Thesis (Ph. D.)--Oregon State University, 2004. / Printout. Includes bibliographical references. Also available on the World Wide Web.

A population of three-spined stickleback, Gasterosteus aculeatus L., was sampled every two weeks for 14 months from Airthrey Loch on the campus of the University of Stirling. A total of 857 fish were collected and three species of parasites were studied. The monogenean Gyrodactylus gasterostei was found on the skin and fins and two myxosporean parasites, Sphaerospora elegans and Myxobilatus gasterostei, were present in the kidney. All parasite species were present throughout the year but abundance was correlated with the yearly life cycle of the host fish. Lower prevalence and intensity were observed in summer due to the large number of young fish in the samples. The comparative ultrastructure and development of the two myxosporeans was studied by light and transmission and scanning electron microscopy. Both myxosporeans followed the general pattern of myxosporean development but showed some novel features. Sphaerospora e/egans had two distinct developmental cycles. A proliferative cycle involving extrasporogonic stages occurred in the blood whereas spore production occurred in the kidney. Light microscopy of Giemsa stained blood smears suggested proliferation of extra-sporogonic stages by external budding or plasmotomy. Structural similarities between extra-sporogonic blood stages and sporogonic kidney stages are discussed. Although S. elegans mostly formed disporous plasmodia, monosporous plasmodia were also occasionally observed. Before the appearance of sporogonic cells within the early pseudoplasmodia, certain areas of pseudoplasmodial cytoplasm became electron lucent, eventually acquired cell organeUes and later appeared as sporogonic cells. Developing valvogenic cells contained protuberances at the posterolateral side of spores which disappeared in mature spores. Characteristic lipid bodies were seen in developing capsulogenic cells and developing uninucleated sporoplasmic cells contained abundant glycogen granules. The sporoplasmic cells were devoid of sporoplasmosomes. Plasmodia of M. gasterostei were mono, di or polysporous and showed features of both coelozoic and histozoic myxosporeans, including a unit surface membrane, simple pinocytosis aanand presence of a number of vegetative nuclei and generative cells, the latter which formed pansporoblasts before the initiation of sporogenesis. A membrane bound tubular structure and some electron dense fibrillar bundles are previously undiscovered cytoplasmic organelles of the plasmodia. Developing capsulogenic cells contained characteristic membrane bound vacuoles filled with electron dense (glycogen) material. Myxobilatus gasterostel attached to the epithelial cells by plasmodial surface projections and there were electron dense areas at the point of attachment. Sphaerospora elegans showed occasional hairlike processes projecting from the pseudoplasmodial surface to the microvillous brush border of the epithelial cells. There were no electron dense areas at the point of attachment to the epithelial cells of the kidney tubules. Early undifferentiated pre-sporogonic stages of both parasites were occasionally present intracellularly in the tubular epithelium suggesting this is a route of entry into the tubular lumen. Early stages of S. elegans were also seen in the capillary lumen of the glomerulus. Intracellular and intraluminal stages of S. elegans and M. gasterostel caused pathological changes in different ways. Histopathological changes associated with S. elegans included vacuolation and accumulation of electron dense material in the epithelium whereas M. gasterostei caused large vacuolation with necrosis of the epithelial layer. Both parasites caused destruction of glomerular tufts in heavy infections and an increased number of rodlet cells in the epithelial layer were common in both cases. The two myxosporean species were most abundant during the winter and spring. Extra-sporogonic stages of S. elegans were found only in January and June in the rete-mirabile of the eye, circulating blood and kidney. In infections with S. elegans sex of the host fish was apparently of no significance, whereas significantly lower infestations occurred in male sticklebacks infected with M. gasterostei compared with females. Host size was important in determining the prevalence and intensity of both myxosporean species. Older fish were less heavily infected, possibly due to an acquired immunity or pathogenic effects on the host. A high number of mixed infections indicated that there was no interspeciflc competition between the two parasites. There appeared to be a continuous recruitment of myxosporeans throughout the year. Studies on myxosporean spore shedding suggested that spore production and shedding was continuous throughout the year and was uninfluenced by temperature or season. Gyrodactylus gasterostel was generally more abundant in winter and spring than in summer and autumn, reflecting the greater numbers of small young of the year fish at these times. The age of the host fish was a significant factor influencing the prevalence and intensity of infestation with G. gasterostei. Sex of the host had no apparent influence on infestation. The parasite was highly overdispersed within the host population and its distribution was best fitted by the negative binomial.

