Is the Mahali mole-rat (Cryptomys hottentotus mahali) a spontaneous or induced ovulator?

The Mahali mole-rat (Cryptomys hottentotus mahali (Roberts, 1913)) is a social, cooperatively breeding subterranean rodent that breeds aseasonally. Only one female in a colony breeds and the remaining females are reproductively suppressed. When the opportunity arises, these non-reproductive females disperse from the natal colony to escape reproductive suppression and pair up with an unrelated male to start a new colony. This study set out to determine whether female Mahali mole-rats are induced or spontaneous ovulators once separated from the reproductive suppression of the breeding female. Fifteen separated females were subjected to three treatments: housed separately without a male (A), allowed chemical, but not physical, contact with a vasectomised male (NPC), and placed in direct contact with a vasectomised male (PC). Urine was collected from all females under each treatment every 2 days for 40 days. Only females housed in the PC treatment exhibited heightened progesterone concentrations and corpora lutea of ovulation in the ovaries. Furthermore, males possessed epidermal spines on the shaft of the penises that may be used to stimulate the cervix of the female during copulation. These findings suggest that the Mahali mole-rat is an induced ovulator.The SARChI chair of Mammalian Behavioural Ecology and Physiology from the DST–NRF South Africa, the National Research Foundation and the University of Pretoria.http://www.nrcresearchpress.com/journal/cjzhj2020Mammal Research InstituteZoology and Entomolog

How hornbills handle heat : sex-specific thermoregulation in the southern yellow-billed hornbill

At a global scale, thermal physiology is correlated with climatic variables such as temperature and aridity. There is also evidence that thermoregulatory traits vary with fine-scale microclimate, but this has received less attention in endotherms. Here, we test the hypothesis that avian thermoregulation varies with microclimate and behavioural constraints in a non-passerine bird. Male and female southern yellowbilled hornbills (Tockus leucomelas) experience markedly different microclimates while breeding, with the female sealing herself into a tree cavity and moulting all her flight feathers during the breeding attempt, becoming entirely reliant on the male for provisioning. We examined interactions between resting metabolic rate (RMR), evaporative water loss (EWL) and core body temperature (Tb) at air temperatures (Ta) between 30°C and 52°C in male and female hornbills, and quantified evaporative cooling efficiencies and heat tolerance limits. At thermoneutral Ta, neither RMR, EWL nor Tb differed between sexes. At Ta >40°C, however,RMRand EWL of females were significantly lower than those of males, by ∼13% and ∼17%, respectively, despite similar relationships between Tb and Ta, maximum ratio of evaporative heat loss to metabolic heat production and heat tolerance limits (∼50°C). These sex-specific differences in hornbill thermoregulation support the hypothesis that avian thermal physiology can vary within species in response to fine-scalemicroclimatic factors. In addition,Q10 for RMR varied substantially, with Q10 ≤2 in some individuals, supporting recent arguments that active metabolic suppression may be an underappreciated aspect of endotherm thermoregulation in the heat.The National Research Foundation SARChI chair for Mammal Behavioural Ecology and Physiology, the SARChI chair of Conservation Physiology, the Centre of Excellence at the FitzPatrick Institute of African Ornithology and the Claude Leon Foundation.http://jeb.biologists.orgam2022Mammal Research InstituteZoology and Entomolog

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

Climate change has caused aridification which can alter habitat vegetation, soil and precipitation profiles potentially affecting resident species. Vegetation and soil profiles are important for subterranean mole-rats as increasing aridity causes soils to become harder and geophytes less evenly distributed, and the inter-geophyte distance increases. Mole-rats obtain all water and dietary requirements from geophytes, and thus digging in harder soils may amplify stressors (hyperthermia, dehydration- or exercise-induced damage). This study assessed the oxidative status of the wild common mole-rat along an aridity gradient (arid, semi-arid and mesic). Kidney and liver oxidative markers, including total oxidant status (TOS), total antioxidant capacity (TAC), oxidative stress index (OSI), malondialdehyde (MDA) and superoxide dismutase (SOD) were measured. Liver oxidative status did not demonstrate any significance with the degree of the aridity gradient. Aridity affected the TAC and OSI of the kidney, with individuals in the most arid habitats possessing the highest TAC. The evolution of increased group size to promote survival in African mole-rats in arid habitats may have resulted in the additional benefit of reduced oxidative stress in the kidneys. The SOD activity of the kidneys was higher than that of the liver with lower oxidative damage, suggesting this species pre-emptively protects its kidneys as these are important for water balance and retention

Naked mole-rat brown fat thermogenesis is diminished during hypoxia through a rapid decrease in UCP1

