The social mole-rats have often been typecast as extreme examples of mammalian sociality. With their pronounced reproductive skew, status-related contrasts in lifespan and morphology, and the suggestion of a division of labour amongst helpers, mole-rat societies have repeatedly been likened to the structurally complex societies of some eusocial insects. However, because few studies of mole-rats have quantified individual variation in growth and behaviour across long periods of development, it has remained unclear the extent to which mole-rat societies, and the features of individuals within them, should be considered unique amongst social vertebrates. In this thesis, I examine life history variation in Damaraland mole-rats Fukomys damarensis from three perspectives- growth, behaviour, and ageing- to explore how individual developmental trajectories contribute to, and are influenced by, the structure of mole-rat societies. First, I use a large longitudinal dataset to test for the presence of behavioural specialisation in non-breeding mole-rat helpers. I find no indication of individual specialisation in cooperative activities. Instead, individual differences in helping behaviour are largely the result of age-related changes in the extent to which individuals commit to all forms of helping (Chapter 3); refuting the notion of helper castes. I then focus on the variation in growth across non-breeders, developing a novel biphasic model to accurately quantify sex differences in growth and explore the influence of social effects on growth trajectories (Chapter 4). Despite the proposition of intense intrasexual competition in mole-rat societies, there was no clear signature of sex-specific competition on helper growth trajectories. A more conspicuous form of socially-mediated growth in mole-rats is the secondary growth spurt displayed by females that have acquired the dominant breeding position, causing them to become larger and more elongated. By experimentally controlling reproduction in age-matched siblings, I show that rather than being stimulated by the removal from reproductive suppression, this adaptive morphological divergence is achieved through a lengthening of the lumbar vertebrae when breeding is commenced (Chapter 5). With contrasts in size and shape following the acquisition of the breeding role, this status-related growth pattern shares similarities with growth in naked mole-rats and other social vertebrates. Breeders also show a twofold greater lifespan than non-breeders in Fukomys mole-rats, prompting the suggestion that the transition to dominance also sets individuals onto a slower ageing trajectory. To date, there is little evidence to support a physiological basis to lifespan extension in breeders. This assertion is bolstered by the absence of longer telomeres or slower rates of telomere attrition in breeding females compared to non-breeding females residing in groups (Chapter 6), each of which might be expected if breeders age more slowly. I argue that previous studies exploring status-related ageing in captive Fukomys mole-rats have overlooked the importance of demographic processes (and associated behavioural influences) on mortality schedules. Irrespective of the proximate basis of the longer lifespan of breeders, at an interspecific level the social mole-rats are unusually long-lived for their size. A recent large-scale comparative analysis concluded that prolonged lifespan is a general characteristic of all mammalian cooperative breeders, but this conclusion is premature, as in most of the major clades containing both cooperative and non-cooperative species there is no consistent trend towards lifespan extension in cooperative species (Chapter 7). In the case of mole-rats, it seems more likely that their exceptional longevity arises principally from their subterranean habits and related reductions in extrinsic mortality. Overall, these findings demonstrate that cooperative breeding has important consequences for individual life histories, but there is no strong basis for the claim that Damaraland mole-rat societies are markedly different in form than other cooperative breeding societies.

The genus <i>Gluconobacter</i> is known to carry out limited oxidations using the NAD(P)-independent membrane-bound dehydrogenases in which the products are released back to the medium. Reports of further limited oxidations of these primary oxidation products by <i>Gluconobacter</i> in single step or sequential oxidations by secondary dehydrogenases are also published. The objective of this project was to evaluate the nature of one primary (sorbitol) dehydrogenase and one secondary (sorbose) dehydrogenase because of their importance in Vitamin C production. My hypotheses were that sorbitol (the primary) dehydrogenase is constitutive, while sorbose (the secondary) dehydrogenase is inducible. Six <i>Gluconobacter</i> strains from three different species grew on plates containing 50/0 sorbose, indicating their ability to oxidize sorbose thus possessing a secondary dehydrogenase. When four strains were tested for their ability to carry out the sequential oxidation of sorbitol and then sorbose on media containing growth-limiting sorbitol concentrations, three strains showed possible biphasic growth. However, thin layer chromatography of culture media did not support sequential sorbitol and sorbose oxidation. F erricyanide assays for sorbitol and sorbose dehydrogenases from membrane fractions isolated from cells grown on glycerol, sorbitol, or sorbose showed that sorbitol dehydrogenase activity in all four strains (three species) tested was always present (constitutive) and its specific activity was always enhanced by growth on sorbose. Membrane fractions showed no or very low constitutive sorbose dehydrogenase activity and no evidence that this secondary dehydrogenase was induced. / Master of Science

The instantaneous mortality rate (M) is an important parameter in elasmobranch management and conservation, but is difficult to estimate directly. Thus, indirect estimates based on relatively easily obtained life history parameters are commonly used. Many indirect methods incorporate one or more parameters from the von Bertalanffy growth model (VBGM), which is often criticized for its inability to describe changes in growth associated with maturity. The Lester growth model (LGM) is a biphasic alternative to the VBGM that incorporates trade-offs between reproduction, growth, and survival, and may therefore more accurately estimate M. I used published data from 29 elasmobranch species to compare the performance of the LGM to four conventional growth models and nine conventional methods for indirectly estimating M. For three species (Heterodontus portusjacksoni, Rhizoprionodon taylori, and Carcharhinus limbatus), I obtained direct estimates of M to evaluate the accuracy of indirect M methods. According to AICc, the LGM was the best fitting model for 80.8% of datasets. Using one-sample t-tests, I found that five indirect M methods (two of which are dependent on the LGM) consistently generated estimates of M that were in close agreement with direct estimates. The most common methods in elasmobranch literature appear to be overestimating M by factors of 1.34 – 1.91. However, further research is needed to verify these results across a wider range of species. Overall, I recommend using the LGM to describe the lifetime growth of sharks, and estimating M by averaging across five indirect methods.