Plasma oxidative stress in reproduction of two eusocial African mole-rat species, the naked mole-rat and the Damaraland mole-rat

Abstract

One of the most prominent life-history trade-offs involves the cost of reproduction. Oxidative stress has been proposed to be involved in this trade-off and has been associated with reduced life span. There is currently an unclear relationship between oxidative cost and the reproduction-longevity trade-off. The current study, using a non-lethal and minimally invasive (only a single blood sample and no euthanasia) method, investigated whether an oxidative cost (oxidative stress) to reproduction would be apparent in two long-lived eusocial mole-rats, the naked mole-rat (NMR), Heterocephalus glaber, and the Damaraland mole-rat (DMR), Fukomys damarensis, where breeding colony members live longer than non-breeder conspecifics. We measured the direct redox balance in plasma by measuring the oxidative stress index (OSI) based on the ratio of total oxidant status and total antioxidant activity in breeders and non-breeders of both sexes, in the two species. NMR had significantly higher OSI between breeders and non-breeders of each sex, whereas DMR showed no significant differences except for total antioxidant capacity (TAC). The mode of reproductive suppression and the degree of reproductive investment in NMR may explain to some degree the redox balance difference between breeders and non-breeders. DMR show minimal physiological changes between breeders and non-breeders except for the mode of reproduction, which may explain some variations in TAC and TOS values, but similar OSI between breeders and non-breeders.

Tissue Oxidative Ecology along an Aridity Gradient in a Mammalian Subterranean Species

“…Therefore, only male and female non-breeders were used in this study (see Hart, et al [ 98 ] on how reproductive status was determined). The use of non-breeders only circumvents complications of oxidative stress associated with reproduction [ 99 , 100 ].…”

The Evolution and Ecology of Oxidative and Antioxidant Status: A Comparative Approach in African Mole-Rats

“…All animals used in this study were considered adults and reproductively inactive (non-breeders) {see Bennett and Faulkes [125] on how reproductive status was determined} (Table 1). The use of non-breeders avoids complications between breeder and non-breeder comparisons associated with oxidative stress due to reproduction [74,79] and the effects of reproductive suppression differences [74,79,[98][99][100][101][102][103][104][105][106]125,126] (Supplementary File S1).…”

“…Despite the interest in NMRs as a conundrum in the oxidative stress theory of ageing [ 36 , 45 , 57 , 62 , 64 , 65 , 66 , 67 ], a comparison of their redox status with that of other Bathyergidae has not previously been carried out. This is surprising, as oxidative markers in tissues [ 45 ] and plasma [ 74 ] were previously found to differ, and Dammann [ 51 ] proposed that the importance of oxidative stress in bathyergids may be underestimated if only NMRs and mice are compared, or that the impact of oxidative stress may very well differ between the NMR and other African mole-rat species. Comparisons between the NMR and other African mole-rat species may allow for identifying the ecological and physiological factors involved in redox biology that are not apparent when considering only one species.…”

The Cost of Reproduction in a Cooperatively Breeding Mammal: Consequences of Seasonal Variation in Rainfall, Reproduction, and Reproductive Suppression

“…In the current study, we set out to investigate seasonal differences in the oxidative cost to reproduction in a wild population of seasonally breeding social highveld mole-rats (C. hottentotus pretoriae), using a non-lethal and minimally invasive (only a single blood sample and no euthanasia) method (Jacobs et al, 2021a). We predicted that seasonal differences in oxidative markers (total antioxidant capacity-TAC; total oxidant status-TOS; OSI-Oxidative stress index; MDA-malondialdehyde) would be similar between BMs and NBMs throughout the year as both BMs and NBMs show the ability to actively breed throughout the year by possessing sperm in the testes and vas deferens.…”