Mechanisms of tooth replacement distribute incongruently among extant gnathostomes (jawed vertebrates): a permanent tooth-generating dental lamina exists in chondrichthyans (cartilaginous fish) and tetrapods but not teleosts, whereas tooth shedding by basal hard tissue resorption occurs in tetrapods and teleosts but not chondrichthyans. Theories about the evolution of tooth development have been biased towards the chondrichthyan conveyor-belt replacement, since there has been no fossil evidence for the origin of osteichthyan (bony fish and tetrapods) tooth replacement until now. 3D virtual dissections with submicron-scale resolution, based on propagation phase contrast synchrotron microtomography (PPC-SRµCT), reveal the growth history of the dentitions of Andreolepis and Lophosteus, 423-Myr-old Silurian stem osteichthyans close to the common ancestor of tetrapods and teleosts. Their marginal jawbones and “tooth cushions” (possible homologues of coronoids) shed teeth by in situ cyclic basal resorption, the earliest examples of osteichthyan-style tooth replacement. The replacement cycles were site-autonomic, and occurred in broad irregular multi-row tooth fields, including at sites separated from the margin of the bone by intervening teeth, showing that the production of replacement teeth did not occur in a single deep dental lamina, but in pockets associated with each tooth, as in many teleosts. It suggests that the functionally and anatomically similar laminae of chondrichthyans and tetrapods are convergent. The marginal jaw bones of both genera carry an initial non-shedding dentition arranged in alternate transverse files, labial to the shedding tooth field, overgrown by later dermal ornament and probably not belonging to the oral domain, but bearing in vivo biting damage showing that they functioned as teeth. The most lingual of these odontodes have been resorbed apically and are overlain by shedding teeth. The first-generation teeth on the tooth cushions display basal resorption in Andreolepis, but semi-basal resorption in Lophosteus. The latter leaves a basal dentine ring from each tooth, implying only odontoclasts are involved in the semi-basal resorption, which is probably the first step towards evolving a site-specific resorption. The polarized displacement of each generation of resorption surfaces reflects the fact that the cyclic replacement, as well as the sequential addition of tooth sites, is closely related to bone growth. Resorption surfaces and growth arrest surfaces also record the life history and the replacement rate. These data provide unique insights into the origin of osteichthyan tooth replacement.

The role of temperature variation in organismal performance is understudied, but is critically important for understanding the response of biodiversity to climate change. To address this issue in herbivorous insects, I studied the direct and interactive effects of thermal regime (constant vs. fluctuating temperatures) and nutrition (dietary nitrogen) on gypsy moth (Lymantria dispar) performance under laboratory conditions. Predictions for differences between constant and fluctuating thermal conditions were derived from Jensen’s inequality, and artificial diets of differing nutritional quality were made by modifying nitrogen (casein) content. Larvae were reared in the laboratory under four temperature regimes (22°C constant, 22°C fluctuating (±6°C), 28°C constant, and 28°C fluctuating (±6°C)) and two diet treatments (high N, and low N). Gravimetric analyses were also conducted to calculate nutritional indices and assess the short-term effects of temperature and diet quality on fourth instar larvae growth efficiencies. Consistent with predictions from Jensen’s inequality, fluctuating thermal conditions significantly reduced larval performance in both sexes across ontogeny. Low quality diet also reduced performance, but interactions between diet and thermal regime were only found in early instars.

No description available.

No description available.

No description available.

