Nigel Bennett - Academia.edu (original) (raw)
Papers by Nigel Bennett
Frontiers in Ecology and Evolution
Biological rhythms are rhythmic fluctuations of biological functions that occur in almost all org... more Biological rhythms are rhythmic fluctuations of biological functions that occur in almost all organisms and on several time scales. These rhythms are generated endogenously and entail the coordination of physiological and behavioural processes to predictable, external environmental rhythms. The light-dark cycle is usually the most prominent environmental cue to which animals synchronise their rhythms. Biological rhythms are believed to provide an adaptive advantage to organisms. In the present review, we will examine the occurrence of circadian and seasonal rhythms in African mole-rats (family Bathyergidae). African mole-rats are strictly subterranean, they very rarely emerge aboveground and therefore, do not have regular access to environmental light. A key adaptation to their specialised habitat is a reduction in the visual system. Mole-rats exhibit both daily and seasonal rhythmicity in a range of behaviours and physiological variables, albeit to different degrees and with large ...
Journal of Thermal Biology, 2021
Modelling of anthropogenic induced climate suggests more frequent and severe heatwaves in the fut... more Modelling of anthropogenic induced climate suggests more frequent and severe heatwaves in the future, which are likely to result in the mass die-off of several species of organisms. Oxidative stress induced by severe heat stress has previously been associated with a reduction in animal cognitive performance, depressed reproduction and lower life expectancy. Little is known about the non-lethal consequences of species should they survive extreme heat exposure. We investigated the oxidative stress experienced by the Namaqua rock mouse, a nocturnal rodent, using two experimental heat stress protocols, a 6 hour acute heat stress protocol without access to water and a 3-day heatwave simulation with ad libitum water. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers of oxidative damage, and superoxide dismutase (SOD) and total antioxidant capacity (TAC) as markers of antioxidant defence. Incubator heat stress (heat and dehydration stress) was brought about by increasing the body temperatures of animals to 39-40.8 °C for 6 hours. Following incubator heat stress, significantly higher levels of MDA were observed in the liver. Dehydration did not explain the variation in oxidative markers and is likely a combined effect of thermal and dehydration stress. Individual body mass was significantly negatively correlated to kidney SOD and lipid peroxidation. A heatwave was simulated using a temperature cycle that would naturally occur during a heatwave in the species' local habitat, with a maximal ambient temperature of 38 °C. Following the simulated heatwave, SOD activity of the kidney demonstrated significantly lowered activity suggesting oxidative stress. Current heat waves in this species have the potential of causing oxidative stress. Heat and dehydration stress following exacerbated temperatures are likely to incur significant oxidative stress in multiple tissues demonstrating the importance of water availability to allow for rehydration to prevent oxidative stress.
Journal of Thermal Biology, 2021
The subterranean niche is a specialised and particularly challenging environment to obtain direct... more The subterranean niche is a specialised and particularly challenging environment to obtain direct physiological and behavioural measurements from free-living animals. Rhythmicity has been examined in many mole-rat species in the laboratory, but field reports are relatively scarce. We implanted Natal mole-rats with temperature loggers in summer and winter to record core body temperature (Tb), before releasing the animals again. Animals were recaptured after two months to recover the loggers. Natal mole-rats can maintain rhythmicity of their Tb in their natural habitat and display seasonal differences in their Tb rhythms. During winter mole-rats have unimodal Tb rhythms, whereas in summer many animals have bimodal Tb patterns, which may be related to temperatures in the foraging burrows close to the soil surface. Individuals from the same colonies frequently exhibited similar rhythms, especially in the larger colonies, which may indicate social entrainment of rhythms. Males and females differ in their seasonal variation of Tb, with males having more variation in winter, while the opposite was true for females. Entire colonies may undergo sporadic torpor bouts, presumably to conserve energy, but the trigger for these events is unknown. This is the first report of torpor occurring in an African mole-rat species. The ability to respond to environmental and social cues, while rhythms remain flexible, can provide an adaptive advantage to animals living in challenging and energetically demanding habitats.
PLOS ONE, 2020
Heat waves are known for their disastrous mass die-off effects due to dehydration and cell damage... more Heat waves are known for their disastrous mass die-off effects due to dehydration and cell damage, but little is known about the non-lethal consequences of surviving severe heat exposure. Severe heat exposure can cause oxidative stress which can have negative consequences on animal cognition, reproduction and life expectancy. We investigated the current oxidative stress experienced by a mesic mouse species, the four striped field mouse,Rhabdomys dilectusthrough a heat wave simulation withad libwater and a more severe temperature exposure with minimal water. Wild four striped field mice were caught between 2017 and 2019. We predicted that wild four striped field mice in the heat wave simulation would show less susceptibility to oxidative stress as compared to a more severe heat stress which is likely to occur in the future. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers for oxidative damage, and superoxi...
