Chemoreception plays an important role in predator-prey interactions and feeding dynamics. While the chemoreception of attractant or pleasant tasting compounds has been well studied, aversive chemoreceptive signaling has been difficult to investigate behaviorally in an ecological context because these interactions are species- and context- specific and deterrent compounds vary among prey. Using the coral reef system, this thesis explores on a molecular level the deterrent mechanism underlying detection by fish predators of an aversive compound, in order to gain a greater understanding of predator-prey interactions in this community. Like other organisms that are sessile or slow-moving, marine sponges have special mechanisms for defense from predation, commonly containing aversive-tasting compounds that defend these organisms from predation. To this end, we sought to identify and characterize a fish chemoreceptor that detects one or more of these compounds. We isolated a single cDNA clone encoding RAMP-like triterpene glycoside receptor (RL-TGR), a novel co-receptor involved in the signaling of triterpene glycosides. This co-receptor appears to be structurally and functionally related to receptor activity-modifying proteins (RAMPs), a family of co-receptors that physically associate with and modify the activity of G protein-coupled receptors (GPCRs). Expression in Xenopus oocytes showed that it responds to triterpene glycosides in a receptor-mediated manner and requires co-expression of a GPCR to enable signaling in oocytes; both of these receptors may be components of a larger signaling complex. A 40 bp portion of the gene is conserved across multiple fish species, but is not found in any other organism with a sequenced genome, suggesting that the expression of this receptor is limited to fish species. RL-TGR is the first identified gene encoding a co-receptor that responds to a chemical defense. This finding may lead the way for the identification of many other receptors that mediate chemical defense signaling in both marine and terrestrial environments, as this protein has the potential to represent the first of an entire family of co-receptors that respond to aversive compounds.

Erratum pages inserted onto front end papers. / Bibliography: leaves 226-244. / vi, 244 leaves ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis developed mathematical models of commercially exploited fish populations, addressing the question of how to harvest a predator-prey metapopulation. Optimal harvesting strategies are found using dynamic programming and Lagrange multipliers. Rules about harvesting source/sink populations, more/less vulnerable prey subpopulations and more/less efficient predator subpopulations are explored. Strategies for harvesting critical prey subpopulations are suggested. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied Mathematics, 2000?

Diving vertebrates are constrained by an aquatic existence because they carry a limited store of oxygen whilst submerged and must return to the surface to breathe. Therefore, oxygen stores must be used efficiently in order to maximise aerobic dive duration. The ability to use additional, non-pulmonary gas exchange to obtain oxygen from the water provides a mechanism to alleviate the use of body oxygen stores and extend dive duration. The partitioning of gas exchange between aerial and aquatic modes is predicted by the theory of optimal breathing. As the cost of obtaining oxygen by one mode increases, the reliance on this mode should decrease whilst the reliance on the alternate mode should increase. A number of environmental, physiological and ecological factors can affect metabolic rate and/or the partitioning of gas exchange between aerial and aquatic modes, with consequences for dive duration. The overall aim of this study was to examine the effects of temperature, specific dynamic action and predation on respiratory partitioning and diving behaviour in the Arafura filesnake, Acrochordus arafurae. Filesnakes provide an excellent model to address the aims of this study because they are fully-aquatic and respire bimodally, utilising both aerial and aquatic (cutaneous) gas exchange. Metabolic rate and diving behaviour are usually thermally dependent in diving ectotherms. Given this knowledge, we tested whether A. arafurae was capable of up-regulating cutaneous oxygen uptake to compensate for the temperature induced increases in metabolic rate. Metabolic rate had a Q10(20-32°C) of 2.33, however cutaneous oxygen uptake was independent of temperature and all elevated metabolic demands were met by increasing aerial oxygen uptake. Consequently, maximum dive duration was reduced by 70%, from 77 min at 20°C to 28 min at 32°C. The temperature independence of cutaneous oxygen uptake suggests that blood PO2 remained stable across temperatures and the increased blood flow expected with an elevated metabolic