A study of the monthly incidence and intensity of infection of Apodemus sylvaticus and Clethrionomys glareolus with selected intestinal helminths has been made. The majority of the variation in these two factors was shown to he due to differences in the age and sex ratio of the host populations throughout the year. Multiple regression and correlation analyses were used to assess the effect of independent environmental variables on the incidence and intensity of infection. A competitive interaction was found to occur between the trichostrongylid nematode Nematospiroides dubius and the oxyurid Syphacia stroma in the small intestine of Apodemus sylvaticus, though such an interaction did not lead to the total exclusion of either species. The distribution of N. dubius in the small intestine of laboratory mice was found to Be highly aggregated with respect to Both the intestine and the worm population; this was thought to occur in response to a gradient in oxygen tension along the mouse gut. Growth curves of male and female N. dubius in male and female mice were typically sigmoid and the daily growth rates for each sex of worm were the same in Both sexes of mice. The growth of the free-living stages was negative after infectivity had been reached. The respiration rates of male and female N. dubius increased with age, whereas those of the free-living stages decreased after infectivity was reached. The size/metabolism relationship for free-living stages N. dubius indicated a slow-down in metabolism as soon as infectivity was reached; this is likely to be of adaptive significance to a non-feeding stage. The size/metabolism relationship of both male and female parasitic stages indicated that aerobic metabolism may be important in vivo.

I conducted a series of research programmes on various aspects of Tardigrada biology. The published results of which are hereby presented as part fulfilment of my submission for a PhD by publications at Plymouth University. In this thesis my research publications are grouped into four chapters: Ecology & Faunistics, Alpha Taxonomy, Freshwater Fauna – a taxonomic challenge, and Superfamilies. In the first, I highlight my early papers which dealt with the faunistic surveys as I trained in systematics and taxonomy of the phylum. Amongst the key findings reported were the protozoan symphoriant, Pyxidium tardigradum van der Land, 1966, Marley and Wright (1994); a new addition to the reported fauna of the United Kingdom, Greaves & Marley(1996); and my first work on international samples from Arctic Canada, Sutcliffe et al.(2000). In the second chapter, Alpha Taxonomy, I have included five papers. The first, Marley and Wright (1996), illustrates my work with one of the Royal Museums of Scotland’s collections, where I updated the diagnoses of their specimens and described a new addition to the Icelandic fauna. The second paper, Russell, Marley & Hockings (2001), demonstrates how I was searching for new research methods to apply to tardigrades. It was because of similar exploration, with methods of SEM preparation, that I was invited to join the Australian-Anglo team working on sediment core samples from Antarctic freshwater lakes, Gibson et al. 2009. The remaining two papers in the chapter describe species new to science, Echiniscus ollantaytamboensis Nickel, Miller and Marley, 2001, and my first sole authored paper describing a species new to science, Platicrista ramsayi Marley, 2006. The third chapter, Freshwater Fauna – a taxonomic challenge, deals with a programme of research based initially on my findings at the Royal Museums of Scotland, Edinburgh. This then required subsequent visits the USA and Italy to work on the taxonomic issues with original authors on their more recently described genera. I prepared the original Case for the ICZN, but this was then held by the commission for several years pending their amendments to the Code. I then rewrote the Case into the final paper, Marley, Bertolani & Nelson (2008). The final chapter consists of two papers in which I worked on combining my expertise on the morphological characters of the buccal apparatus and claws, and combining this with new molecular dataset derived from sequencing individual specimens. My colleagues on these papers were Dr S.J. McInnes and Mr C.J. Sands, both from the British Antarctic Survey. Overall I am including 14 published papers and 5 published conference abstracts and three online articles. The following taxa were erected during this work: Pseudobiotus kathmanae, Echiniscus ollantaytamboensis, Platicrista ramsayi, Ramazzottidae, Isohypsibiidae, Macrobiotoidea, Eohypsibioidea, Hypsibioidea, and Isohypsibioidea. Plus the following taxa were re-described, Pseudobiotus, Thulinius, Thulinius augusti, Thulinius ruffoi, and Thulinius stephanae.

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No description available.