Rodents use their forepaws to actively interact with their tactile environment. Studies on the ph... more Rodents use their forepaws to actively interact with their tactile environment. Studies on the physiology and anatomy of glabrous skin that makes up the majority of the forepaw are almost non-existent in the mouse. Here we developed a preparation to record from single sensory fibers of the forepaw and compared anatomical and physiological receptor properties to those of the hind paw glabrous and hairy skin. We found that the mouse forepaw skin is equipped with a very high density of mechanoreceptors; >3 fold more than hind paw glabrous skin. In addition, rapidly adapting mechanoreceptors that innervate Meissner’s corpuscles of the forepaw were several-fold more sensitive to slowly moving mechanical stimuli compared to their counterparts in the hind paw glabrous skin. All other mechanoreceptors types as well as myelinated nociceptors had physiological properties that were invariant regardless of which skin area they occupied. We discovered a novel D-hair receptor innervating a sma...
Mammalian Species, Aug 1, 2006
Journal of Morphology, Mar 10, 2016
Parasites & Vectors, Aug 15, 2014
Journal of Zoology, Jul 1, 2008
Frontiers in Ecology and Evolution, Jun 2, 2022
Mammalian Biology, Sep 1, 2013
Journal of Zoology, Feb 13, 2008
Frontiers in Zoology, 2014
General and Comparative Endocrinology, Jun 1, 2013
Frontiers in Ecology and Evolution
Biological rhythms are rhythmic fluctuations of biological functions that occur in almost all org... more Biological rhythms are rhythmic fluctuations of biological functions that occur in almost all organisms and on several time scales. These rhythms are generated endogenously and entail the coordination of physiological and behavioural processes to predictable, external environmental rhythms. The light-dark cycle is usually the most prominent environmental cue to which animals synchronise their rhythms. Biological rhythms are believed to provide an adaptive advantage to organisms. In the present review, we will examine the occurrence of circadian and seasonal rhythms in African mole-rats (family Bathyergidae). African mole-rats are strictly subterranean, they very rarely emerge aboveground and therefore, do not have regular access to environmental light. A key adaptation to their specialised habitat is a reduction in the visual system. Mole-rats exhibit both daily and seasonal rhythmicity in a range of behaviours and physiological variables, albeit to different degrees and with large ...
Journal of Thermal Biology, 2021
Modelling of anthropogenic induced climate suggests more frequent and severe heatwaves in the fut... more Modelling of anthropogenic induced climate suggests more frequent and severe heatwaves in the future, which are likely to result in the mass die-off of several species of organisms. Oxidative stress induced by severe heat stress has previously been associated with a reduction in animal cognitive performance, depressed reproduction and lower life expectancy. Little is known about the non-lethal consequences of species should they survive extreme heat exposure. We investigated the oxidative stress experienced by the Namaqua rock mouse, a nocturnal rodent, using two experimental heat stress protocols, a 6 hour acute heat stress protocol without access to water and a 3-day heatwave simulation with ad libitum water. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers of oxidative damage, and superoxide dismutase (SOD) and total antioxidant capacity (TAC) as markers of antioxidant defence. Incubator heat stress (heat and dehydration stress) was brought about by increasing the body temperatures of animals to 39-40.8 °C for 6 hours. Following incubator heat stress, significantly higher levels of MDA were observed in the liver. Dehydration did not explain the variation in oxidative markers and is likely a combined effect of thermal and dehydration stress. Individual body mass was significantly negatively correlated to kidney SOD and lipid peroxidation. A heatwave was simulated using a temperature cycle that would naturally occur during a heatwave in the species' local habitat, with a maximal ambient temperature of 38 °C. Following the simulated heatwave, SOD activity of the kidney demonstrated significantly lowered activity suggesting oxidative stress. Current heat waves in this species have the potential of causing oxidative stress. Heat and dehydration stress following exacerbated temperatures are likely to incur significant oxidative stress in multiple tissues demonstrating the importance of water availability to allow for rehydration to prevent oxidative stress.