Orientadores: Nelson da Silva Cordeiro, Sarah Arana / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-14T17:07:43Z (GMT). No. of bitstreams: 1 Barassa_Bianca_D.pdf: 5238777 bytes, checksum: 8c674b6d8dd51bbd55f95465206cedc7 (MD5) Previous issue date: 2009 / Resumo: A susceptibilidade à infecção natural por parasitos do filo Myxozoa foi avaliada em Salminus brasiliensis (dourado) e Leporinus obtusidens (piapara), oriundos de ambiente natural. Durante o período de 2005 a 2007, 60 dourados e 60 piaparas, foram colhidos no rio Mogi-Guaçu em trechos a jusante da barragem da Cachoeira de Emas, localizada no município de Pirassununga, SP, Brasil. (...continua) / Abstract: The susceptibility to natural by Myxozoan parasites was evaluted in Salminus brasiliensis (dourado) na Leporinus obtusidenss (piapara), from the natural environment. During the period of 2005 to 2007, 60 dourado and 60 piapara were collected in the river Mogi-Guaçu, near Cacheira de Emas, located in the municipality of Pirassununga, State of São Paulo, Brazil. (¿to be continued) / Doutorado / Doutor em Parasitologia

Orientador: Marlene Tiduko Ueta / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-20T22:39:13Z (GMT). No. of bitstreams: 1 Muller_MariaIsabel_D.pdf: 17246609 bytes, checksum: 3a8aafad3f2f9c39e25664a81ae6e807 (MD5) Previous issue date: 2012 / Resumo: O pacu Piaractus mesopotamicus (Holmberg, 1887) é uma das principais espécies de importância econômica no Brasil. Peixe nativo da Bacia dos rios Paraná e Paraguai é uma das espécies mais comuns em pisciculturas. Mixosporídeos e monogêneas são parasitos de alta prevalência e causam danos em cultivos comerciais, tornando importante seu estudo detalhado. Neste estudo foram examinados 278 especimens de P. mesopotamicus de vários tamanhos, no período de Fevereiro de 2008 a Julho de 2010, coletados nos tanques do Centro de Pesquisa e Conservação de Peixes Continentais - CEPTA/ Instituto Chico Mendes de Conservação da Biodiversidade - ICMBio, Pirassununga, SP e em pisciculturas particulares da mesma região. Os parasitos identificados foram os mixosporídeos Henneguya piaractus (Martins & Souza, 1997) e Myxobolus colossomatis (Molnár & Békési, 2007) e os monogêneas Anacanthorus penilabiatus (Boeger, Husak & Martins, 1995), Mymarothecium viatorum (Boeger, Piasecki & Sobecka, 2002) e Dactylogyridae sp1 (não identificada). Análises ultraestruturais mostraram em Henneguya piaractus uma fina camada granular entre o plasmódio e as células do hospedeiro, uma única parede no plasmódio com numerosos canais de pinocitose. Myxobolus colossomatis apresentou uma camada plasmodial com numerosa atividade fagocítica em comunicação com as células do hospedeiro. A histopatologia apresentou hiperplasia nas lamelas branquiais em peixes altamente infectados e deformação das lamelas em relação a cistos de H. piaractus. A microscopia eletrônica de varredura mostrou para A. penilabiatus tegumento relativamente liso e microvilosidades nas regiões adesivas. Mymarothecium viatorum apresentou na superfície de seu tegumento, projeções similares a escamas com variações tipo microvilosidades. Análises moleculares utilizando marcadores ribossomais para mixosporídeos e monogeneas (porção18S) posicionaram as espécies em árvores filogenéticas. A descrição do genoma mitocondrial parcial de A. penilabiatus é apresentada / Abstract: The freshwater fish Piaractus mesopotamicus (Holmberg, 1887), popularly known as "pacu", is one of the most economically important species of fish in Brazil. The fish is endemic to the Paraná-Paraguay river basin, and is one of the species that is most cultivated in fish farms. A detailed study of Myxosporea and Monogenea is important, due to their high prevalence and the damage they cause in commercial fish farms. A total of 278 specimens of P. mesopotamicus were examined from February 2008 to July 2010, collected in fish ponds at the Centro de Pesquisa e Conservação de Peixes Continentais (CEPTA), Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio), in the city of Pirassununga, in the state of Sao Paulo, and in other commercial fish farms nearby. The main parasites found were the myxosporeans Henneguya piaractus (Martins & Souza, 1997) and Myxobolus colossomatis (Molnár & Békési, 2007) and the monogeneans Anacanthorus penilabiatus (Boeger, Husak & Martins, 1995), Mymarothecium viatorum (Boeger, Piasecki & Sobecka, 2002) and Dactylogyridae sp1 (not identified). Ultrastructural analysis of H. piaractus showed a thin layer of granular material between the plasmodial wall and the host cells. The single plasmodial wall was connected to a plasmodial ectoplasm zone through numerous and extensive pinocytotic canals. Myxobolus colossomatis showed a plasmodial ectoplasm zone with numerous and extensive phagocytic activity, and numerous projections in the direction of the host cells. Histopathological data showed hyperplasia in the lamellae in highly infected fish and deformation of the lamellae regarding cysts of H. piaractus. Scanning electron microscopy found that A. penilabiatus had a relatively smooth tegument and microvilli in the adhesive regions. However, the M. viatorum tegument showed that the top surface had variations similar to scales. Molecular analysis, using ribosomal markers for myxosporeans and monogeneans (18S rDNA) positioned the species in phylogenetic trees. The partial mitochondrial genome of A. penilabiatus is also recorded / Doutorado / Parasitologia / Doutor em Parasitologia