rate did not enhance the capacity for oxygen uptake (diffusion limited rather than perfusion limited). Although cutaneous oxygen uptake was not regulated, its contribution to extending dive duration was significant. When the ability to respire aquatically was removed (severe hypoxia), dive duration was reduced by up to 30%. Acrochordus arafurae feeds infrequently on large, high-protein meals thus the postprandial metabolic response was significant. Meal size and fast length (13 days or one month) were both positively related to the peak metabolic scope. After fasting for one month, peak rate of oxygen consumption was up to 12-fold standard metabolic rate (SMR) with the largest meal size. By comparison, an animal that was fasted for 13 days and fed an equivalent meal size incurred a six-fold increase in SMR. The energetic costs of digestion (specific dynamic action, SDA) increased with meal size, but fast length had no effect, suggesting the up-regulation of gut function was not a significant cost in the SDA. Pulmonary and cutaneous gas exchange increased with elevated metabolic demands however pulmonary oxygen uptake was the dominant mode. Despite the increase in cutaneous oxygen uptake during digestion, maximum dive duration decreased by between 50% and 90% of fasted values. The significant reductions in dive duration following feeding may have implications for predator vulnerability. Diving animals are most vulnerable to predation at the water’s surface. The theory of optimal diving under predation predicts that animals should make shorter, more frequent surface intervals or longer, less frequent surfacing intervals to minimise exposure to predators. Acrochordus arafurae is prone to aerial (birds of prey) and aquatic (crocodiles, large fish) predation. Simulated avian predation did not change dive or surface duration or proportion of time at the surface or spent active. However, a greater number of longer dives were observed with fewer long surface intervals suggesting an increase in the use of cutaneous oxygen uptake. The nocturnal diving patterns of A. arafurae provide an in-built anti-predator strategy. The threat of aquatic predation by a large fish produced atypical anti-predator responses; A. arafurae became increasingly active, reduced dive duration and increased surface interval which was indicative of a foraging response. The field diving behaviour of adult A. arafurae was determined using acoustic telemetry and interpreted in the context of environmental and ecological conditions. The mean dive duration was 6.6 min, with 85% of dives less than 10 min in duration. The maximum dive duration was 153 min. There was no diel pattern in dive duration. Snakes were located at an mean depth of 0.62 m, however, they occasionally ventured to greater depths (up to 6 m) but very infrequently. Snake body temperature reflected water temperature and fluctuated by approximately 1°C on a daily basis. The short and shallow dives of A. arafurae minimise travel costs associated with surfacing and may be an anti-predator strategy. Metabolic rate and respiratory partitioning is dependent on physiological and ecological factors with consequences for dive duration. Temperature and postprandial induced increases in metabolic demands were met by increasing the reliance on aerial gas exchange given the limitations of cutaneous gas exchange; and dive duration was substantially reduced as a result. Ecological factors, such as predation, can increase the cost of surfacing and promote the use of aquatic gas exchange. However, changes to behaviour, including habitat choice, residence depth and the employment of a diving strategy that does not maximise dive duration may be just as effective at minimising the costs and maximising the gains of a dive.

I studied aspects of the ecology of the Murray River turtle, Emydura macquarii, to determine the impact of the introduced red fox, Vulpes vulpes. The fox is one of Australia's worst vertebrate pests through its predation on livestock and native mammals, but their impact on reptilian communities is not known. I conducted a large-scale mark-recapture study to evaluate population growth of E. macquarii in the Albury region of the upper Murray River by determining growth, reproduction and survival. The study was conducted downstream of the first, and largest, impoundment on the Murray River, Lake Hume. Emydura macquarii predominantly inhabit the lagoons in the upper Murray River, as the mainstream and Lake are possibly too cool to maintain metabolic processes. They are easily captured in hoop traps and the use of live decoys maximises trap success. Over 2000 hatchling turtles were marked and released into two lagoons between January 1997 and January 1998. Growth of these individuals is rapid over the first few years but declines towards maturity, and is indeterminate after maturity. Although growth annuli are not well