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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.

SUBMITTER: Zohdy S

PROVIDER: S-EPMC4212904 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Teeth, sex, and testosterone: aging in the world's smallest primate.

Zohdy Sarah S Gerber Brian D BD Tecot Stacey S Blanco Marina B MB Winchester Julia M JM Wright Patricia C PC Jernvall Jukka J

PloS one 20141029 10

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 w ...[more]

PMID: 25354041

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Project description:BackgroundPaedocypris, a highly developmentally truncated fish from peat swamp forests in Southeast Asia, comprises the world's smallest vertebrate. Although clearly a cyprinid fish, a hypothesis about its phylogenetic position among the subfamilies of this largest teleost family, with over 2400 species, does not exist. Here we present a phylogenetic analyses of 227 cypriniform taxa, including 213 cyprinids, based upon complete mitochondrial DNA cytochrome b nucleotide sequences in order to determine the phylogenetic position of Paedocypris and to study the evolution of miniaturization among cyprinids.ResultsOur analyses reveal a strongly supported sister group relationship (clade C) between Paedocypris and Sundadanio, another developmentally truncated miniature cyprinid. Clade C was resolved as sister group of a larger clade characterized by small rasborine taxa (clade D). We found that miniaturised taxa are more numerous in the rasborine clade A, formed by clades C and D, than in any other cyprinid clade. The consensus cytb in cyprinids includes 380 amino acids and an incomplete T-- stop codon. We noted that a few cyprinids mostly rasborine taxa placed within clade A had either a TAA or TAG stop codon, 376, 378, or 381 amino acids, and up to 10 base pairs (bp) of noncoding region before the 5' end of the tRNA-Thr. Our relaxed molecular clock estimates revealed high divergence times for the Sundadanio and Paedocypris clades and provide a first temporal framework for the evolution of miniaturization among cyprinids.ConclusionPaedocypris belongs to a clade (Rasborinae clade A) that shows recurrent miniaturization, including both taxa characterized by developmental truncation and by proportioned dwarfism. Its closest relative is another miniaturized taxon, the genus Sundadanio. We conclude that the miniaturized cyprinids with remarkable morphological novelties, like Paedocypris and Danionella, are at the same time the most developmentally truncated taxa. The miniaturized cyprinids with no or few developmental truncations like Boraras, Microrasbora, and Horadandia show no such evolutionary novelties.

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Teeth, sex, and testosterone: aging in the world's smallest primate.

Publications

Teeth, sex, and testosterone: aging in the world's smallest primate.

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