Kudoid parasites are common in marine fish and their affects range from relatively benign to pathogenic. They are notorious in the seafood industry for spoiling fish meat, either by muscle liquefaction or by producing unsightly macroscopic cysts. Kudoids also infect several other tissues such as brain, heart, gills, connective tissue, intestinal smooth muscle, and epithelia. Since the revised classification of the Kudoidae in 2004, kudoid myxospores have a range of shapes, but with two main characteristics: they have four or more spore valves with the equivalent number of polar capsules. With relatively few morphological traits to base kudoid species descriptions, DNA has proven to be increasingly useful to specifically diagnose infections. However, to properly utilise genetic information, there is a need to understand how genetics relates to the biological characteristics of species. This will ensure the genetic markers used are appropriate for species characterisation. This project aimed to develop an understanding of how biological characteristics including morphology, tissue tropism, host specificity, and geographic distribution correlate with genetic relatedness of kudoid species, and how this information could be employed to facilitate diagnosis and characterisation of species. A taxonomic investigation of kudoid isolates, mostly from the east coast of Queensland, Australia, was conducted using information on host identity, locality, infection status, tissue of infection and histological response to infection. Together with spore morphology and DNA relationships, comparisons were made with existing data from literature. Forty-three small subunit and 68 large subunit ribosomal DNA sequences were generated from kudoid isolates for this project. The two gene regions showed similar relationships amongst the kudoids, however the genetic variability between closely related species was less conserved in the large subunit, and showed superior species resolution that correlated with subtle morphological differences of spores. Broadly speaking, genetic relatedness of kudoids is closest for species infecting the same type of tissue with similar spore morphology. Within these tissue/morphology groups, some relationships were emerging from genetic correlations with pathology, however there are weaknesses in utilising this characteristic since pathology may change with host species or host age. Similar relationships to pathology were seen from geographic locality; however, the limited number of areas that genetic data originates from may have introduced some bias. Lastly, there were very few genetic relationships that correlated with host relatedness. The taxonomic affinities of the new kudoid isolates lead to the characterisation of six novel kudoid species and four additional host-parasite combinations. The investigation into these new species highlighted the broad host ranges and geographic distribution of some kudoid species. Genetic mixing of kudoid species populations from the east coast of Queensland, Australia with Japan was noted. For example, Kudoa amamiensis was discovered from carangid and pomacentrid fish from Queensland, increasing the host range from eight (seven from Japan, one from north Queensland) to 11 host species. Also, geographic distribution was extended to Heron Island on the south Great Barrier Reef (Queensland). The distribution did not extend to rocky temperate reefs further south. Another example is Kudoa yasunagai which was previously recorded from four fish species in Japan and one from the Philippines. Now the distribution has been extended to North Stradbroke Island in Southern Queensland from three additional host species. The connection was made between these host isolates with the assistance of DNA and a novel way of analysing morphological data in species that have variable morphotypes i.e. different numbers of polar capsules in the spores. It was confirmed that the dominant morphotype can vary between different hosts and even host samples of the one species. Genetic data has also proven useful in the determination of host range. An analysis of kudoid host specificity showed just over two thirds of the described kudoid species have been recorded from a single host; the remainder have been recorded from two to 38 host species. By using DNA data, 17 new hosts were recorded for K. thalassomi (total 18 hosts). The new hosts came from