Extended Longevity of Reproductives Appears to be Common in Fukomys Mole-Rats (Rodentia, Bathyergidae)

Abstract

African mole-rats (Bathyergidae, Rodentia) contain several social, cooperatively breeding species with low extrinsic mortality and unusually high longevity. All social bathyergids live in multigenerational families where reproduction is skewed towards a few breeding individuals. Most of their offspring remain as reproductively inactive “helpers” in their natal families, often for several years. This “reproductive subdivision” of mole-rat societies might be of interest for ageing research, as in at least one social bathyergid (Ansell's mole-rats Fukomys anselli), breeders have been shown to age significantly slower than non-breeders. These animals thus provide excellent conditions for studying the epigenetics of senescence by comparing divergent longevities within the same genotypes without the inescapable short-comings of inter-species comparisons. It has been claimed that many if not all social mole-rat species may have evolved similar ageing patterns, too. However, this remains unclear on account of the scarcity of reliable datasets on the subject. We therefore analyzed a 20-year breeding record of Giant mole-rats Fukomys mechowii, another social bathyergid species. We found that breeders indeed lived significantly longer than helpers (ca. 1.5–2.2fold depending on the sex), irrespective of social rank or other potentially confounding factors. Considering the phylogenetic positions of F. mechowii and F. anselli and unpublished data on a third Fukomys-species (F. damarensis) showing essentially the same pattern, it seems probable that the reversal of the classic trade-off between somatic maintenance and sexual reproduction is characteristic of the whole genus and hence of the vast majority of social mole-rats.

Reproduction, aging and mortality rate in social subterranean mole voles (Ellobius talpinus Pall.)

“…This data is partly in agreement with the observations of Dammann and Burda for African mole-rats, although these authors found only weak gender differences in age-related mortality among breeding and non-breeding animals (Dammann and Burda 2006;Dammann et al 2011). A likely explanation for these speciesspecific differences lies in the fact that the families of African mole-rats usually consist of one dominant reproductive pair and their offspring (Faulkes and Bennett 2001), although multiple and unidentified paternity occurs in nature (Bishop et al 2004;Burland et al 2004).…”

“…In laboratory-housed individuals, longevity does not differ between breeding and non-breeding naked mole-rats (Buffenstein 2005), but this is not the case for social African mole-rats of the Fukomys genera. In at least two species, F. anselli and F. mechowii, breeders live twice as long as non-breeders under both natural (Schmidt et al 2013) and laboratory (Dammann and Burda 2006;Dammann et al 2011) conditions. Therefore, this difference may be associated not only with a high rate of extrinsic mortality of non-breeders, but also with different patterns of intrinsic mortality.…”

“…On the basis of the observations made for the laboratory colony of northern mole voles that has been maintained in the Institute of Systematics and Ecology of Animals SB RAS for several years, we examined whether the reproductive skew in this species correlates with a mortality skew, as was revealed for African mole-rats (Dammann and Burda 2006;Dammann et al 2011). If so, we wanted to know whether the increased mortality of non-breeders correlated with deterioration in physiological traits that may be essential for survival.…”

The long-lived queen: reproduction and longevity in female eusocial Damaraland mole-rats (Fukomys damarensis)

“…years whereas the mean lifespan of non-reproductive females is 4.56 ± 0.19 S.E. years in captivity (Dammann et al 2011); mean survival of reproductive female Ansell's mole-rats is almost twice that of non-breeding females (Dammann & Burda 2006). Naked mole rats (Heterocephalus glaber) exhibit no difference in maximum lifespan between breeding and nonbreeding females in captivity (Sherman & Jarvis 2002); however, according to Braude in a personal communication, breeding females can live at least four times longer than non-breeding individuals in the wild (it is unclear whether the non-breeders referred to in this study include male cohorts; Buffenstein 2008).…”

Trading new neurons for status: Adult hippocampal neurogenesis in eusocial Damaraland mole-rats

“…Since neurogenesis declines with age, species with long life spans typically show low rates of neurogenesis as adults (Amrein et al, 2011). However, life spans are not uniform amongst the different castes of a mole-rat colony, breeding animals may live twice as long as their non-breeding counterparts (Dammann et al, 2011). Also, the heaviest animals in a mole-rat colony are not necessarily the oldest.…”