The use of reproductive chemical cues is widespread amongst fishes. However, the most understood sex pheromone systems derive from species that employ a scramble spawning reproductive strategy. This thesis investigated for the first time the use of reproductive chemical communication in topmouth gudgeon <italic> Pseudorasbora parva</italic> (Temminck &amp; Schlegel) and sunbleak <italic> Leucaspius delineates</italic> (Heckel) that use two different forms of a male nest guarding reproductive strategy. In topmouth gudgeon, approximately a third of reproductive females adopted a body posture in response to reproductive male conditioned water advertising high receptivity to potential mates. Electro-Olfactory Gram recordings of reproductive male and female topmouth gudgeon revealed a high magnitude response to reproductive male and female odours. In addition, both topmouth gudgeon and sunbleak reproductive females responded to chemicals cues derived from conspecific reproductive males by an increase in swimming behaviour. In contrast to male topmouth gudgeon, reproductive male sunbleak responded to chemical cues from reproductive conspecific males and females. Active compounds were isolated from reproductive male topmouth gudgeon conditioned water by two different methods solid phase extraction (C-18 cartridges) and using a freeze drier. The eluate was subsequently separated using High Performance Liquid Chromatography into retention time fractions. An active fraction was identified using a bioassay guided separation. Nuclear Magnetic Resonance analysis showed that compounds were present in the active fraction. Chemical interaction between topmouth gudgeon (invasive to Europe) and sunbleak (native to Europe) was also investigated. Behaviour responses in the two species were asymmetrical topmouth gudgeon did not respond to sunbleak chemical cues. In contrast, both reproductive female and male sunbleak responded to topmouth gudgeon chemical cues. The results show that reproductive chemical communication is in operation in both test species. The cross species interaction indicates that pheromone pollution may represent an additional impact of non-native species introductions.

The pecking response of the Lesser Black-backed Gull (Larus fuscus) was investigated. This is a type of innate begging behaviour, whereby chicks peck at the red spot on the parent's bill to induce regurgitation of food. The pecking response in naive chicks was found to be released by a diverse range of stimuli, indicating an initial flexibility in this behaviour. However, chicks' reactions were swiftly adjusted with experience, which may be adaptive in rapidly learning the distinguishing features of their parents and the natal environment, as well as a variety of food items, such that chicks can feed effectively when in competition with siblings. Pecking behaviour was robust to predetermined variation between chicks, mediated by differences in egg and parental quality. Experiments were also conducted on the supernormal pecking response, which involves chicks pecking at a higher rate towards a long, thin, red rod with three terminal white stripes than they do towards the parental bill. Tinbergen and Perdeck (1950), who discovered this phenomenon, suggested that it was an adaptation to the angle at which a newly hatched chick crouching in the nest would first see the parental bill. This was addressed experimentally, along with the hypothesis that supernormal behaviour reflects chicks' innate feeding preferences. Little support was found for Tinbergen and Perdeck's (1950) hypothesis. There was some evidence that supernormal pecking is an adaptation to innate feeding preferences, with chicks choosing food items that shared properties with the supernormal stimulus (the white stripes, the red colour and the thinness). However, experimental evidence could not completely refute an alternative interpretation of supernormal behaviour as a non-adaptive byproduct of the chicks' nervous system (Ramachandran, 2004).

The developmental stress hypothesis proposes that complex songs evolved as honest signals of developmental history. I tested the mate choice behaviour of female zebra finches, Taeniopygia guttata, that had been reared under control conditions or nutritional stress. In a visual mate choice experiment, neither control nor stressed females showed agreement in preference but stressed females were less active than controls, and moved less often between stimulus males. In an acoustic choice experiment, females preferred complex songs to simplified ones, but stressed and control females did not differ in the direction or strength of song preferences. These findings suggest that quality of the rearing environment does not affect females' ability to discriminate between male signals, but could have long term, context-dependent effects on choosiness or other aspects of female choice behaviour. In contrast to previous studies, I found no difference between stressed and control males in brain or song characteristics. I calculated the relative influence of environmental and genetic factors on neutral development and song structure, finding evidence that song might signal information regarding both developmental history and genetic quality. I recorded male songs from wild zebra finches in a breeding colony in New South Wales. Song structure in this population predicted a male's reproductive success but not his morphology, or that of his mate. Finally, I summarize the evidence for the developmental stress hypothesis and suggest areas for further research. Together, my results illustrate the importance of understanding the consequences of early environmental conditions for female choice and male attractiveness.

