Sperm telomere length correlates with blood telomeres and body size in red-sided garter snakes, Thamnophis sirtalis parietalis

摘要

Telomeres, tandem repeats of TTAGGG at the ends of chromosomes, are highly dynamic structures that shorten in response to a variety of factors, including organismal stress and tissue-specific growth rates. Cell turnover rates are frequently linked to their functions, resource availability and telomere dynamics. Using male red-sided garter snakes, Thamnophis sirtalis parietalis, as a model, we investigated the relationship between telomere length in sperm cells, blood cells telomere length and a growth proxy (age-adjusted body length and mass). This relationship is interesting because snakes exhibit indeterminate growth and because these garter snakes have a dissociated reproductive cycle where spermatogenesis occurs months prior to the mating season. In this study, we determined sperm telomere length (STL) and male age using qPCR and skeletochronology, respectively. Sperm telomere length correlated positively with snout-vent length (SVL) and with age-adjusted SVL as a proxy for growth rate (residuals of size against age regression, hereafter growth), but not with age. Although an individual's STL is correlated with blood telomere length (BTL), sperm telomeres are 60% longer than blood telomeres. In previous work, we have shown that BTL is shorter in older males and unrelated to SVL or any growth rate proxies. We hypothesized that STL is related to growth and SVL because growth and sperm production both occur during summer when resources are most abundant and stress lowest. This study is the first to compare telomere dynamics between cell types in a snake and supports growing evidence that telomere dynamics may be highly tissue-specific and driven by the life-history strategy of an organism.