Interactions between non-native yabbies (Cherax albidus) and indigenous marron (Cherax tenuimanus) in the south-west of Western Australia are not well understood. While there is abundant evidence to suggest that invasive freshwater crayfish are detrimental to native species, the nature and degree of impact on marron populations by exotic yabbies remains unclear. Researchers have hypothesized that invasive species make faster and more appropriate use of information about their environment than native species. This greater behavioural plasticity can result in displacement of indigenous species, successful colonisation by invaders, and subsequent disturbance to natural ecosystems and representative biodiversity. / The research presented in this thesis examines the behavioural responses of an indigenous crayfish (C. tenuimanus) and an invasive crayfish (C. albidus) to waterborne odours derived from food, alarm sources and finfish predators. This study was undertaken to assist in the understanding of predatory and competitive interactions between indigenous and non-indigenous crayfish and fish predators, with particular relevance to Western Australia. Predation and competition are major forces influencing community structure in ecosystems; therefore knowledge of competitive and predatory interactions will be of benefit when considering future translocation policies. / Behavioural trials were conducted in two culture systems (54 L aquaria and a 70,000 L mesocosm), where marron and yabbies were exposed to a range of water-borne odours from finfish predators (silver perch and Murray cod), with and without competition from conspecific and heterospecific crayfish. A number of variables likely to influence crayfish behaviour were investigated: strength of chemical odour; crayfish size, gender, diurnal and nocturnal activity patterns; predator size; prior-residence; suitable habitat/shelter; and feed availability. / A key innovation in this research was the high replication in the aquarium-based observation trials using a Latin Cube design, which resulted in greater statistical strength and lower variability. More importantly, this research deviated from the tradition of exclusively using the ‘individual crayfish’ approach for odour-detection experiments and tested these results in a 70,000 L communal observation tank. This was an important development in crayfish behavioural experimentation, particularly as several key findings from the individual crayfish approach were confirmed in a multi-species environment. / Results from this study supported the hypothesis that invasive crayfish species make more appropriate use of a wider range of information about their environment than native crayfish species. Yabbies were found to possess behavioural characteristics not present in marron, such as clearer behavioural modifications to food and heterospecific odour, and cautionary behaviour in the presence of odour from a finfish predator. During simulated daylight conditions, marron displayed behaviours conducive to predation that were not present in yabbies, including less time spent in shelter and more time spent in locomotory activity. However, during specialised night-time observational studies developed during this research, these differences were not evident. This would not seem to be an unusual result, given that crayfish naturally forage at night and become more active; however, it may have important implications for future behavioural studies of crayfish, indicating a bias associated with day-time approaches. Crayfish size also played a role in behavioural modifications to water-borne odours. Larger marron displayed clearer changes in behaviour and were more responsive to heterospecific alarm odour than juveniles. Furthermore, juveniles of both species were more active than adults and sub-adults. / The expansion of the yabby population into Western Australian habitats occupied by marron has been facilitated through translocation for aquaculture, and biological characteristics of the species, some of which are typical of other invasive crayfish species including: tolerance of a variety of conditions; rapid growth; early sexual maturity; burrowing to escape drought and predation; capable of multiple spawns in a growth season; and aggressiveness. Another characteristic of invasive crayfish species also shared by yabbies, as supported by the results of this study, is high behavioural plasticity. / Although marron do not share the same level of behavioural plasticity found in yabbies, their larger body size increases their success in competitive interactions. The comparatively smaller body size of yabbies may be the major factor limiting their population expansion in the presence of marron, especially in water-bodies where shelter is a limited resource. / Marron are an important endemic species in Western Australia, but their conservation is threatened by competition and predation from exotic species. The research presented in this thesis indicates that invasive yabbies are more receptive to chemical stimuli and better equipped to respond to predation risk than marron. This information will be of benefit when considering future translocation policy in Western Australia and highlights the need for a cautious approach to species introductions.