six different host families, but these fish shared the same habitat on the Great Barrier Reef. Other high host range kudoid species may be disproportionately broad as similar morphological species may have been misidentified from some hosts. For example, the host range of K. thyrsites (38) is likely to represent a species complex that may be split pending further genetic analyses. From this study, it has been reinforced that a holistic approach to species definition is important. Genetic analysis has become a particularly valuable tool; however, in conjunction with biological data such as spore morphology, pathology, host range, and geographic distribution, our understanding of kudoid parasites becomes more robust and provides important knowledge for diagnostics and aquaculture management. In the future, significant improvements in kudoid understanding will coincide with the solving of kudoid life cycles and transmission patterns.

Orientador: Edson Aparecido Adriano / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-17T17:30:24Z (GMT). No. of bitstreams: 1 Milanin_Tiago_M.pdf: 1632570 bytes, checksum: 89ed3ce864242183e9189e7d7693aed1 (MD5) Previous issue date: 2011 / Resumo: Parasitos do filo Myxozoa (Grassé, 1970) estão entre os patógenos de peixes mais importantes e têm sido objeto de muitos estudos nos últimos anos. O objetivo deste trabalho foi desenvolver estudos taxonômicos (baseado em análises morfológicas e moleculares), da interação parasito-hospedeiro (com base nas análises histológicas e ultra-estruturais) e filogenéticos de mixosporidios parasitos de Brycon hilarii oriundos de ambiente natural e sistemas de criação. Os peixes de ambiente natural foram obtidos no Pantanal Matogrossense e os de sistemas de criação em pisciculturas do Estado de São Paulo. Uma nova espécie de Myxobolus (Myxobolus oliveirai) foi descrita infectando os filamentos braquiais de B. hilarii oriundos de ambiente natural, mas não foi observada a ocorrência deste parasito nos sistemas de criação avaliados. Dos 216 espécimes de B. hilarii examinados (126 silvestres e 90 cultivadas), 38,1% dos espécimes selvagens (n = 48) estavam infectados. O parasito formou plasmódios alongados, cerca de 3 mm de comprimento, principalmente na ponta dos filamentos branquiais. Foi realizada a comparação morfológica de M. oliveirai com todas as espécies de Myxobolus descritas infectando hospedeiros da América do Sul, assim como praticamente todas as espécies até agora descritas considerando todos os continentes. O sequenciamento parcial do gene 18S rDNA revelou que as sequências obtidas do Myxobolus parasito de B. hilarii não corresponde a nenhum dos Myxozoa disponíveis no GenBank. Na análise filogenética, M. oliveirai constituiu um grupo monofilético com outras oito espécies: cinco espécies de Myxobolus parasitos de peixes mugilídeos, duas espécies parasitos de pangasiideos e uma parasito de Centrarchideo. Os valores das prevalências da infecção não revelaram diferenças significativas entre as estações seca e úmida nem entre hospedeiros machos e fêmeas / Abstract: Parasites of the phylum Myxozoa (Grassé, 1970) are among the most important pathogens of fish and have been subject of many studies in recent years. The aim of this study was to develop taxonomic studies (based on morphological and molecular), of the parasite-host interaction (based on histological and ultrastructural analysis) and phylogenetic of myxosporeans parasites of Brycon hilarii from natural environment and fish farms. The fish were obtained from natural environment in the Mato Grosso wetlands Brazil and fish farms in the state of São Paulo. A new species of Myxobolus (Myxobolus oliveirai) was described infecting the brachial filaments of B. hilarii from the natural environment, but did not observe the occurrence of this parasite in fish farms evaluated. Out of 216 B. hilarii specimens examined (126 wild and 90 cultivated), 38.1% of wild specimens (n = 48) were infected. The parasites form elongated plasmodia primarily in the tip of gill filaments, reaching about 3 mm in length. A thorough comparison with all the Myxobolus species described from South American hosts, as well as nearly all the Myxobolus species described so far is provided. Partial sequencing of the 18S rDNA gene revealed that the Myxobolus species parasite of B. hilarii did not match any of the Myxozoa available in GenBank. In the phylogenetic analysis, M. oliveirai sp. nov. composed a monophyletic group with eight other species: five species of Myxobolus parasites of mugilid fishes, two parasites of pangasiid and one of centrarchid. Infection prevalence values of the parasite revealed no significant differences between wet and dry seasons or between males and females / Mestrado / Parasitologia / Mestre em Parasitologia