Wild animals are adapted to survive in different niches and therefore represent a great source for natural variation studies. Mapping of complex traits in model organisms has, for some time been constrained by low genetic variation of laboratory cultured strains. Although informative, this approach is fairly limiting. Recently, research in many model species has benefited from the creation of multi-parental crosses derived from wild-caught strains. Studying natural genetic variation using this approach allows for a better understanding of gene function as allelic interactions in divergent genetic backgrounds play important roles in determining complex traits. Such an approach was notably missing in Caenorhabditis elegans research. To remedy this, a new 4-parental recombination inbred line (RIL) panel that is representative of genotypically distinct groups of C. elegans isolates and distinct from the canonical N2 strain has been created. In this thesis I have used C. elegans, that has a short lifespan, high fecundity and wide array of genetic and genomic resources, to investigate variation in lifespan, its related traits and in the response to dietary restriction (DR). My specific aims were to further characterise a number of previously isolated lifespan QTLs, and to analyse lifespan and stress resistance in a new panel of 4-parent RILs. This work has discovered that the effect of DR on lifespan in C. elegans varies between genotypes and that such differences are seen in introgression lines (ILs), RILs and in wild isolates. A wide review of the literature on DR shows support for the view that genotype-specific effects on lifespan are widespread and that for some genotypes DR can be deleterious. I have also discovered that the newly created 4- parental panel of RILs contains significant, ecologically relevant, variation in lifespan and in stress resistance, that lifespan and stress resistance; are not correlated in these lines, and that this can be used to identify quantitative trait loci (QTLs) controlling this variation. Importantly, some of these QTLs cannot be explained by known lifespan regulating genes. Furthermore, the analyses revealed that the cold stress resistance in C. elegans is related to the control of translation, that the major QTLs detected in the RILs cannot be a consequence of genes known to be involved in cold stress resistance and that one may be a consequence of variation in eftu- 2 a part of the translation machinery. These results highlight the importance of exploring various genetic backgrounds in quantitative genetics and present a wider picture of the genetic interactions that are likely to be happening in the wild.

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No description available.

No description available.

The decrease in wild fish stocks has led to a search for novel feed sources to supply the aquaculture industry. Polychaetes have recently been identified as suitable feed ingredients due to their favourable nutritional composition, especially their lipid profile which is high in unsaturated fatty acids. As ragworm farms have started to develop, there has been a need to understand and improve rearing techniques, in particular the dietary requirements and nutritional profile of the ragworm. In this thesis, research was focused on the king ragworm. Nereis virens. The protein and energy requirements were identified by increasing inclusion levels of nutrients in the diet as well as manipulating feed rations from starvation to satiation. Weight gain, survival, ingested feed as well as protein and energy retention efficiencies were evaluated. Results demonstrated that N. virens gained a proportional amount of nutrient in relation to the amount ingested up to a critical amount when gain either stagnated or decreased. A pattern of nutrient retention and maintenance requirements for different weight classes were calculated. This data was then used for bioenergetic modelling to calculate nutrient requirements using the equation: Requirement: a x BW (g) + c x growth The energy maintenance requirement was found to be 18 J g-1 worm day-1; for protein, the requirement was 0.19 mg g-1 worm day-1. The predicted weight gain (g) for a worm of any given size (g) was y = 0.015g1.106. The total nutrient requirement is the sum of maintenance and growth, including the constant c which is the cost of nutrient deposition. Alternative feed sources were also investigated to observe the extent at which N. virens can utilize novel sources and their abilities to preserve or convert highly unsaturated fatty acids such as EPA and DHA. Results showed a high adaptability to terrestrial animal or vegetable based feed sources but an inability to convert shorter chain or n-6 fatty acids when fed non-marine based feeds. There may however be potential for N. virens to utilize other feed sources from its natural environment to supplement n-3 HUFA content.

Maternal effects are ubiquitous in free-living organisms, with parent-environment interactions affecting offspring life-history traits and fitness. These effects have been demonstrated in a wide variety of organisms, including mammals, insects and plants. Despite this, there is little evidence of maternal effects existing in parasites. If maternal effects are so prevalent in free-living organisms then it is unlikely that they do not exist in parasites. Maternal effects are important because they influence progeny fitness, measured by fecundity, longevity and developmental time. If they exist in parasite then they likely result in increased virulence, greater persistence (especially in terms of soil dwelling nematodes) and may be a driving influence in selection for resistance. Here, maternal effects are demonstrated in the free-living nematode Caenorhabditis elegans and the maternal effect of temperature demonstrated under constant and variable conditions. Similarly, the fitness effects of environmental temperature are explored in entomopathogenic nematodes and the effects of both maternal temperature and host species are demonstrated to cause changes in offspring development. Finally, C. elegans is used to demonstrate the importance of maternal effects in parasite life history and their potential impact on parasite control. The implications of altered life-history strategies that come about as a result of mothers tailoring their reproductive strategies in response to environmental cues for agricultural and medical parasite control are discussed. Critically, the effects of low parental exposure to anthelmintic compounds and nematicidal plant extracts on the fitness of offspring are demonstrated. This work provides evidence for the existence of maternal effects in freeliving and parasitic species and highlights the importance of the recognition of such effects in multiple fields.