Ambiguities in using telomere length for age determination in two North American bat species

Abstract

The age of an animal, determined by time (chronological age) as well as genetic and environmental factors (biological age), influences the likelihood of mortality and reproduction and thus the animal’s contribution to population growth. For many long-lived species, such as bats, a lack of external and morphological indicators has made determining age a challenge, leading researchers to examine genetic markers of age for application to demographic studies. One widely studied biomarker of age is telomere length, which has been related both to chronological and biological age across taxa, but only recently has begun to be studied in bats. We assessed telomere length from the DNA of known-age and minimum known-age individuals of two bat species using a quantitative PCR assay. We determined that telomere length was quadratically related to chronological age in big brown bats (Eptesicus fuscus), although it had little predictive power for accurate age determination of unknown-age individuals. The relationship was different in little brown bats (Myotis lucifugus), where telomere length instead was correlated with biological age, apparently due to infection and wing damage associated with white-nose syndrome. Furthermore, we showed that wing biopsies currently are a better tissue source for studying telomere length in bats than guano and buccal swabs; the results from the latter group were more variable and potentially influenced by storage time. Refinement of collection and assessment methods for different non-lethally collected tissues will be important for longitudinal sampling to better understand telomere dynamics in these long-lived species. Although further work is needed to develop a biomarker capable of determining chronological age in bats, our results suggest that biological age, as reflected in telomere length, may be influenced by extrinsic stressors such as disease.

Taking flight: An ecological, evolutionary and genomic perspective on bat telomeres

“…Similar results were observed in M. lucifugus (Ineson et al, 2020), where cross-sectional and longitudinal analyses showed no relationship between age and rTL, supporting the hypothesis that factors other than age contribute to telomere dynamics in long-lived Myotis species (Foley et al, 2018). In the same study, while age only explained a small amount of variation in rTL, telomeres in E. fuscus increased in length up to eight years of age then decreased in length following a quadratic pattern (Ineson et al, 2020). While telomere attrition did not correlate with age, M. lucifugus affected by the fungal disease white-nose syndrome (WNS) showed significantly shorter telomeres than those with no infection (Ineson et al, 2020).…”

“…In the same study, while age only explained a small amount of variation in rTL, telomeres in E. fuscus increased in length up to eight years of age then decreased in length following a quadratic pattern (Ineson et al, 2020). While telomere attrition did not correlate with age, M. lucifugus affected by the fungal disease white-nose syndrome (WNS) showed significantly shorter telomeres than those with no infection (Ineson et al, 2020). This provides additional support for the hypothesis that external factors influence patterns observed in some of the longest lived bats.…”

“…Similar results were observed in M . lucifugus (Ineson et al, 2020), where cross‐sectional and longitudinal analyses showed no relationship between age and rTL, supporting the hypothesis that factors other than age contribute to telomere dynamics in long‐lived Myoti s species (Foley et al, 2018). In the same study, while age only explained a small amount of variation in rTL, telomeres in E .…”

“…with the bats showing low expression of telomerase (Gomes et al, 2011) and no shortening of telomeres with age (Ineson et al, 2020).…”

“…was not examined in this study (Ineson et al, 2020) wing is a robust, minimally invasive tissue for rTL measures in bats (Power et al, 2021).…”