Myxobolus cerebralis, a myxozoan parasite of salmonids, is the causative agent of whirling disease. The parasite is considered widespread throughout northeastern Oregon in the Grande Ronde and Imnaha River basins where threatened and endangered salmonid populations exist. The work presented in this thesis comprises several studies that assess the effects of M. cerebralis on resident and anadromous salmonids in Oregon. Laboratory challenges to determine the susceptibility of indigenous Deschutes River, Oregon, salmonids to M. cerebralis were conducted as part of a study to assess the risk of reintroducing anadromous salmon above a migration barrier on that river. This study was the first to assess the susceptibility of kokanee salmon Oncorhynchus nerka to M. cerebralis, and results contribute to the understanding of salmonid susceptibility as it relates to species and age. Further, this study demonstrates that the indigenous salmonids present in the river are susceptible to infection, but resident rainbow trout Oncorhynchus mykiss would be most at risk should introduction of M. cerebralis occur in this system. The susceptibility of chinook salmon Oncorhynchus tshawytscha to M. cerebralis was assessed following laboratory challenges at different ages to different parasite levels. Results from this study indicate that chinook salmon are more resistant to M. cerebralis infection than susceptible rainbow trout; resistance to disease developed in chinook salmon exposed after 3 weeks of age. Sustained exposures to a low parasite dose were performed to model the conditions chinook salmon would encounter in a natural exposure. Following continuous exposure to low parasite densities, chinook salmon were very resistant to infection and disease. Managed populations of chinook salmon and steelhead Oncorhynchus mykiss juveniles are held in acclimation facilities on their natal streams before release to commence their seaward migration. Rainbow trout fry were held at each of the acclimation facilities to detect the presence of M. cerebralis and to assess the prevalence of exposure during the acclimation period. Results from these exposures indicate that the Wallowa acclimation facility is a high-risk site for parasite exposure of steelhead juveniles. Further, detection was confirmed in several rivers and streams where the presence of M. cerebralis has been suggested. Finally, a preliminary study on the effect of M. cerebralis on survival of steelhead juveniles upon transfer to saltwater was conducted. Results from this study indicate that M. cerebralis exposure and infection may increase mortality among juvenile steelhead during saltwater adaptation. / Graduation date: 2003

The genus Ceratomyxa Thélohan, 1892 is one of the largest myxozoan genera, the species of which almost always infect the gall bladder of marine teleosts. Although there are over 180 species known globally, prior to this study only three had been described from Australia. This study explores the systematics, host specificity and species richness of Ceratomyxa species from a diverse range of Queensland marine fishes. The first part of this thesis deals with the issues associated with spore based taxonomy and incorporates the first molecular studies to investigate host specificity and radiation in three common families of Great Barrier Reef (GBR) fishes. Twenty-two new species were described in these chapters, and although they were superficially similar in morphology all were genetically distinct. A focus on Ceratomyxa spp. infecting labrid, pomacentrid and serranid fish revealed tight host specificity of parasite species, confirmed the presence of multiple parasite species in a single host and revealed that no parasite radiation had occurred that could be associated with co-evolution with host families. Exploration of intra- and inter-specific variation by sequencing of multiple replicates from host/parasite combinations allowed interpretation of species boundaries within the system. Ten additional species described in Chapter 5 supported the findings from the labrid, pomacentrid and serranid studies but broadened the host range studied. In total 32 Ceratomyxa species were described from Queensland fishes increasing the number of described species in the genus by 15%. This study also reports on undescribed species collected from a further 70 host species and broadens the known host range to seven families of fishes. A checklist of bivalvulidans from marine teleosts in Australia is compiled of described and undescribed species and highlights the abundance of Ceratomyxa relative to other gall bladder dwelling myxosporeans. A phylogeny of the Ceratomyxa based on SSU rDNA analyses explored the taxonomic integrity of the genus. In general, the morphological diagnostic characters that divide the Myxozoa into genera are not well supported by molecular phylogenetic analyses. The relationship between 42 Ceratomyxa spp. and 36 other marine myxosporeans was examined using Bayesian inference, maximum likelihood and maximum parsimony. Results indicate Ceratomyxa is one of the most cohesive lineages