No description available.

<p>This thesis is focused on the heparan sulphate (HS) structure from blind mole rat liver. HS is a glycosaminoglycan that is produced as a proteoglycan, in which linear polysaccharide chains are attached covalently to a protein core. Proteoglycans are widespread molecules in the body and have many important physiological functions. HS is synthesized as a polymer of alternating glucuronic acid and N-acetylglucosamine units. Parts of the polymer are subsequently modified by N-deacetylation /N-sulphation of the glucosamine units, C-5 epimerization of glucuronic acid to iduronic acid and O-sulphation at various positions.</p><p>The mole rats are from Israel and are of the Spalax ehrenbergi superspecies. Spalax Judaei (S60) has 60 chromosomes and Spalax Galili (S52) has 52 chromosomes. They are both completely blind and spend their entire life underground in hypoxic conditions. Spalax Galili (S52) inhabits the cool-humid Upper Galilee Mountains and Spalax Judaei (S60) inhabits the warm-dry southern regions. There is no current information about the heparan sulphate structure of these animals.</p><p>The two blind mole rats (S52 and S60) were metabolically labelled with [3H] Glucosamine. The animals were sacrificed and the organs were taken and frozen. The liver was chosen for the purpose of my project.</p><p>The HS structure was studied using various chromatographic methods such as ion-exchange and gel filtration. Structural analysis of HS indicated that the size of HS from the liver was the same in both species. However, the domain structure differed between the two animals, particularly with regard to sample S52(1) which had obvious differences. This leads to the study of the heparanase cleavage sites. Disaccharide composition analysis identified varying proportions of disaccharide species in S52 and also the possibility of an unknown disaccharide species.</p>

This thesis is focused on the heparan sulphate (HS) structure from blind mole rat liver. HS is a glycosaminoglycan that is produced as a proteoglycan, in which linear polysaccharide chains are attached covalently to a protein core. Proteoglycans are widespread molecules in the body and have many important physiological functions. HS is synthesized as a polymer of alternating glucuronic acid and N-acetylglucosamine units. Parts of the polymer are subsequently modified by N-deacetylation /N-sulphation of the glucosamine units, C-5 epimerization of glucuronic acid to iduronic acid and O-sulphation at various positions. The mole rats are from Israel and are of the Spalax ehrenbergi superspecies. Spalax Judaei (S60) has 60 chromosomes and Spalax Galili (S52) has 52 chromosomes. They are both completely blind and spend their entire life underground in hypoxic conditions. Spalax Galili (S52) inhabits the cool-humid Upper Galilee Mountains and Spalax Judaei (S60) inhabits the warm-dry southern regions. There is no current information about the heparan sulphate structure of these animals. The two blind mole rats (S52 and S60) were metabolically labelled with [3H] Glucosamine. The animals were sacrificed and the organs were taken and frozen. The liver was chosen for the purpose of my project. The HS structure was studied using various chromatographic methods such as ion-exchange and gel filtration. Structural analysis of HS indicated that the size of HS from the liver was the same in both species. However, the domain structure differed between the two animals, particularly with regard to sample S52(1) which had obvious differences. This leads to the study of the heparanase cleavage sites. Disaccharide composition analysis identified varying proportions of disaccharide species in S52 and also the possibility of an unknown disaccharide species.

The significance of vocal communication in subterranean rodents was confirmed. In this study I tested whether vocalization of the Mashona mole-rats (Fukomys darlingi) differs individually and what information about signaller are these mole-rats able to obtain using only acoustic cues.

Large individual differences in cooperative contributions are common within animal societies such as cooperative breeders, where helpers care for offspring which are not their own. Understanding this variation has been a major focus in behavioural ecology and while evidence has shown that individuals are capable to adaptively adjust their cooperative behaviours, the physiological mechanisms underlying such adjustments remain poorly understood. Steroid hormones are prominent candidates to regulate cooperative behaviours due to their ability to integrate internal physiological state and environmental stimuli to produce an adaptive behavioural response. In this thesis, I investigate the effects of two steroid hormones, Cortisol (CORT) and Testosterone (T), in the regulation of cooperative behaviours in the Damaraland mole-rat (Fukomys damarensis). Because these hormones are susceptible to both modulate and be modulated by cooperative contributions, I experimentally tested both sides of this relationship. I show that, despite the absence of correlation between CORT and T and cooperative contributions, experimental increases of cooperative contributions elevate CORT levels, but not T (Chapter 3). Additionally, experimental increases of CORT levels in female helpers raised their cooperative contributions by more than one half demonstrating the regulatory effect of CORT on cooperative behaviours (Chapter 4). As breeding opportunities are likely to affect cooperative contributions and because T is a likely candidate to mediate a trade-off between future reproduction and current cooperation, I tested the effects of experimental increases of T levels in female helpers. I show that such elevations have no measurable effect of aggression, dispersal tendencies (both important to attain a breeding position) or cooperative contributions (Chapter 5). Taken together, the results of this thesis demonstrate that CORT can both respond to and regulate cooperative behaviours and suggest that this hormone may play a major role in the adaptive regulation of cooperative behaviour.

