Longevity Of Bats Research Articles

Morphological, Anatomical, and Physiological Signs of Senescence in the Great Fruit-Eating Bat (Artibeus lituratus)

The longevity of bats is longer than expected based on their small body sizes and high metabolic rate. However, signs of senescence have been poorly studied for free-living bats, especially for Neotropical species, because elderly individuals are challenging to find in the wild, and long-term mark-recapture studies are lacking. Here, we present the first record of a free-living Neotropical frugivorous bat, a female Artibeus lituratus (family Phyllostomidae), with impressive signs of senescence. We compare the elderly bat with conspecific juveniles and non-elderly adults morphologically, anatomically, and physiologically. The most noticeable signs of senescence were a significant loss of fur, dark spots on the skin, excessive dental wear, and reduced ability to assimilate sugar. These traits indicate that bats' challenges as they get old can be associated with reduced thermal insulation, ability to chew, and nutrient assimilation. However, by reducing extrinsic causes of mortality, flying capability in old bats with clear signs of senescence may represent a vital survival trait associated with the long lifespan of these animals.

EPAS1 prevents telomeric damage-induced senescence by enhancing transcription of TRF1, TRF2, and RAD50.

Telomeres are nucleoprotein structures located at the end of each chromosome, which function in terminal protection and genomic stability. Telomeric damage is closely related to replicative senescence in vitro and physical aging in vivo. As relatively long-lived mammals based on body size, bats display unique telomeric patterns, including the up-regulation of genes involved in alternative lengthening of telomeres (ALT), DNA repair, and DNA replication. At present, however, the relevant molecular mechanisms remain unclear. In this study, we performed cross-species comparison and identified EPAS1, a well-defined oxygen response gene, as a key telomeric protector in bat fibroblasts. Bat fibroblasts showed high expression of EPAS1, which enhanced the transcription of shelterin components TRF1 and TRF2, as well as DNA repair factor RAD50, conferring bat fibroblasts with resistance to senescence during long-term consecutive expansion. Based on a human single-cell transcriptome atlas, we found that EPAS1 was predominantly expressed in the human pulmonary endothelial cell subpopulation. Using in vitro-cultured human pulmonary endothelial cells, we confirmed the functional and mechanistic conservation of EPAS1 in telomeric protection between bats and humans. In addition, the EPAS1 agonist M1001 was shown to be a protective compound against bleomycin-induced pulmonary telomeric damage and senescence. In conclusion, we identified a potential mechanism for regulating telomere stability in human pulmonary diseases associated with aging, drawing insights from the longevity of bats.

DNA methylation predicts age and provides insight into exceptional longevity of bats

Exceptionally long-lived species, including many bats, rarely show overt signs of aging, making it difficult to determine why species differ in lifespan. Here, we use DNA methylation (DNAm) profiles from 712 known-age bats, representing 26 species, to identify epigenetic changes associated with age and longevity. We demonstrate that DNAm accurately predicts chronological age. Across species, longevity is negatively associated with the rate of DNAm change at age-associated sites. Furthermore, analysis of several bat genomes reveals that hypermethylated age- and longevity-associated sites are disproportionately located in promoter regions of key transcription factors (TF) and enriched for histone and chromatin features associated with transcriptional regulation. Predicted TF binding site motifs and enrichment analyses indicate that age-related methylation change is influenced by developmental processes, while longevity-related DNAm change is associated with innate immunity or tumorigenesis genes, suggesting that bat longevity results from augmented immune response and cancer suppression.

Why do bats live so long?-Possible molecular mechanisms.

Contrasting with several theories of ageing, bats are mammals with remarkable longevity despite their high metabolic rate, living on average three times more than other mammals of equal size. The question of how bats live a long time has attracted considerable attention, and they have thus been related to immortal fantasy characters like Dracula in the novel by Bram Stoker. Several ecological and physiological features, such as reduction in mortality risks, delayed sexual maturation and hibernation, have been linked to bats' long lifespan. However, there is still very little information about the molecular mechanisms associated with the longevity of bats. In this regard, the present work tries to summarize current knowledge about how bats can live for so long, taking into consideration nutritional factors, oxidative metabolism, protein homeostasis, stress resistance, DNA repair, mitochondrial physiology and cancer resistance.