within the Myxozoa and that the freshwater fish parasite, C. shasta, does not represent an independent lineage as suggested in previous studies. The strict host specificity of Ceratomyxa species prompted the investigation of species richness on the GBR. Species accumulation curves were used to explore species richness by using Choa2 and Jackknife1 estimators. The estimates suggested Ceratomyxa is almost as rich as their teleost hosts and that 1,600 species could be present on the GBR and as many as 15,000 species may exist globally. As an unexpected result, Ceratomyxa may be the richest metazoan genus in the sea. In light of what the study revealed, a revision of a second genus within the family Ceratomyxidae, Leptotheca, is presented. The boundaries between Ceratomyxa and Leptotheca were unclear. The diagnostic characters that separate these genera (length to thickness ratios) were found to be plastic and the type species of Leptotheca ultimately fitted the diagnosis for Ceratomyxa. To eliminate confusion between these genera and also between Sphaerospora and Leptotheca, the genus Leptotheca was considered invalid, with all species appropriately assigned to other genera based on morphological and biological characters and supported by genetic evidence.

The genus Ceratomyxa Thélohan, 1892 is one of the largest myxozoan genera, the species of which almost always infect the gall bladder of marine teleosts. Although there are over 180 species known globally, prior to this study only three had been described from Australia. This study explores the systematics, host specificity and species richness of Ceratomyxa species from a diverse range of Queensland marine fishes. The first part of this thesis deals with the issues associated with spore based taxonomy and incorporates the first molecular studies to investigate host specificity and radiation in three common families of Great Barrier Reef (GBR) fishes. Twenty-two new species were described in these chapters, and although they were superficially similar in morphology all were genetically distinct. A focus on Ceratomyxa spp. infecting labrid, pomacentrid and serranid fish revealed tight host specificity of parasite species, confirmed the presence of multiple parasite species in a single host and revealed that no parasite radiation had occurred that could be associated with co-evolution with host families. Exploration of intra- and inter-specific variation by sequencing of multiple replicates from host/parasite combinations allowed interpretation of species boundaries within the system. Ten additional species described in Chapter 5 supported the findings from the labrid, pomacentrid and serranid studies but broadened the host range studied. In total 32 Ceratomyxa species were described from Queensland fishes increasing the number of described species in the genus by 15%. This study also reports on undescribed species collected from a further 70 host species and broadens the known host range to seven families of fishes. A checklist of bivalvulidans from marine teleosts in Australia is compiled of described and undescribed species and highlights the abundance of Ceratomyxa relative to other gall bladder dwelling myxosporeans. A phylogeny of the Ceratomyxa based on SSU rDNA analyses explored the taxonomic integrity of the genus. In general, the morphological diagnostic characters that divide the Myxozoa into genera are not well supported by molecular phylogenetic analyses. The relationship between 42 Ceratomyxa spp. and 36 other marine myxosporeans was examined using Bayesian inference, maximum likelihood and maximum parsimony. Results indicate Ceratomyxa is one of the most cohesive lineages within the Myxozoa and that the freshwater fish parasite, C. shasta, does not represent an independent lineage as suggested in previous studies. The strict host specificity of Ceratomyxa species prompted the investigation of species richness on the GBR. Species accumulation curves were used to explore species richness by using Choa2 and Jackknife1 estimators. The estimates suggested Ceratomyxa is almost as rich as their teleost hosts and that 1,600 species could be present on the GBR and as many as 15,000 species may exist globally. As an unexpected result, Ceratomyxa may be the richest metazoan genus in the sea. In light of what the study revealed, a revision of a second genus within the family Ceratomyxidae, Leptotheca, is presented. The boundaries between Ceratomyxa and Leptotheca were unclear. The diagnostic characters that separate these genera (length to thickness ratios) were found to be plastic and the type species of Leptotheca ultimately fitted the diagnosis for Ceratomyxa. To eliminate confusion between these genera and also between Sphaerospora and Leptotheca, the genus Leptotheca was considered invalid, with all species appropriately assigned to other genera based on morphological and biological characters and supported by genetic evidence.