Social behavior of some species of African mole-rats makes them interesting object of study. Members of multigenerational families were only one pair breeds collectively work on building of their burrow system and obtaining food. Distribution of activity during the day in individual family members may give us a clue of how they manage their work. However, studies monitoring mole-rats in their natural environment are scarce and usually carried out on low number of individuals. Present study deals with outside-nest activity of 16 free-living Ansell´s mole-rats using data obtained by automatic radio-telemetry - method which was used in radio-tracking of mole-rats for the first time. It reveals differences in activity pattern of individual mole-rats and examines how they relate to body mass, sex, reproductive status and affiliation to a family and test whether individuals of the same family tend to be synchronized in their outside nest activity.

African mole-rats (Bathyergidae) are subterranean hystricomorph rodents offering an excellent system with which to test theories relating to the evolution and maintenance of sociality in mammals. The aridity food distribution hypothesis (AFDH) suggests that, within the bathyergids, sociality has evolved in response to patterns of rainfall, its effects on food distribution, and the subsequent costs and risks of foraging and dispersal. Here, in the first detailed study of burrow architecture in a social mole-rat species, with data from 32 burrows, we show that in the giant mole-rat Fukomys mechowii, burrow fractal dimension increases with colony size and is higher during the rainy season than during the dry season. The mass of food in the burrow increases with fractal dimension and is higher during the rainy season than during the dry season. These results link for the first time colony size, burrow architecture, rainfall and foraging success and provide support for two assumptions of the AFDH, namely that (1) in arid conditions burrowing may be severely constrained by the high costs of digging; and (2) the potential risks of failing to locate food may be mitigated by increases in colony size. It was also fundamental in this study to assess whether the Fukomys mechowii is (1) An aseasonal or seasonal breeder (2) To investigate whether non-reproductive female giant mole-rats exhibit induced or spontaneous ovulation and finally (3) To estimate the age variation and sexual dimorphism of this little studied giant mole-rat species. Thus in a field study that involved the complete excavation of 32 burrow systems with a mean colony size of 9.9 individuals (range 7-16), it was evident that Fukomys mechowii is a cooperatively breeding mole-rat exhibiting a reproductive division of labour in which usually one, or occasionally two, females are responsible for procreation. Pregnant reproductive females were found throughout the study period (September 2005 until June 2006), supporting preliminary evidence that reproduction occurs throughout the year. Of the 32 colonies sampled, 14 of 18 (87.5%) in which the reproductive female could be identified as pregnant contained a single reproductive female, while four (12.5%) had two females breeding simultaneously (plural breeding). The population sex ratio was skewed towards females at 1:1.46. Autopsy of pregnant reproductive females (n=18) revealed that the production of two (10/18 pregnancies) or three (7/18) offspring was the norm, with one case of four embryos being present. These new data increase our fragmentary knowledge of the natural history of this little studied species. Six non-reproductive females were removed from their natal colonies and housed individually without a male for a period of 12 weeks as a control group. They were then subsequently housed for a further 6 weeks as experiment 1, on their own before being allowed non-physical contact in experiment 2, with a mature adult male for a further 6 weeks. The non-reproductive females were given a further period of isolation for a month prior to being physically paired with vasectomized males, in experiment 3. Urine was collected every second day for all three experiments and urinary progesterone profiles were generated. The progesterone values measured during the first part of Experiment 2 and 3 were markedly higher than those measured during the first part of Experiment 1 (Z= -2.201, p=0.028 for both comparisons), however, this was not significant after Bonferroni correction. Similarly progesterone values tended to be elevated during the second phase of Experiment 2 and 3 but not significantly so (Experiment 1 vs. 2: Z=-1.782, p=0.075, Experiment 1 vs. 3: Z=-2.201, p=0.028). Thus, chemical or physical stimulation by a male does not appear to be necessary for ovulation in female giant mole-rats. The giant mole-rat is a spontaneous ovulator. Due to difficulties in estimating absolute age in mammals, different methods for its estimation have been proposed, and among these, the degree of molar eruption and wear are considered to be one of the most reliable indicators of relative age. Consequently, maxillary molar tooth-row eruption and wear were used to assign individuals of the giant mole-rat, Fukomys mechowii (Peters, 1881) from two geographically proximal and ecologically similar localities in the Copper-belt Province of Zambia to 9 relative age classes. These were in turn used to assess the nature and extent of sexual dimorphism and age variation in this little-studied social mole-rat based on cranial morphometric data, reference to body mass and a series of both univariate and multivariate statistical analyses. Both univariate and multivariate analyses showed morphological differences between individuals of age classes 1–3 and those of age classes 5–9, while individuals of age class 4 were intermediate between these age class groupings, suggesting that this age class lies at a point on a hypothetical growth curve where it begins to stabilize. The analysis of the nature and extent of sexual dimorphism revealed its absence in the younger individuals of age classes 1–4 and its presence in older age classes 5–9. These results may allow an insight into our understanding of the population social structure, and reproductive strategies in the giant mole-rat. In conclusion, it is worth mentioning that; (1) A number of studies have examined burrow architecture, although not necessarily fractal dimensions in the Bathyergidae but the majority of these have concentrated on solitary species in which when there is plural occupancy it is during the breeding season or when the mother has a litter. This study is thus the first to examine in detail the dynamic nature of social mole-rat burrows, with respect to seasonal changes. The burrow fractal dimension is a good indication of the mole-rats ability to burrow to find food and thus results support the critical assumption which underlies the aridity food distribution hypothesis. The results accord well with previous data in social mole-rats indicating that larger colonies have greater survival and link colony size, burrow architecture and foraging success for the first time; (2) the giant mole-rat is an aseasonal breeder which in a few instances can have two queens per colony; (3) the giant mole-rat is a spontaneous ovulator and finally (4) the giant mole-rat Fukomys mechowii exhibits a sexual dimorphism amongst its older age classes 5-9. Suggesting that there are different growth curves in males versus females, whereby males attain much larger size (skull size and body mass) than females after puberty and finally intimating that opportunistic mating competition among males is very high. / Thesis (PhD)--University of Pretoria, 2011. / Zoology and Entomology / Unrestricted