Rare catastrophic events drive population dynamics in a bat species with negligible senescence

Bats are remarkably long-lived with lifespans exceeding even those of same-sized birds. Despite a recent interest in the extraordinary longevity of bats very little is known about the shape of mortality over age, and how mortality rates are affected by the environment. Using a large set of individual-based data collected over 19 years in four free-ranging colonies of Bechstein’s bats (Myotis bechsteinii), we found no increase in the rate of mortality and no decrease in fertility demonstrating no senescence until high ages. Our finding of negligible senescence is highly unusual for long-lived mammals, grouping Bechstein’s bats with long-lived seabirds. The most important determinant of adult mortality was one particular winter season, which affected all ages and sizes equally. Apart from this winter, mortality risk did not differ between the winter and the summer season. Colony membership, a proxy for local environmental conditions, also had no effect. In addition to their implications for understanding the extra-ordinary longevity in bats, our results have strong implications for the conservation of bats, since rare catastrophic mortality events can only be detected in individual based long-term field studies. With many bat species globally threatened, such data are crucial for the successful implementation of conservation programs.

Generation and characterization of bat-induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) were first generated from mouse embryonic fibroblasts in the year 2006. These cells resemble the typical morphology of embryonic stem cells, express pluripotency markers, and are able to transmit through germlines. To date, iPSCs of many species have been generated, whereas generation of bat iPSCs (biPSCs) has not been reported. To facilitate in-depth study of bats at the molecular and cellular levels, we describe the successful derivation of biPSCs with a piggyBac (PB) vector that contains eight reprogramming factors Oct4, Sox2, Klf4, Nanog, cMyc, Lin28, Nr5a2, and miR302/367. These biPSCs were cultured in media containing leukemia inhibitory factor and three small molecule inhibitors (CHIR99021, PD0325901, and A8301). They retained normal karyotype, displayed alkaline phosphatase activity, and expressed pluripotency markers Oct4, Sox2, Nanog, TBX3, and TRA-1-60. They could differentiate in vitro to form embryoid bodies and in vivo to form teratomas that contained tissue cells of all three germ layers. Generation of biPSCs will facilitate future studies on the mechanisms of antiviral immunity and longevity of bats at the cellular level.

Sex‐Biased Senescence in a Polygynous Bat Species

AbstractBats live substantially longer than any other similar‐sized mammal despite high metabolic rates during flight. The underlying causes for the longevity of bats and the question whether bats exhibit signs of senescence – a progressive deterioration in performance – are still unclear. Here, we describe rates of senescence in individual annual fitness, survival and reproduction using survival and recruitment data collected over an 18‐yr period from 77 males and 81 females in a wild population of Saccopteryx bilineata (greater sac‐winged bat), a polygynous species inhabiting colonies where female groups are defended each by a territorial male. In individuals older than 4 yr of age, individual fitness contribution, survival and recruitment declined with increasing age in males but not in females. Rates of senescence in annual individual fitness and in reproduction of males were at least an order of magnitude higher than those of females. This finding might be explained by the ‘disposable soma theory’ that attributes senescence to an optimal allocation of resources to somatic maintenance and competing traits such as reproduction. The rate of senescence in the survival of males was also significant but of the same order of magnitude as the (non‐significant) rate of females. Unlike many other polygynous mammals, greater sac‐winged bats show little overt male–male competition. As senescence in survival was only weak in males, our results are consistent with the theories for polygynous mammals, which view the trade‐off between male investment in physical traits for intense male–male competition against survival as a major source of the decline of male survival with age. This is the first study to demonstrate sex‐specific senescence rates in a wild population of a small, long‐lived mammalian species.

A New Field Record for Bat Longevity

A new longevity record has been established for a free-living bat-41 years for a male Brandt's bat, Myotis brandtii. The exceptional longevity of bats generally, and this species in particular, should make bats of special interest for researchers studying mechanisms of slow aging.

Ageing studies on bats: a review.

Bat biologists have long known about the exceptional longevity of bats (Order: Chiroptera), which is unusual for mammals of such a small size and a high metabolic rate. Yet relatively few mechanistic studies have focused on this longevity. On average, species of Chiroptera live three times longer than predicted by their body size. In addition, bats have other life history traits that are characteristic of large, long-lived mammals such as few and large offspring and slow growth rates. Bats fit the evolutionary theory of ageing, as their extended longevity is predicted by their ability to escape extrinsic mortality through flight and, in some species, hibernation. They also show tradeoffs between longevity and reproduction, as predicted by the disposable soma theory of ageing. From a physiological perspective, bat longevity reportedly correlates with replicative longevity, low brain calpain activity, and reduced reactive oxygen species production. As long-lived and physiologically interesting organisms, bats may prove to be an informative model system for ageing research.

Testing the free radical theory of aging in bats.