The genus Ceratomyxa Thélohan, 1892 is one of the largest myxozoan genera, the species of which almost always infect the gall bladder of marine teleosts. Although there are over 180 species known globally, prior to this study only three had been described from Australia. This study explores the systematics, host specificity and species richness of Ceratomyxa species from a diverse range of Queensland marine fishes. The first part of this thesis deals with the issues associated with spore based taxonomy and incorporates the first molecular studies to investigate host specificity and radiation in three common families of Great Barrier Reef (GBR) fishes. Twenty-two new species were described in these chapters, and although they were superficially similar in morphology all were genetically distinct. A focus on Ceratomyxa spp. infecting labrid, pomacentrid and serranid fish revealed tight host specificity of parasite species, confirmed the presence of multiple parasite species in a single host and revealed that no parasite radiation had occurred that could be associated with co-evolution with host families. Exploration of intra- and inter-specific variation by sequencing of multiple replicates from host/parasite combinations allowed interpretation of species boundaries within the system. Ten additional species described in Chapter 5 supported the findings from the labrid, pomacentrid and serranid studies but broadened the host range studied. In total 32 Ceratomyxa species were described from Queensland fishes increasing the number of described species in the genus by 15%. This study also reports on undescribed species collected from a further 70 host species and broadens the known host range to seven families of fishes. A checklist of bivalvulidans from marine teleosts in Australia is compiled of described and undescribed species and highlights the abundance of Ceratomyxa relative to other gall bladder dwelling myxosporeans. A phylogeny of the Ceratomyxa based on SSU rDNA analyses explored the taxonomic integrity of the genus. In general, the morphological diagnostic characters that divide the Myxozoa into genera are not well supported by molecular phylogenetic analyses. The relationship between 42 Ceratomyxa spp. and 36 other marine myxosporeans was examined using Bayesian inference, maximum likelihood and maximum parsimony. Results indicate Ceratomyxa is one of the most cohesive lineages within the Myxozoa and that the freshwater fish parasite, C. shasta, does not represent an independent lineage as suggested in previous studies. The strict host specificity of Ceratomyxa species prompted the investigation of species richness on the GBR. Species accumulation curves were used to explore species richness by using Choa2 and Jackknife1 estimators. The estimates suggested Ceratomyxa is almost as rich as their teleost hosts and that 1,600 species could be present on the GBR and as many as 15,000 species may exist globally. As an unexpected result, Ceratomyxa may be the richest metazoan genus in the sea. In light of what the study revealed, a revision of a second genus within the family Ceratomyxidae, Leptotheca, is presented. The boundaries between Ceratomyxa and Leptotheca were unclear. The diagnostic characters that separate these genera (length to thickness ratios) were found to be plastic and the type species of Leptotheca ultimately fitted the diagnosis for Ceratomyxa. To eliminate confusion between these genera and also between Sphaerospora and Leptotheca, the genus Leptotheca was considered invalid, with all species appropriately assigned to other genera based on morphological and biological characters and supported by genetic evidence.