Naked mole-rats live in large colonies and exhibit a strict reproductive hierarchy. Each colony has 1 breeding female and 1-3 breeding males; all other individuals are non-reproductive subordinates. Subordinates show a remarkable lack of sex differences in behavior and anatomy, but can become reproductive if removed from the colony. The striated perineal muscles and their innervating motoneurons, which are sexually dimorphic in all other mammals examined, are not dimorphic in subordinate naked mole-rats. Here I asked whether sexual differentiation of this neuromuscular system occurs when subordinates become breeders. Sex differences in perineal motoneurons were not observed, regardless of social status. To my surprise counts of motoneurons in Onuf’s nucleus were increased in breeders of both sexes. This was accompanied by a reciprocal decrease in cells in Onuf’s nucleus that were characterized by small soma size. The neuronal changes correlate with increased perineal muscle volumes in breeders. Although not exhibiting typical motoneuron morphology, some small cells fit a neurochemical or functional definition of a motoneuron. I propose that small cells are recruited to the pool of large Onuf’s nucleus motoneurons when subordinate naked mole-rats become breeders. I then looked at naked mole-rats of varying status (subordinates, paired animals that have never reproduced, intact breeders, and gonadectomized breeders) to determine which cues elicit changes in perineal muscles and small cells in Onuf’s nucleus. I found that pairing is sufficient to cause decreases in the population of small cells in Onuf’s nucleus, while production of litters is necessary for increasing in perineal muscle size. The gonads were not necessary to maintain changes in small cells or perineal muscles. I hypothesized that the lack of sex differences in naked mole-rats might be related to their unusual social structure. To test this, I compared the genitalia and perineal muscles in three African mole-rat species: the naked mole-rat, the solitary silvery mole-rat, and the Damaraland mole-rat, a species considered to be eusocial, but with less reproductive skew than naked mole-rats. My findings support a relationship between social structure, mating system, and sexual differentiation.

The magnetic orientation was study in several species of rodents. Aim of this work was verify magnetic sense in two species of subterranean rodents: the giant mole-rat and the silvery mole-rat. A spontaneous directional preference in the magnetic field was tested in circular arena.

Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Science, 2000.