The extended longevity of bats, despite their high metabolic rates, may provide insight to patterns and mechanisms of aging. I tested the free radical theory of aging as an explanation for the extreme longevity of the little brown bat, Myotis lucifugus (maximum life span potential [MLSP] = 34 years). In a comparative study, I measured whole-organism oxygen consumption and mitochondrial hydrogen peroxide production in brain, heart, and kidney tissues from M. lucifugus and short-tailed shrews, Blarina brevicauda (MLSP = 2 years). As predicted by the free radical theory of aging, M. lucifugus produced approximately half the amount of hydrogen peroxide as B. brevicauda. In addition, I compared oxygen consumption and hydrogen peroxide production of adult (approximately 1 year) and juvenile (fully developed and fledged young of the year) M. lucifugus to assess oxidative damage to mitochondria (measured as an increase in hydrogen peroxide production) due to the high metabolic rate associated with flight. Contrary to my prediction, juveniles had significantly higher levels of hydrogen peroxide production than adults. I propose that the decreased free radical production in adults is the result of within-individual selection of efficient mitochondria due to selective pressure created by the high energetic demands of flight.

Reduced free-radical production and extreme longevity in the little brown bat ( Myotis lucifugus) versus two non-flying mammals

The extended longevity of bats, despite their high metabolic rate, may provide insight to patterns and mechanisms of aging. Here I test predictions of the free radical or oxidative stress theory of aging as an explanation for differences in lifespan between the little brown bat, Myotis lucifugus (maximum lifespan potential MLSP=34 years), the short-tailed shrew, Blarina brevicauda (MLSP=2 years), and the white-footed mouse, Peromyscus leucopus (MLSP=8 years) by comparing whole-organism oxygen consumption, hydrogen peroxide production, and superoxide dismutase activity in heart, kidney, and brain tissue. Mitochondria from M. lucifugus produced half to one-third the amount of hydrogen peroxide per unit of oxygen consumed compared to mitochondria from B. brevicauda and P. leucopus, respectively. Superoxide dismutase (SOD) activity did not differ among the three species. These results are similar to those found for birds, which like bats have high metabolic rates and extended longevities, and provide support for the free radical theory of aging as an at least partial explanation for the extreme longevity of bats.

Longevity Records and Notes on Tooth Wear of Bats

The longevity of bats has recently been discussed by Cockrum (1956), including records of 14 years for Myotis lucifugus and five years for Myotis keenii . Our studies of hibernating bats in New England during the winter of 1955–56 have established significant new longevity records for these two species. One female Myotis lucifugus banded in April, 1936, in a cave in Plymouth Union, Vermont, was recovered in November, 1955, in the same cave. This bat would have a minimum age of 20.5 years, since the young of these bats are born in the summer months. Several hundred Myotis lucifugus were banded during the winter of 1936–37 in a mine tunnel in Chester, Massachusetts (Griffin, 1940 a , 1940 b , 1945). The colony in this mine tunnel was studied in detail during the winter of 1955–56 (Hall, 1956). Two male bats, which were banded in May, 1937, were recovered in November, 1955, and two more males were recovered in April, 1956. These four bats could not have been younger than 19.5 years. The one bat from Vermont and four from Massachusetts were all in good condition when recaptured and showed no visible indications of their advanced age. Two of the old bats from Chester, Massachusetts, were sacrificed for a detailed study, …

Homing, Movements, and Longevity of Bats

As far as is known, bats were first banded in the United States in 1916, when Dr. A. A. Allen, an ornithologist, marked five pipistrelles with bird bands (Allen, 1921). Little banding of bats was done during the next 16 years; in fact it was not until 1932 that intensive studies were undertaken. Between 1932 and 1951 a total of 67,279 bats were banded in the United States and Canada. Over 50,000 of these were banded in caves, usually in the wintertime while the bats were in the inactive hibernating condition (Mohr, 1953). Most of these studies were made in the eastern United States. Most of the findings of these banding studies have related to the homing ability, movements, and longevity of various species of the more colonial, cave dwelling bats. No intensive studies have been made of the more solitary tree dwelling bats. The purpose of this paper is to summarize some of these findings of other workers and to add the results of banding studies that I have carried on. Grateful acknowledgement is made to the National Science Foundation for Research Grant G-333 (Investigations of the Mammals of Arizona) for financial assistance for field work in Arizona. I am also grateful to the United States Fish and Wildlife Service for furnishing the bands used in my studies in Illinois, Kansas and Arizona, and to Dr. Fred R. Cagle, Department of Zoology, Tulane University of Louisiana, New Orleans, Louisiana, for making available to me the original banding data for the bats banded in Illinois. Since banding studies usually involve much work, I have often imposed upon my friends, associates and students for assistance. Among those whose efforts warrant special thanks are the following: my wife, Irma Cockrum; Drs. A. B. Leonard and A. B. Wiliams; Lee Beatty and Keith …