Naked mole-rats are among the most hypoxia-tolerant mammals. During hypoxia, their body temperature (Tb) decreases via unknown mechanisms to conserve energy. In small mammals, non-shivering thermogenesis in brown adipose tissue (BAT) is critical to Tb regulation; therefore, we hypothesize that hypoxia decreases naked mole-rat BAT thermogenesis. To test this, we measure changes in Tb during normoxia and hypoxia (7% O2; 1–3 h). We report that interscapular thermogenesis is high in normoxia but ceases during hypoxia, and Tb decreases. Furthermore, in BAT from animals treated in hypoxia, UCP1 and mitochondrial complexes I-V protein expression rapidly decrease, while mitochondria undergo fission, and apoptosis and mitophagy are inhibited. Finally, UCP1 expression decreases in hypoxia in three other social African mole-rat species, but not a solitary species. These findings suggest that the ability to rapidly down-regulate thermogenesis to conserve oxygen in hypoxia may have evolved preferentially in social species.An NSERC Discovery grants, a Canada Research Chair and an University of Ottawa Research Chair. Collection and housing of mole-rats in Africa were funded by a SARChI grant.http://www.nature.com/naturecommunicationsam2022Zoology and Entomolog

The relationship between hypoxia exposure and circulating cortisol levels in social and solitary African mole-rats: An initial report

Hypoxemia from exposure to intermittent and/or acute environmental hypoxia (lower oxygen concentration) is a severe stressor for many animal species. The response to hypoxia of the hypothalamic-pituitary-adrenal axis (HPA-axis), which culminates in the release of glucocorticoids, has been well-studied in hypoxia-intolerant surface-dwelling mammals. Several group-living (social) subterranean species, including most African mole -rats, are hypoxia-tolerant, likely due to regular exposure to intermittent hypoxia in their underground bur-rows. Conversely, solitary mole-rat species, lack many adaptive mechanisms, making them less hypoxia-tolerant than the social genera. To date, the release of glucocorticoids in response to hypoxia has not been measured in hypoxia-tolerant mammalian species. Consequently, this study exposed three social African mole-rat species and two solitary mole-rat species to normoxia, or acute hypoxia and then measured their respective plasma gluco-corticoid (cortisol) concentrations. Social mole-rats had lower plasma cortisol concentrations under normoxia than the solitary genera. Furthermore, individuals of all three of the social mole-rat species exhibited signifi-cantly increased plasma cortisol concentrations after hypoxia, similar to those of hypoxia-intolerant surface -dwelling species. By contrast, individuals of the two solitary species had a reduced plasma cortisol response to acute hypoxia, possibly due to increased plasma cortisol under normoxia. If placed in perspective with other closely related surface-dwelling species, the regular exposure of the social African mole-rats to hypoxia may have reduced the basal levels of the components for the adaptive mechanisms associated with hypoxia exposure, including circulating cortisol levels. Similarly, the influence of body mass on plasma cortisol levels cannot be ignored. This study demonstrates that both hypoxia-tolerant rodents and hypoxia-intolerant terrestrial laboratory-bred rodents may possess similar HPA-axis responses from exposure to hypoxia. Further research is required to confirm the results from this pilot study and to further confirm how the cortisol concentrations may influence responses to hypoxia in African mole-rats

The relationship between hypoxia exposure and circulating cortisol levels in social and solitary African mole-rats : an initial report

Hypoxemia from exposure to intermittent and/or acute environmental hypoxia (lower oxygen concentration) is a severe stressor for many animal species. The response to hypoxia of the hypothalamic–pituitary-adrenal axis (HPA-axis), which culminates in the release of glucocorticoids, has been well-studied in hypoxia-intolerant surface-dwelling mammals. Several group-living (social) subterranean species, including most African mole-rats, are hypoxia-tolerant, likely due to regular exposure to intermittent hypoxia in their underground burrows. Conversely, solitary mole-rat species, lack many adaptive mechanisms, making them less hypoxia-tolerant than the social genera. To date, the release of glucocorticoids in response to hypoxia has not been measured in hypoxia-tolerant mammalian species. Consequently, this study exposed three social African mole-rat species and two solitary mole-rat species to normoxia, or acute hypoxia and then measured their respective plasma glucocorticoid (cortisol) concentrations. Social mole-rats had lower plasma cortisol concentrations under normoxia than the solitary genera. Furthermore, individuals of all three of the social mole-rat species exhibited significantly increased plasma cortisol concentrations after hypoxia, similar to those of hypoxia-intolerant surface-dwelling species. By contrast, individuals of the two solitary species had a reduced plasma cortisol response to acute hypoxia, possibly due to increased plasma cortisol under normoxia. If placed in perspective with other closely related surface-dwelling species, the regular exposure of the social African mole-rats to hypoxia may have reduced the basal levels of the components for the adaptive mechanisms associated with hypoxia exposure, including circulating cortisol levels. Similarly, the influence of body mass on plasma cortisol levels cannot be ignored. This study demonstrates that both hypoxia-tolerant rodents and hypoxia-intolerant terrestrial laboratory-bred rodents may possess similar HPA-axis responses from exposure to hypoxia. Further research is required to confirm the results from this pilot study and to further confirm how the cortisol concentrations may influence responses to hypoxia in African mole-rats.SARCHI Chair of Mammal Behavioural Ecology and Physiology, a National Geographic Society Explorers Grant, Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants and Canada Research Chairs.http://www.elsevier.com/locate/ygcenam2024Zoology and EntomologySDG-03:Good heatlh and well-beingSDG-15:Life on lan