Journal of Thermal Biology, 2021
The subterranean niche is a specialised and particularly challenging environment to obtain direct... more The subterranean niche is a specialised and particularly challenging environment to obtain direct physiological and behavioural measurements from free-living animals. Rhythmicity has been examined in many mole-rat species in the laboratory, but field reports are relatively scarce. We implanted Natal mole-rats with temperature loggers in summer and winter to record core body temperature (Tb), before releasing the animals again. Animals were recaptured after two months to recover the loggers. Natal mole-rats can maintain rhythmicity of their Tb in their natural habitat and display seasonal differences in their Tb rhythms. During winter mole-rats have unimodal Tb rhythms, whereas in summer many animals have bimodal Tb patterns, which may be related to temperatures in the foraging burrows close to the soil surface. Individuals from the same colonies frequently exhibited similar rhythms, especially in the larger colonies, which may indicate social entrainment of rhythms. Males and females differ in their seasonal variation of Tb, with males having more variation in winter, while the opposite was true for females. Entire colonies may undergo sporadic torpor bouts, presumably to conserve energy, but the trigger for these events is unknown. This is the first report of torpor occurring in an African mole-rat species. The ability to respond to environmental and social cues, while rhythms remain flexible, can provide an adaptive advantage to animals living in challenging and energetically demanding habitats.
PLOS ONE, 2020
Heat waves are known for their disastrous mass die-off effects due to dehydration and cell damage... more Heat waves are known for their disastrous mass die-off effects due to dehydration and cell damage, but little is known about the non-lethal consequences of surviving severe heat exposure. Severe heat exposure can cause oxidative stress which can have negative consequences on animal cognition, reproduction and life expectancy. We investigated the current oxidative stress experienced by a mesic mouse species, the four striped field mouse,Rhabdomys dilectusthrough a heat wave simulation withad libwater and a more severe temperature exposure with minimal water. Wild four striped field mice were caught between 2017 and 2019. We predicted that wild four striped field mice in the heat wave simulation would show less susceptibility to oxidative stress as compared to a more severe heat stress which is likely to occur in the future. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers for oxidative damage, and superoxi...
Rodents use their forepaws to actively interact with their tactile environment. Studies on the ph... more Rodents use their forepaws to actively interact with their tactile environment. Studies on the physiology and anatomy of glabrous skin that makes up the majority of the forepaw are almost non-existent in the mouse. Here we developed a preparation to record from single sensory fibers of the forepaw and compared anatomical and physiological receptor properties to those of the hind paw glabrous and hairy skin. We found that the mouse forepaw skin is equipped with a very high density of mechanoreceptors; >3 fold more than hind paw glabrous skin. In addition, rapidly adapting mechanoreceptors that innervate Meissner’s corpuscles of the forepaw were several-fold more sensitive to slowly moving mechanical stimuli compared to their counterparts in the hind paw glabrous skin. All other mechanoreceptors types as well as myelinated nociceptors had physiological properties that were invariant regardless of which skin area they occupied. We discovered a novel D-hair receptor innervating a sma...
Mammalian Species, Aug 1, 2006
Journal of Morphology, Mar 10, 2016
Parasites & Vectors, Aug 15, 2014
Journal of Zoology, Jul 1, 2008
Frontiers in Ecology and Evolution, Jun 2, 2022
Mammalian Biology, Sep 1, 2013
Journal of Zoology, Feb 13, 2008
Frontiers in Zoology, 2014
General and Comparative Endocrinology, Jun 1, 2013
Meriones rex (King jird), Meriones libycus (Libyan jird), Acomys dimidiatus (Eastern spiny mouse)... more Meriones rex (King jird), Meriones libycus
(Libyan jird), Acomys dimidiatus (Eastern spiny
mouse), Acomys cahirinus (Egyptian spiny mouse), and
Dipodillus dasyurus (Wagner’s dipodil) are five species
of small rodents of the superfamily Muroidea with distributions
in Eastern Africa, Egypt, and the desert
regions of the Arabian Peninsula. Water is scarce in
these regions and may result in relatively lowdigestible
food. The aim of the present study is to
describe and compare the gastrointestinal tract morphology
and morphometry of these five species in order
to elucidate whether morphology is influenced by phylogeny
or dietary preference. Each segment of the gastrointestinal
tract of each species was macroscopically
examined and the length and basal surface area of
each segment was measured. Standard histologic procedures
were performed to determine a surface enlargement
factor to determine the mucosal luminal surface
area. A unilocular-hemiglandular stomach was
observed in all the species examined. The caeca of all
the species were long and arranged into a loose spiral
toward the caecal tip with the ileocaecal and caeco-colic
openings positioned close together. Two rows of oblique
folds could be observed in the proximal colon of all species
except in D. dasyurus which had longitudinal
folds. Morphometric analysis showed the largest stomach
in A. cahirinus and the largest caecum and colon
in M. libycus. All the species can be grouped in the
family Muridae in two subfamilies and similarities
were observed including the hemiglandular stomach
and relatively large caecum. It could be concluded that
phylogeny plays an important role in determining gastrointestinal
morphology while diet plays a subordinate
role in the desert rodents in the present study.