Coastal fishes of the western North Atlantic, such as sciaenids and their competitors, support substantial commercial and recreational fisheries in waters that may vary widely in temperature, salinity, light intensity and spectral distrubution, and dissolved oxygen levels, yet their ecophysiological abilities to cope with such variability have received little attention. I therefore applied multidisciplinary comparative techniques to investigate aspects of the sensory and energetic ecophysiology of several sciaenid fishes and non-sciaenid competitors common in the western North Atlantic. Auditory brainstem response experiments demonstrated that sciaenid fishes have greatest auditory sensitivity at low frequencies that match their vocalizations. Based upon both anatomy and auditory bandwidths, most sciaenids appear to be hearing generalists that are likely sensitive to the particle motion components of aquatic sounds. Electroretinographic experiments revealed that the luminous sensitivities, temporal properties, and chromatic characteristics of the visual systems of phylogenetically-similar sciaenid fishes from different microhabitats, and those of phylogenetically-dissimilar piscivores from similar microhabitats, all correlated with lifestyle and ecology. The eyes of benthic and nocturnal fishes were typified by high luminous sensitivity, slow temporal resolution, and relative diel-invariance, consistent with foraging in dim photoclimates. By contrast, the eyes of pelagic diurnal piscivores had comparatively lower luminous sensitivity, higher temporal resolution, and exhibited higher diel variation, consistent with specific diurnal light niches. Accordingly, visually-foraging diurnal piscivores may be disadvantaged in eutrophied, turbid waters characteristic of many modern estuaries. Intermittent-flow respirometry experiments revealed that the majority of sciaenid fishes had resting and active metabolic rates similar to those of most teleost fishes but significantly lower than high-demand species such as tunas. However, the metabolic rates of kingfishes (Menticirrhus sp.) were significantly higher than other sciaenids, but significantly lower than those of tunalike fishes. Estimates of standard metabolic rate from power performance curves fitted to active metabolic rate data did not differ significantly from experimentally-derived measurements in static chambers, validating the experimental approach. Data from these chapters were analyzed with linear repeated measures and nonlinear mixed effects models that considered repeated measurement of subjects, modeled within-individual correlations, and the included random factors that improved the scope of inference. Although not novel approaches, these methods demonstrate quantitative advancements for future analyses of physiological data comprised of multiple measurements taken from individual experimental subjects. Collectively, the results of this dissertation underscore the potential power and utility of physiological techniques to provide a wide variety of information that may complement more traditional techniques used in fisheries science, particularly when coupled with appropriate analytical strategies. Sciaenid fishes are model organisms for investigations of the links between form, function, and the environment in coastal ecosystems.

This thesis presents two novel algorithms for the evolutionary optimisation of agent populations through divergent search of low dimensional phenotypic landscapes. As the eld of Evolutionary Robotics (ER) develops towards more complex domains, which often involve deception and uncertainty, the promotion of phenotypic diversity has become of increasing interest. Divergent exploration of the phenotypic feature space has been shown to avoid convergence towards local optima and to provide diverse sets of solutions to a given objective. Novelty Search (NS) and the more recent Multi-dimensional Archive of Phenotypic Elites (MAP-Elites), are two state of the art algorithms which utilise divergent phenotypic search. In this thesis, the individual merits and weaknesses of these algorithms are built upon in order to further develop the study of divergent phenotypic search within ER. An observation that the diverse range of individuals produced through the optimisation of novelty will likely contain solutions to multiple independent objectives is utilised to develop Multiple Assessment Directed Novelty Search (MADNS). The MADNS algorithm is introduced as an extension to NS for the simultaneous optimisation of multiple independent objectives, and is shown to become more e ective than NS as the size of the state space increases. The central contribution of this thesis is the introduction of a novel algorithm for rapid and thorough divergent search of low dimensional phenotypic landscapes. The Spatial, Hierarchical, Illuminated NeuroEvolution (SHINE) algorithm di ers from previous divergent search algorithms, in that it utilises a tree structure for the maintenance and selection of potential candidates. Unlike previous approaches, SHINE iteratively focusses upon sparsely visited areas of the phenotypic landscape without the computationally expensive distance comparison required by NS; rather, the sparseness of the area within the landscape where a potential solution resides is inferred through its depth within the tree. Experimental results in a range of domains show that SHINE signi cantly outperforms NS and MAP-Elites in both performance and exploration.

Meiotic recombination plays a fundamental role in many sexually reproducing species. Recombination shuffles the genetic material during the first meiotic cell division resulting in new combinations of alleles within each chromosome. In many organisms, the rate of recombination is not uniform across the genome but consists of so called hotspots where the recombination rate is remarkably higher than the genome average. In mammals, the regulation and location of recombination hotspots is regulated by a gene called PRDM9. Many nonmammalian animals, like birds, lack this gene and the precise mechanism for recombination rate regulation is still unknown. Previous findings in passerine birds have observed an association between recombination rate and a genomic feature known as CpG islands (CGIs). CGIs are often located in promoter regions of genes and depending on their methylation status constitute accessible chromatin regions. It has therefore been suggested that the proteins involved in the regulation of recombination have better access to less condense chromatin regions. In this study, I tested if the association between recombination rate and CGIs found in passerine birds is also true in chicken. I also tested if methylation levels of CGIs play a role in recombination rate regulation in chicken. To this end, I used previously published data for CGI locations and a methylation map in chicken, and unpublished data of recombination rate estimates. I found that the association between recombination rate and CGIs observed in passerine birds extends to chicken, suggesting that this is an ancestral trait in birds. I did not, however, find a negative association between methylation levels and recombination rate as hypothesised based on a relationship between methylation level and chromatin accessibility. This suggests that DNA methylation level at CGIs is not a strong determinant of recombination in chicken, although there may be some workflow artefacts or unknown factors remaining in my analysis obscuring the relationship between these two variables.

No description available.

No description available.