defined, even on young individuals, the von Bertalanffy model describes the growth of both male and female E. macquarii. Male turtles mature at 5-6 years and females mature at 10-12 years. Female turtles may maximise reproductive potential by delaying maturity and producing one relatively large clutch (mean = 21 eggs) per year, which is positively correlated with body size (PL). Although primarily related to body size, clutch size varies annually because of environmental conditions. If winter and summer rainfalls are below average and temperatures are above average, E. macquarii may reduce clutch size to increase the chance of the eggs surviving. Nesting predominantly occurs during the first major rain-bearing depression in November. Habitat variables, including distance from water, nearest nest, and tree, and soil type were measured for each nest to determine characteristics that attract predators. Nests close to the shoreline and trees are heavily preyed on, and nests constructed in sand are less likely to be destroyed by predators. Foxes detect nests through a combination of chemical cues from eggs and slight soil disturbances, whereas birds only destroy nests observed being constructed during the day. Female turtles alter nesting behaviour and construct nests much further away from water when foxes were removed and as a result, nests are less dense and away from trees. Thus in high predation risk areas, turtles minimise emergence and search times to reduce the risk of direct predation by foxes. Predation is reduced when nests are in lower densities and away from trees, because predators increase search efforts when nests are in higher densities and birds are more likely to destroy nests close to trees. Reproductive success is further reduced in high predation risk areas because more nests are constructed in sandy substrates where clutch success is reduced compared to incubation in more dense substrates. Where predators are a significant source of mortality, prey may use indirect methods, such as chemical recognition, to avoid encounters. Nesting turtles did not avoid areas where fox odour was present, suggesting that they assess predation pressure from foxes by other mechanisms, such as visual recognition. However, an innate response occurs to the odour of a once common predator on the Murray River, the eastern quoll (Dasyurus viverrinus), whereby turtles recognise and avoid nesting in areas where quoll odour is present. Therefore nesting turtles show a similar avoidance response to two different predators, using different mechanisms of detection. Similarly, predation risk may influence hatching times and nest emergence. The rate of embryonic development of E. macquarii may increase or eggs may hatch early so that the clutch hatches synchronously, thereby reducing the risk of predation through group emergence from the nest. Emydura macquarii reach densities of over 100 turtles.ha-1, with the majority of the population consisting of sexually mature individuals. Emydura macquarii has a Type III survival curve where mortality is extremely high in the egg stage (93% nest predation), remaining high over the hatchling stage (minimum survival rate- 10%), but decreasing rapidly throughout the juvenile stage (~70% juvenile survival). Adult survival is extremely high, with greater than 95% of adults surviving each year. Foxes through nest predation cause most mortality but a small proportion (~3%) of nesting adult females are killed by foxes each year. A removal program evaluated the impact of foxes. In 1996, fox numbers were monitored around four lagoons by spotlighting and non-toxic bait uptake. Foxes were removed from around two of the lagoons throughout 1997 and 1998, using spotlight shooting and 1080 bait poisoning. Fox numbers were continually monitored around all four lagoons during the study. Nest predation rates remained around 90% in all sites where foxes were present, but fell to less than 50% when foxes were removed. At the same time, predation on nesting female turtles was eliminated where foxes were removed. Demographic models using staged based survival schedules, together with growth and fecundity values for E. macquarii show a decline of 4% per year in these populations. Elasticity analyses shows that survival of adult female E. macquarii has the major influence on population stability and a reduction of nest predation alone is unlikely to address the population decline. Management options, such as reducing foxes prior to nesting around key lagoons, will stabilise the population decline, and eliminating foxes completely from certain areas with high dispersal potential, will promote recruitment of juvenile E. macquarii.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1994. / Document électronique également accessible en format PDF. CaQCU

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 53-58). Also available on the World Wide Web.