Nutritionally Enhanced Staple Food Crops

Crop biofortification is a sustainable and cost-effective strategy to address malnutrition in developing countries. This review synthesizes the progress toward developing seed micronutrient-dense cereals and legumes cultivars by exploiting natural genetic variation using conventional breeding and/or transgenic technology, and discusses the associated issues to strengthen crop biofortification research and development. Some major QTL for seed iron and zinc, seed phosphorus, and seed phytate in common bean, rice,J;md wheat have been mapped. An iron reductase QTL associated with seed-iron ~QTL is found in common bean where the genes coding for candidate enzymes involved in phytic acid synthesis have also been mapped. Candidate genes for Ipa co segregate with mutant phenotypes identified in rice and soybean. The Gpe-B1 locus in wild emmer wheat accelerates senescence and increases nutrient remobilization from leaves to developing seeds, and another gene named TtNAM-B1 affecting these traits has been cloned. Seed iron-dense common bean and rice in Latin America; seed iron-dense common bean in eastern and southern Africa;....

The joint effect of micro- and macro-climate on the thermoregulation and heat dissipation of two African mole-rat (Bathyergidae) sub-species, Cryptomys hottentotus mahali and C. h. pretoriae

The effect of the macro- and microclimate on small mammal thermoregulation in the past has been studied independently instead of investigating the dual effect of both the components. This study addresses this dearth in knowledge by exploring the dual effect of both micro- and macro-climate on the thermoregulatory responses of two subterranean rodent species belonging to the family Bathyergidae, namely the more arid dwelling Mahali mole-rat (Cryptomys hottentotus mahali) and less arid dwelling Highveld mole-rat (C. h. pretoriae). Open flow through respirometry was used to quantify resting metabolic rates (RMR), evaporative water loss (EWL), core body temperature (Tb), the ratio between the evaporative heat loss and metabolic heat production (EHL/MHP: evaporative cooling capacity) and conductance (Cdry) over a range of increasing ambient temperatures (Ta; 20–42 °C). Furthermore, RMR, EWL, Tb, EHL/MHP and Cdry were measured at the mole-rat's thermal maxima (43 °C). At cooler temperatures, the arid-dwelling C. h. mahali possesses a broader thermoneutral zone (~5 °C; 27.2–32.1 °C), while C. h. pretoriae possess a single thermoneutral point (33.6 °C). This is in response to the greater selection pressure to conserve energy in the more arid regions inhabited by C. h. mahali. Contrastingly, at hotter temperatures, there were no significant thermoregulatory differences in EWL, EHL/MHP or Cdry responses between the two sub-species, as expected due to the limitations bestowed by the buffered microclimates (burrow systems). Thus, neither macro-climate, nor micro-climate singularly moulds the thermoregulatory adaptations, but rather, it appears to be a combined effect from both climates. Other small endotherms may share this dual response, and therefore, it is crucial to incorporate the effect of both macro- and microclimates into future climate models when determining the ecological capabilities and persistence of a species

The joint effect of micro- and macro-climate on the thermoregulation and heat dissipation of two African mole-rat (Bathyergidae) sub-species, Cryptomys hottentotus mahali and C. h. pretoriae

The effect of the macro- and microclimate on small mammal thermoregulation in the past has been studied independently instead of investigating the dual effect of both the components. This study addresses this dearth in knowledge by exploring the dual effect of both micro- and macro-climate on the thermoregulatory responses of two subterranean rodent species belonging to the family Bathyergidae, namely the more arid dwelling Mahali mole-rat (Cryptomys hottentotus mahali) and less arid dwelling Highveld mole-rat (C. h. pretoriae). Open flow through respirometry was used to quantify resting metabolic rates (RMR), evaporative water loss (EWL), core body temperature (Tb), the ratio between the evaporative heat loss and metabolic heat production (EHL/MHP: evaporative cooling capacity) and conductance (Cdry) over a range of increasing ambient temperatures (Ta; 20–42 °C). Furthermore, RMR, EWL, Tb, EHL/MHP and Cdry were measured at the mole-rat's thermal maxima (43 °C). At cooler temperatures, the arid-dwelling C. h. mahali possesses a broader thermoneutral zone (~5 °C; 27.2–32.1 °C), while C. h. pretoriae possess a single thermoneutral point (33.6 °C). This is in response to the greater selection pressure to conserve energy in the more arid regions inhabited by C. h. mahali. Contrastingly, at hotter temperatures, there were no significant thermoregulatory differences in EWL, EHL/MHP or Cdry responses between the two sub-species, as expected due to the limitations bestowed by the buffered microclimates (burrow systems). Thus, neither macro-climate, nor micro-climate singularly moulds the thermoregulatory adaptations, but rather, it appears to be a combined effect from both climates. Other small endotherms may share this dual response, and therefore, it is crucial to incorporate the effect of both macro- and microclimates into future climate models when determining the ecological capabilities and persistence of a species