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.

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.

Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 2008. / The Bathyergidae are subterranean rodents endemic to Africa south of the Sahara. They are characterised by divergent diploid numbers that range from 2n=40 in Fukomys mechowi to 2n=78 in F. damarensis. In spite of this variation there is limited understanding of the events that shaped the extant karyotypes and in an attempt to address this, and to shed light on the mode and tempo of chromosomal evolution in the African mole-rats, a detailed analysis of both the autosomal and sex chromosome components of the genome was undertaken. In addition to G- and Cbanding, Heterocephalus glaber (2n=60) flow-sorted painting probes were used to conduct cross-species chromosome painting among bathyergids. This allowed the detection of a balanced sex chromosome-autosome translocation in F. mechowi that involved a complex series of rearrangements requiring fractionation of four H. glaber autosomes and the subsequent translocation of segments to sex chromosomes and to the autosomal partners. The fixation of this rare rearrangement has probably been favoured by the presence of an intercalary heterochromatic block (IHB) that was detected at the boundary with the translocated autosomal segment. Male meiosis in Cryptomys, the Fukomys sister clade, was investigated by immunostaining of the SCP1 and SCP3 proteins involved in the formation of the synaptonemal complex. This allowed confirmation of a Y-autosome translocation that is shared by C. hottentotus subspecies. We discuss reduced recombination between Y and X2 that seems to be heterochromatin dependent in the C hottentotus lineage, and the implications this holds for the evolution of a meiotic sex chromosome chain such as has been observed in platypus. By extending cross-species chromosome painting to Bathyergus janetta, F. damarensis, F. darlingi and Heliophobius argenteocinereus, homologous chromosomal regions across a total of 11 species/subspecies and an outgroup were examined using cladistic and bioinformatics approaches. The results show that Bathyergus, Georychus and Cryptomys are karyotypically highly conserved in comparison to Heterocephalus, Heliophobius and Fukomys. Fukomys in particular is characterised by a large number of rearrangements that contrast sharply with the conservative Cryptomys. The occurrence and fixation of rearrangements in these species has probably been facilitated by vicariance in combination with life history traits that are particular to these mammals.

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.

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 2005. / Zoology and Entomology / Unrestricted

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.

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.

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...

Microsatellites are repetitive DNA characterized by tandem repeats of short motifs (2 – 5 bp). High mutation rates make them ideal for population level studies. Microsatellite allele genesis is generally attributed to strand slippage, and it is assumed that alleles are caused only by changes in repeat number. Most analyses are limited to alleles (electromorphs) scored by mobility only, and models of evolution rarely account for homoplasy in allele length. Additionally, insertion/deletion events (indels) in the flanking region or interruptions in the repeat can obfuscate the accuracy of genotyping. Many investigators use microsatellites, designed for a focal species, to screen for genetic variation in non-focal species. Comparative studies have shown different mutation rates of microsatellites in different species, and even individuals. Recent studies have used reciprocal comparisons to assess the level of polymorphism of microsatellites between pairs of taxa. In this study, I investigated the evolution of microsatellites within a phylogenetic context, using comparisons within the rodent family Bathyergidae. Bathyergidae represents a monophyletic group endemic to sub-Saharan Africa and relationships are well supported by morphological and molecular data. Using mitochondrial and nuclear DNA, a robust phylogeny was generated for the Bathyergidae. From my results, I proposed the new genus, Coetomys. I designed species-specific genotyping and microsatellite flanking sequence (MFS) primers for each genus. Sequencing of the MFS provided direct evidence of the evolutionary dynamics of the repeat motifs and their flanking sequence, including rampant electromorphic homoplasy, null alleles, and indels. This adds to the growing body of evidence regarding problems with genotype scores from fragment analysis. A number of the loci isolated were linked with repetitive elements (LTRs and SINEs), characterized as robust phylogenetic characters. Results suggest that cryptic variation in microsatellite loci are not trivial and should be assessed in all studies. The phylogenetic utility of the nucleotide variation of the MFS was compared to the well-resolved relationships of this family based on the 12S/TTR phylogeny. Variation observed in MFS generated robust phylogenies, congruent with results from 12S/TTR. Finally, a number of the indels within the MFS provided a suite of suitable phylogenetic characters.