Most of the work on Protozoa has been confined to the laboratory. Apart from the aspects of economic importance, particularly medicine, the cytology, physiology and genetics of many groups have been comprehensively studied. With the introduction of the electron microscope there has been a spate of works on the ultra-structure of Protozoa (see Robertson 1958).

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Cercozoa: I) biodiversity, distribution, and ecology on a global scale, and 2) the internal phylogeny of the phylum and lower ranking taxonomic groups within it. Additionally, the relationship of Cercozoa to their closest relatives within the infrakingdom Rhizaria, Foramini fera and Radiozoa, were investigated by screening for the presence and nature of poly ubi quit in insertions (Chapter 11). Within Cercozoa and in addition to many 18S rDNA analyses, the utility of 28S rDNA sequences in cercozoan phylogenetic analyses was investigated, both as single gene analyses and when concatenated with 18S rDNA (Chapter 12). Environmental 18S rRNA gene libraries were created using phylum-specific primers from globally distributed sites and a wide range of ecological conditions. These were used to construct a new cercozoan phylogeny, and demonstrate that the number of lineages within Cercozoa is far greater than previously imagined, both within known groups and in the form of novel clades (Chapter 4). Phylum-wide patterns of geographical and ecological distribution were investigated. Some clades were only recovered from particular sampling sites, suggesting geographically and/or ecologically restricted distributions. This is a pattern seen in all environmental gene libraries analysed, but is often eroded by more intensive sampling. Further studies using molecular probes that specifically target some of these groups suggest that distribution patterns differ between lineages/clades. Statistical comparison of library compositions from New Zealand and Panama suggest that on a global scale, cercozoan communities are affected by ecological conditions, but not by geographical distance (Chapter 5). A review and meta-analysis was constructed of all publicly available environmentally-derived eukaryote sequences, showing that Rhizaria accounted for nearly 10% of all unique sequences detected and that cercozoan sequences have been recovered from all environments except pelagic and deep-sea samples (Chapter 3). New sequences were also obtained from pure cultures of diverse cercomonads (Chapter 8), heteromitids (Chapter 9), and proteomyxid and endomyxan amoebae (Chapter 10). These were combined in analyses with all available environmental sequences. The results of these studies are informative about the ecology and phylogeny of each (now known to be substantial) group, and demonstrate that many classification changes need to be made, some of which are proposed in this thesis. The very large number of cercomonad sequences generated has led to a comprehensive revision of tbe former genus Cercomonas. Many environmental 18S rDNA libraries specific to cercomonad subclades allow a comparison of distribution patterns at this fine phylogenetic scale with the broader phylum-wide surveys (Chapter 7). ITS rDNA sequences from two small cercomonad clades were used to map geographical and ecological distribution at an even higher level of phylogenetic resolution (Chapter 6)

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The obligate intracellular parasite Plasmodium falciparum causes the most severe forms of human malaria. Apical rhoptry organelles of invasive merozoites contain proteins that are instrumental to the intraerythrocytic development of the parasite. Our group has determined that the RhopHl protein of the high molecular mass rhoptry complex (RhopH) is encoded by genes of the highly-conserved clag (cytoadherence-linked asexual gene) family. In this study, the characterisation of the RhopH 1/Clag proteins is continued. It was ascertained that the family has five members in P. falciparum 3D7 (clag2, -3.1, -3.2, -£and -9), each of which is transcribed. Specific antibodies were raised to demonstrate that all Clags are expressed at the apical end of merozoites, but in an apparently differential distribution. Both Clag3.1 and Clag9 are found in the basal bulb of the rhoptries as part of the RhopH complex. However, Clag2, -3.2 and -8 appear to remain outside the complex and their distribution is distinctly more apical, potentially in the region of the rhoptry neck. It was determined that RhopH complexes contain only individual Clag members in a mutually exclusive association, thereby suggesting the existence of multiple complexes in which specificity is conferred by RhopH 1/Clag. Those Clag proteins that are part of the RhopH complex are carried into the newly invaded red blood cell where they persist. There is evidence to suggest that Clag3.1 and Clag9 are trafficked across the parasitophorous vacuolar membrane, and that their function is in the developing parasite. Clag9 is the most diverse member of the family and was originally proposed to be involved in the pathogenic process of cytoadhesion from the surface of the infected red blood cell. However, we have now identified it as a rhoptry protein. This may suggest that Clag9 is indirectly involved in cytoadherence within the cycle that follows erythrocyte invasion.

The main purpose of the work was to carry out a detailed seasonal study of the distribution and ecology of the living benthonic foraminiferids in the different environments around the Ebro delta. As a background to the ecological work, a rough sedimentologiacal examination of the Ebro delta itself was attempted. The delta is relatively small, having a surface area of 330 sq. km., and discharge from the River Ebro is sufficient only to keep one outlet open. Four maj or phases of delta gro1rth are recognized and some of these are known to have had more than one river outlet. The river has only recently changed to a mew direction of discharge and abandoned a section of its channel. Levee, abandoned channel, marsh; lacustrine, beach/spit, lagoon, delta front platform and pro delta slope sedimentary environments are distinguished and described; sediment accumulation is most rapid on the delta front platform and the pro delta slope directly off the river mouth. Seven living foraniferal assemblages are described and a method, involving the use of 'percentage similarity indices', is utilized for the detection of offshore faunal boundaries.