Ce travail de thèse est une exploration ethnologique des propriétés générales et des vérités fondamentales que les Indiens Wayana de Guyane française (Amazonie), de langue karib, reconnaissent aux animaux, entre autres non-humains, ainsi qu’une étude des différentes formes de relations entre les humains et ces non-humains, en particulier la relation de prédation, lorsque les uns tuent et mangent les autres. Ce travail expose tout d’abord les différents non-humains qui peuplent le monde wayana, dont l’animal est une des formes. Puis, à partir d’outils théoriques et par une étude lexicale, la thèse étudie la nomenclature et la classification des entités non-humaines du point de vue wayana. Face aux impasses révélées par cette approche, la thèse expose les propriétés ontologiques des entités non-humaines, pour reconnaître une conception animiste des non-humains. Ce modèle, anthropocentré, au perspectivisme absent, s’avère mettre l’accent sur une équivalence réelle des rapports au sein des différentes bulles d’existants. Par l’étude des différentes positions de consanguinité et d’affinité dans leurs interactions avec les non-humains, ce travail révèle que, dans la relation de prédation avec l’animal, cet autre est avant tout un affin potentiel. On noue avec lui une relation d'ennemi à ennemi qui fonctionne par soustraction et sans institution d’arbitrage. Par l’étude des techniques de prédation, la thèse démontre que les Wayana mettent en œuvre des moyens de prédation les plus efficaces possibles. Si les Wayana cherchent un rendement optimal, il ne s’agit pas de maximiser les gains, mais de minimiser les risques dans une relation de prédation avec un ennemi. / This thesis is an ethnographic exploration of the general properties and fundamental truths that Indians Wayanas of French Guiana (Amazon), karib, recognize to animals, among other non-human beings, and a study of different forms of relationships between humans and non-humans, in particular the relationship of predation, when the ones kill and eat the others. First of all, this work presents the various non-human inhabitants of the Wayana world, of which the animal is one of the forms. Then, from theoretical tools and a lexical study, the thesis examines the nomenclature and classification of non-human entities from Wayana perspective. With the impasse revealed by this approach, the thesis presents the ontological properties of non-human entities to recognize an animistic conception of non-humans. This model, anthropocentric, without perspectivism, appears to focus on a real equivalence on relationships inside each boxes of beings. By studying the different positions of consanguinity and affinity in their interactions with non-humans, this work shows that in the relationship of predation with the animal, the other is primarily a potential affine. Is tied with him, an enemy to enemy relationship, working by subtraction without arbitration institution. By studying the techniques of predation, the thesis demonstrates that Wayanas implement means of predation the most effective. If Wayana are seeking for optimum performance, it is not so much to maximize the gains, but is to minimize the risks in a relationship of predation with an enemy.

Orientador: Odair Aparecido Fernandes / Banca: Ivan Cruz / Banca: Antonio Carlos Busoli / Banca: Fernando Luís Cônsoli / Banca: Nelson Wanderley Perioto / Resumo: O presente trabalho objetivou avaliar a dinâmica populacional de S. frugiperda em ambientes de com alta e baixa diversidade vegetal no entorno da cultura do milho. Além disso, visou-se observar o comportamento e o processo de interação entre os inimigos naturais T. remus, T. pretiosum e D. luteipes. Em nenhuma das datas de avaliação estudadas detectou-se diferença significativa no número médio de adultos e posturas de S. frugiperda. Quanto ao número de lagartas/planta, as áreas de vegetação não diversificada apresentaram maiores valores. Os predadores apareceram em maior número geralmente após os 30 DAE e preferiram as áreas de vegetação não diversificada. Já os parasitóides concentraram-se na cultura até os 25 DAE e preferiram as áreas de vegetação diversificada. Quando foi avaliada a competição entre T. remus e T. pretiosum não constatou-se multiparasitismo. Entretanto, quando as fêmeas de T. remus e T. pretiosum foram colocadas juntas sobre a mesma postura, T. remus predominou. Já quando T. remus foi colocado com D. luteipes observou-se que quando as posturas de S. frugiperda foram expostas primariamente ao parasitóide, D. luteipes as consumiu, mas somente até o terceiro dia após o parasitismo. T. remus parasitou ovos de D. luteipes com até 48h de desenvolvimento embrionário, mas apenas quando as fêmeas do predador estavam ausentes. / Abstract: This work aimed at evaluating the population dynamics of S. frugiperda in maize culture with high and low vegetal diversity around. And objectified to observe the behavior and interaction between the natural enemies T. remus, T. pretiosum and D. luteipes. Was not detect significant difference in number of S. frugiperda adults and egg masses throughout the time and at the areas of diversified vegetation or not. No diversified areas presented a higher number of larvae/plant. The predators had appeared in higher number after 30 days plants emergence and generally they preferred the areas of no diversified vegetation. The parasitoids were concentrated in the culture until the 25 days after plants emergence and had preferred the areas of diversified vegetation. When S. frugiperda eggs were exposed to either parasitoid previously, there was no emergence of the other parasitoid. And, when the T. remus and T. pretiosum females were placed together with S. frugiperda eggs, it was observed a greater parasitism by T. remus. The results showed a lack of multiparasitism by both species. When S. frugiperda eggs were exposed to T. remus previously, D. luteipes eat the eggs until three days after parasitism. T. remus parasitized D. luteipes eggs until 48h they were laid, but only when predator females were absent. / Doutor