
authors.affiliation: Centre ValBio Research Station, Ranomafana, Ifanadiana, Madagascar; Duke Lemur Center, Durham, North Carolina, United States of America.
authors.forename: Marina B
authors.initials: MB
authors.lastname: Blanco
authors.affiliation: Department of Anthropology, Stony Brook University, Stony Brook, New York, United States of America.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Winchester
authors.affiliation: Centre ValBio Research Station, Ranomafana, Ifanadiana, Madagascar; Department of Anthropology, Stony Brook University, Stony Brook, New York, United States of America.
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Wright
authors.affiliation: Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
authors.forename: Jukka
authors.initials: J
authors.lastname: Jernvall
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D016565:Cheirogaleidae / Q000502:physiology*; D005243:Feces / Q000737:chemistry*; D005260:Female; D008017:Life Expectancy; D008297:Male; D012737:Sex Factors; D016019:Survival Analysis; D013739:Testosterone / Q000378:metabolism*; D057085:Tooth Wear / Q000378:metabolism
chemical_list: D013739:Testosterone