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Brains of African mole-rats in numbers: Data for testing the social brain hypothesis
Kverková, Kristina ; Němec, Pavel (advisor) ; Pavelková, Věra (referee)
The social brain hypothesis (SBH) posits that complex social environments exert a major selection pressure driving the evolution of large brains and intelligence. The hypothesis was first proposed to explain the remarkable cognitive abilities of primates and has since been extended to other vertebrate groups and gained a substantial popularity. Nevertheless, the empirical support is equivocal in virtually every group where the hypothesis has been tested. In this thesis, the SBH is tested in the African mole-rats (Bathyergidae). Mole-rats share a subterranean mode of life and similar ecologies while covering the whole social spectrum, from solitary to "eusocial". The number of brain neurons is considered a better proxy for intelligence than relative or absolute brain size. Therefore, a novel approach, the isotropic fractionator, was used to estimate the total number of neurons and other cells in five brain parts (olfactory bulbs, cerebral cortex, cerebellum, diencephalon and basal ganglia, brain stem) of eleven bathyergid species. This simultaneously allows for examining if and how mole-rats differ from other rodents with respect to brain cellular scaling rules. We found that, contrary to expectations, mole-rats generally conform to these rules, with a few exceptions. They tend to have higher...
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Brains of African mole-rats in numbers: Data for testing the social brain hypothesis
Kverková, Kristina ; Němec, Pavel (advisor) ; Pavelková, Věra (referee)
The social brain hypothesis (SBH) posits that complex social environments exert a major selection pressure driving the evolution of large brains and intelligence. The hypothesis was first proposed to explain the remarkable cognitive abilities of primates and has since been extended to other vertebrate groups and gained a substantial popularity. Nevertheless, the empirical support is equivocal in virtually every group where the hypothesis has been tested. In this thesis, the SBH is tested in the African mole-rats (Bathyergidae). Mole-rats share a subterranean mode of life and similar ecologies while covering the whole social spectrum, from solitary to "eusocial". The number of brain neurons is considered a better proxy for intelligence than relative or absolute brain size. Therefore, a novel approach, the isotropic fractionator, was used to estimate the total number of neurons and other cells in five brain parts (olfactory bulbs, cerebral cortex, cerebellum, diencephalon and basal ganglia, brain stem) of eleven bathyergid species. This simultaneously allows for examining if and how mole-rats differ from other rodents with respect to brain cellular scaling rules. We found that, contrary to expectations, mole-rats generally conform to these rules, with a few exceptions. They tend to have higher...
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Sensory abilities in food localization in four species of African mole-rats with diverse social organization
VITÁMVÁS, Miloš
Until recently, it was assumed that African mole-rats search for food randomly, as it is in concordance with Aridity food distribution hypothesis. However, recent studies indicate that some subterranean rodent species including mole-rats could be able to use plant chemicals (kairomones) for food localization. In my master thesis I conducted a battery of experiments on four mole-rat species to prove, that these species also posses the ability of kairomone guided foraging independently of their social organization.
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Poikilothermic traits in Mashona mole-rat (Fukomys darlingi). Reality or myth?
ZEMANOVÁ, Milada
The African mole-rats is a mammalian family well known for a variety of ecophysiological adaptations for strictly belowground life. The Mashona mole-rat (Fukomys darlingi) is supposed to have strong poikilothermic traits, because it is not able to maintain a stable body temperature at ambient temperatures below 20°C. In our study, we measured resting metabolic rate and body temperature of Mashona mole-rats across a gradient of ambient temperatures to test its poikilothermic traits. Tested mole-rats show typical mammalian pattern in resting metabolic rates. And their body temperature was stable at ambient temperatures from 10 to 25°C. We thus cannot confirm poikilothermic traits in this species.
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Vibrational communication of subterranean rodents
HROUZKOVÁ, Ema
This PhD. thesis focuses on the vibrational communication of subterranean mammals, in particular, vocal communication of bathyergids (Heliophobius argenteocinereus, Fukomys mechowii, Fukomys darlingi) and seismic communication of Tachyoryctes. We recorded and analyzed the vocalization of three species and discussed the physical parameters of their vocalization in relationship to the special underground acoustic environment. Moreover, social systems of African mole-rats range from solitary to eusocial and thus our results enabled us to discuss the influence of sociality on vocal repertoire richness and its composition. Long distance communication possesses many challenges in underground environments; the only effective mean is seismic communication. We described for the first time seismic signaling in Tachyoryctes and proposed its function.
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Ecology and activity of mesic Afrotropic mole-rats
LÖVY, Matěj
This Ph.D. thesis focuses on the ecology and activity of mesic Afrotropic mole-rats. In particular, ecological characteristics in habitats of two mole-rat species with different social system, the solitary Heliophobius argenteocinereus and social Fukomys whytei, were analysed in an area of sympatry and the results are discussed in relation with available ecological data on other species. Two studies bring to light novel data on the ecology and behaviour of the free-living largest social bathyergid, the giant mole-rat Fukomys mechowii, especially in relation to ecological characteristics in its natural habitat, burrow system architecture, kin structure and spatial and temporal activity patterns. In the final study, new data on the field metabolism of the silvery mole-rat H. argenteocinereus are presented. These new findings are discussed in further detail and expand upon existing explanations for low resting metabolism in subterranean rodents and the differences in field metabolism in relation to seasonality of habitat.
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The Thermoregulatory Abilities in a Mole-rat \kur{Fukomys darlingi} and its Development in Pups
ZEMANOVÁ, Milada
The oxygen consumption and body temperature were measured in adults and pups of a social Mashona mole-rat(Fukomys darlingi)to test poikilothermic traits in this species and effect of presence of adults on pup´s thermoregulation abilities. The adult´s resting metabolic rate was 0.76 {$\pm$} 0.20 mlO2g-1hod-1 in the thermoneutral zone 27-34°C. We did not confirm poikilotermic traits in this species, because body temperature was stable (33.0 {$\pm$} 0.5°C) at low ambient temperatures. The pups started to thermoregulate in age of one month and they are able to maintain stable body temperature very late in age of three months. My results indicate that presence of adults is necessary for thermoregulation of pups.
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The Thermoregulatory Abilities in a Mole-rat \kur{Fukomys darlingi} and its Development in Pups
ZEMANOVÁ, Milada
The oxygen consumption and body temperature were measured in adults and pups of a social Mashona mole-rat(Fukomys darlingi)to test poikilothermic traits in this species and effect of presence of adults on pup´s thermoregulation abilities. The adult´s resting metabolic rate was 0.76 {$\pm$} 0.20 mlO2g-1hod-1 in the thermoneutral zone 27-34°C. We did not confirm poikilotermic traits in this species, because body temperature was stable (33.0 {$\pm$} 0.5°C) at low ambient temperatures. The pups started to thermoregulate in age of one month and they are able to maintain stable body temperature very late in age of three months. My results indicate that presence of adults is necessary for thermoregulation of pups.
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Exploratory and spatial learning abilities in two African mole-rats with different social system.
MAZOCH, Vladimír
The goal of this study was to examine differences in the exploratory activity, spatial learning and memory between two strictly subterranean rodents with different social systems, solitary silvery mole-rat (Heliophobius argenteocinereus) and social giant mole-rat (Fukomys mechowii) in a maze resembling natural burrows. Although the giant mole-rats showed better performance in most of the parameters of the test, this could not be easily explained by superior learning abilities of social species. The differences found could be more attributed to different motivation in both species. The solitary mole-rat was remarkably more cautious and moved with lower velocity, spent more time in the maze, made more errors and traveled a longer path before reaching the reward box.
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