A local integrated pulp and paper Kraft mill had come under pressure from the local communities and mill personnel to reduce the odours that were perceived to be generated at the Farm Dams and irrigation farm situated adjacent to the mill. The typical odours associated with Kraft mills are due to the generation of four reduced sulphur compounds such as hydrogen sulphide (H2S), methyl-mercaptan (CH3SH), dimethyl-sulphide (CH3)2S and dimethyl-disulphide (CH3)2S2. These compounds are collectively referred to as Total Reduced Sulphur (TRS) components which are generated as a direct result of the Kraft pulping and chemical recovery process. These components can either be in the gaseous or aqueous phase depending on the characteristics of the effluent. Gaseous and aqueous TRS profiling of the mill indicated that hydrogen sulphide (H2S) was the main odour component generated and emitted from the Clarifiers and the Treated Effluent Transfer Sump (TETS) at the effluent treatment plant. The hydrogen sulphide (H2S) emission levels were affected by process upsets, sludge removal frequencies, chemical composition of the effluent, Sulphate Reducing Bacteria (SRB) activity, pH and temperature fluctuations. Treatment options such as pH control using slaked lime, dosing of biocides, addition of biomodifiers and/or a sulphate reduction inhibitor were investigated. The use of slaked lime, Ca(OH) 2, for pH control was not practical due to continuous pH fluctuations, increasing the pH would increase the scaling tendencies of the effluent and would also affect the soil cation-anion exchange properties of the irrigated farm land. The use of non-oxidising biocides was effective in reducing SRB activity between 99.2% and 99.8% at dosages between 4 mg/l and 25 mg/l. However, the use of biocides was not considered as a long term treatment option due to the various disadvantages such as the stability of the biocides at fluctuating pH and temperatures, half-life, environmental accumulation, toxicity and costs. The aqueous H2S level was reduced by 79% using different combinations of biomodifiers (nitrates, nitrites, molybdenum). Increasing the dosages of the biomodifiers (> 500mg/l) would be required to increase the reduction of H2S levels by more than 79%. The increased dosages would significantly increase the cost of the treatment programme. The accumulation of nitrates, nitrites and molybdenum could affect the soil texture, cation-anion exchange capacity, permeability, Sodium Absorption Ratio (SAR) and nutrient availability. A more environmentally friendly and cost effective treatment was found using sodium nitrate (biomodifier) together with AQ (sulphate reduction inhibitor). The continuous dosing of 50 mg/l sodium nitrate together with 4 mg/l AQ would be effective in reducing the average aqueous H2S levels (40 mg/l) by at least 92%. This treatment would also be compatible with aeration or oxidation procedures to further increase the removal of H2S to achieve an aqueous H2S level of <1 mg/l. Aeration or oxidation would also increase the dissolved oxygen and COD levels, increase the inhibition of SRB activity and oxidise any reduced sulphur. The dosing of sodium nitrate and AQ to control the generation of H2S is not patented in South Africa. It can, therefore, be used to treat the Kraft mill effluent without violating any intellectual property rights in South Africa. / Dissertation (MSc(Applied Science))--University of Pretoria, 2008. / Chemical Engineering / unrestricted

Certaines études ont montré que des odeurs subliminales – odeurs d'intensité très faible activant le système olfactif mais non perçues consciemment – peuvent impacter le comportement alimentaire. Cependant, les mécanismes sensoriels et cognitifs impliqués dans le traitement des odeurs subliminales demeurent mal connus. Ce travail de thèse avait pour but d'explorer les activations cérébrales induites par des odeurs subliminales au moyen de l'Imagerie par Résonance Magnétique fonctionnelle. Durant les acquisitions IRM, les participants sont exposés à leur insu à deux odeurs présentées à intensité subliminale puis supraliminale. Quatre réseaux cérébraux mis en évidence par Analyse en Composantes Indépendantes s’avèrent spécifiques de la condition subliminale. Ces réseaux ne sont pas propres au traitement des odeurs et semblent liés à des processus attentionnels et de contrôle exécutif. La modulation de leur activité par des odeurs subliminales apporte des éléments nouveaux pour comprendre l’impact de ces odeurs sur le comportement, et suggère des applications possibles d'utilisation de ces odeurs pour réguler le comportement alimentaire. / Some studies showed that subliminal odours – odours of very low intensity which activate the olfactory system but are not consciously perceived – can impact food behaviours. However, the sensory and cognitive mechanisms involved in subliminal odours processing remain poorly known. This work aims exploring cerebral activity induced by subliminal odours by the means of functional Magnetic Resonance Imaging. During MRI acquisitions, participants were unknowingly exposed to two odours presented at subliminal intensity and then at supraliminal intensity. Four cerebral networks highlighted by Independent Component Analysis (ICA) prove to be specific to the subliminal condition. These networks are not particular to olfactory processing and seem to be linked to attentional and executive control processes. The modulation of their activity by subliminal odours brings new elements to understand the impact of these odours on behaviour, and suggests possible applications for using these odours to regulate food behaviour.

This thesis addresses key issues of scientific realism in the philosophy of biology and chemistry through investigation of an underexplored research domain: olfaction theory, or the science of smell. It also provides the first systematic overview of the development of olfactory practices and research into the molecular basis of odours across the 19th and 20th century. Historical and contemporary explanations and modelling techniques for understanding the material basis of odours are analysed with a specific focus on the entrenchment of technological process, research tradition and the definitions of materiality for understanding scientific advancement. The thesis seeks to make sense of the explanatory and problem solving strategies, different ways of reasoning and the construction of facts by drawing attention to the role and application of scientific representations in olfactory practices. Scientific representations such as models, classifications, maps, diagrams, lists etc. serve a variety of purposes that range from the stipulation of relevant properties and correlations of the research materials and the systematic formation of research questions, to the design of experiments that explore or test particular hypotheses. By examining a variety of modelling strategies in olfactory research, I elaborate on how I understand the relation between representations and the world and why this relation requires a pluralist perspective on scientific models, methods and practices. Through this work I will show how a plurality of representations does not pose a problem for realism about scientific entities and their theoretical contexts but, on the contrary, that this plurality serves as the most reliable grounding for a realistic interpretation of scientific representations of the world and the entities it contains. The thesis concludes that scientific judgement has to be understood through its disciplinary trajectory, and that scientific pluralism is a direct consequence of the historicity of scientific development.