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In the present thesis, we apply computational methods to the study of animal behaviour. Specifically, we are interested in the gradient navigation strategies of C. elegans, for which we show that there are many interesting questions that have not yet been answered by existing research. In order to study the behaviour of C. elegans, we first develop a range of tools to help us do so. We base a large part of our work on Markov-like models of behaviour and since these are not Markovian in the strict sense (limiting the analytical tools which can be used to study their behaviour), we first present a possible transformation from a Markov-like model with variable transition probabilities into a strictly Markovian model. We next present a framework for studying the behaviour of behavioural models which is not restricted to the work presented here but is likely to find general use in behavioural studies. Using these tools, we then analyse the chemotactic behaviour of C. elegans, showing that we can adequately explain most features of this behaviour using energy-efficiency considerations. We also show that the main behavioural strategy, so-called pirouettes is likely to be caused by an inability to sample the environment during a turn and that the animal my not be acting upon gradient information while reversing. Finally, we investigate the deterministic isotherm tracking strategy displayed by C. elegans. We develop a computational model for this behaviour which is able to reproduce all of the main features of C. elegans isotherm tracking and we propose a candidate neural circuit which might encode this strategy. Additionally, we briefly discuss the use of stochastic strategies by the animal when moving towards its preferred temperature. In summary, the work presented here therefore provides contributions to two major fields: we extend the methodology available for behavioural analysis in ethology and we contribute a number of insights and advancements to the field of C. elegans research.

Research funded by a PhD studentship from the Fisheries Society of the British Isles and UK Natural Environment Research Council grant-in-aid funding to Professor D. Sims

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No description available.

Traditional models of sexual selection based on the handicap principle assume a direct linkage between the degree of sexual signal exaggeration and the bearer’s quality, and set out a rather inflexible scenario where handicap exaggeration is maximised for sexual signalling purposes until it reaches the limit imposed by viability selection. Such a scenario makes it difficult to imagine the mechanisms by which multicomponent signalling systems can evolve and persist in time, given the costs of producing, disseminating and receiving signals. Based on non-equilibrium coevolutionary models, it has been suggested that variation in selection pressures derived from fluctuations in ecological and/or social conditions may lead to the emergence and maintenance of redundant and non-redundant multiple signals. Alternatively, the non-equilibrium dynamics to which coevolutionary systems are often subject can maintain multiple signals without environmental variability. Species with severe fitness constraints on costlier signal expression should be selected to utilize “cheaper” signals. And individuals not displaying at the maximum possible level might be selected to “compensate” their lack of fitness using phenotypically plastic traits, like behavioural ones. Here I investigate the effect of several potentially sexually selected barn swallow ornamental traits on several reproductive success indicators and on the habitat quality of foraging areas around breeding sites, and of several quality-indicating guppy traits on predator inspection activity, a behavioural character involved in mate choice. The findings presented here indicate ventral and throat plumage colouration, previously not studied for European barn swallows, to function as quality indicators and predict reproductive success and assortative mating patterns. Additionally, we found evidence for a “compensation mechanism” in both species studied, for individuals investing in “cheaper” sexual signals or not displaying at the maximum possible level.

Sexual selection is generally accepted as being responsible for the rapid and divergent evolution of male genitalia and other primary reproductive characteristics in internal fertilisers, such as testes size and sperm length. Selection can act via three main processes: sperm competition, cryptic female choice and sexual conflict, however very few studies have directly addressed the patterns of selection, the degree of phenotypic and genotypic variability expected in genital morphology or the degree to which intromittent genitalia are dependent on male condition. The seedbug, Lygaeus equestris has greatly elongated intromittent genitalia, being almost as long the body. Here I determine whether this is a sexually selected trait and further assess the degree of genetic and phenotypic variability in the greatly elongated male intromittent organ in relation to other morphological components. Further to this, patterns of inheritance and allometry of such exaggerated genitalia were investigated, and of the degree of condition dependence of genital and general morphology was experimentally assessed by varying food availability during ontogeny. Finally, using experimental evolution, I manipulated the level of sexual selection by biasing adult sex-ratio (male-biased, equal-sex, female biased) and investigated potential correlated evolution of female reproductive morphology and fertile (eupyrene) and non-fertile (apyrene) sperm length and numbers in the Indian meal moth, Plodia interpunctella. The main findings indicated that genital length was sexually selected in L. equestris being negatively related to male fertilisation success and that there was great phenotypic variation in genitalia both across and within populations. Genital length was negatively allometric, in spite of being hugely elongated, and was significantly heritable with considerable evolvability. It was also evident that there was genetic variation in the condition dependence of genital length with a significant genotype-by-condition interaction and much reduced genetic variation in genital length in the poor food treatment. Male and female primary sexual traits of P. interpunctella were also shown to covary, but this pattern did not differ across treatments. Taken together, the results presented in this thesis do not support traditional hypotheses of genital evolution and instead suggests that male intromittent genital length of L. equestris is sexually selected in a similar way to secondary sexual characteristics. This is also true when examining primary sexual traits in P. interpunctella and further highlights the false dichotomy between primary and secondary sexual traits.