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Rosemary G Gillespie - One of the best experts on this subject based on the ideXlab platform.
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de novo characterization of the gene rich transcriptomes of two color polymorphic spiders Theridion grallator and t californicum araneae theridiidae with special reference to pigment genes
BMC Genomics, 2013Co-Authors: Peter J P Croucher, Geoff S Oxford, Michael S Brewer, Christopher J Winchell, Rosemary G GillespieAbstract:A number of spider species within the family Theridiidae exhibit a dramatic abdominal (opisthosomal) color polymorphism. The polymorphism is inherited in a broadly Mendelian fashion and in some species consists of dozens of discrete morphs that are convergent across taxa and populations. Few genomic resources exist for spiders. Here, as a first necessary step towards identifying the genetic basis for this trait we present the near complete transcriptomes of two species: the Hawaiian happy-face spider Theridion grallator and Theridion californicum. We mined the gene complement for pigment-pathway genes and examined differential expression (DE) between morphs that are unpatterned (plain yellow) and patterned (yellow with superimposed patches of red, white or very dark brown). By deep sequencing both RNA-seq and normalized cDNA libraries from pooled specimens of each species we were able to assemble a comprehensive gene set for both species that we estimate to be 98-99% complete. It is likely that these species express more than 20,000 protein-coding genes, perhaps 4.5% (ca. 870) of which might be unique to spiders. Mining for pigment-associated Drosophila melanogaster genes indicated the presence of all ommochrome pathway genes and most pteridine pathway genes and DE analyses further indicate a possible role for the pteridine pathway in theridiid color patterning. Based upon our estimates, T. grallator and T. californicum express a large inventory of protein-coding genes. Our comprehensive assembly illustrates the continuing value of sequencing normalized cDNA libraries in addition to RNA-seq in order to generate a reference transcriptome for non-model species. The identification of pteridine-related genes and their possible involvement in color patterning is a novel finding in spiders and one that suggests a biochemical link between guanine deposits and the pigments exhibited by these species.
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stabilizing selection maintains exuberant colour polymorphism in the spider Theridion californicum araneae theridiidae
Molecular Ecology, 2011Co-Authors: Peter J P Croucher, Geoff S Oxford, Rosemary G GillespieAbstract:Genetically controlled colour polymorphisms provide a physical manifestation of the operation of selection and how this can vary according to the spatial or temporal arrangement of phenotypes, or their frequency in a population. Here, we examine the role of selection in shaping the exuberant colour polymorphism exhibited by the spider Theridion californicum. This species is part of a system in which several distantly related spiders in the same lineage, but living in very different geographical areas, exhibit remarkably convergent polymorphisms. These polymorphisms are characterized by allelic inheritance and the presence of a single common cryptic morph and, in the case of T. californicum and its congener the Hawaiian happy-face spider Theridion grallator, numerous rare patterned morphs. We compare population differentiation estimated from colour phenotypic data to differentiation at neutral amplified fragment length polymorphisms (AFLP) loci and demonstrate that the colour polymorphism appears to be maintained by balancing selection. We also examine the patterns of selection in the genome-wide sample of AFLP loci and compare approaches to detecting signatures of selection in this context. Our results have important implications regarding balancing selection, suggesting that selective agents can act in a similar manner across disparate taxa in globally disjunct locales resulting in parallel evolution of exuberant polymorphism.
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molecular insights into the phylogenetic structure of the spider genus Theridion araneae theridiidae and the origin of the hawaiian Theridion like fauna
Zoologica Scripta, 2007Co-Authors: Mquel A Arnedo, Ingi Agnarsson, Rosemary G GillespieAbstract:The Hawaiian happy face spider (Theridion grallator Simon, 1900), named for a remarkable abdominal colour pattern resembling a smiling face, has served as a model organism for understanding the generation of genetic diversity. Theridion grallator is one of 11 endemic Hawaiian species of the genus reported to date. Asserting the origin of island endemics informs on the evolutionary context of diversification, and how diversity has arisen on the islands. Studies on the genus Theridion in Hawaii, as elsewhere, have long been hampered by its large size (> 600 species) and poor definition. Here we report results of phylogenetic analyses based on DNA sequences of five genes conducted on five diverse species of Hawaiian Theridion, along with the most intensive sampling of Theridiinae analysed to date. Results indicate that the Hawaiian Islands were colonised by two independent Theridiinae lineages, one of which originated in the Americas. Both lineages have undergone local diversification in the archipelago and have convergently evolved similar bizarre morphs. Our findings confirm para- or polyphyletic status of the largest Theridiinae genera: Theridion, Achaearanea and Chrysso. Convergent simplification of the palpal organ has occurred in the Hawaiian Islands and in two continental lineages. The results confirm the convergent evolution of social behaviour and web structure, both already documented within the Theridiidae. Greater understanding of phylogenetic relationships within the Theridiinae is key to understanding of behavioural and morphological evolution in this highly diverse group.
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quantum shifts in the genetic control of a colour polymorphism in Theridion grallator araneae theridiidae the hawaiian happy face spider
Heredity, 1996Co-Authors: Geoff S Oxford, Rosemary G GillespieAbstract:Quantum shifts in the genetic control of a colour polymorphism in Theridion grallator (Araneae: Theridiidae), the Hawaiian happy-face spider
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the effects of genetic background on the island specific control of a colour polymorphism in Theridion grallator araneae theridiidae the hawaiian happy face spider
Heredity, 1996Co-Authors: Geoff S Oxford, Rosemary G GillespieAbstract:The effects of genetic background on the island-specific control of a colour polymorphism in Theridion grallator (Araneae: Theridiidae), the Hawaiian happy-face spider
Geoff S Oxford - One of the best experts on this subject based on the ideXlab platform.
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de novo characterization of the gene rich transcriptomes of two color polymorphic spiders Theridion grallator and t californicum araneae theridiidae with special reference to pigment genes
BMC Genomics, 2013Co-Authors: Peter J P Croucher, Geoff S Oxford, Michael S Brewer, Christopher J Winchell, Rosemary G GillespieAbstract:A number of spider species within the family Theridiidae exhibit a dramatic abdominal (opisthosomal) color polymorphism. The polymorphism is inherited in a broadly Mendelian fashion and in some species consists of dozens of discrete morphs that are convergent across taxa and populations. Few genomic resources exist for spiders. Here, as a first necessary step towards identifying the genetic basis for this trait we present the near complete transcriptomes of two species: the Hawaiian happy-face spider Theridion grallator and Theridion californicum. We mined the gene complement for pigment-pathway genes and examined differential expression (DE) between morphs that are unpatterned (plain yellow) and patterned (yellow with superimposed patches of red, white or very dark brown). By deep sequencing both RNA-seq and normalized cDNA libraries from pooled specimens of each species we were able to assemble a comprehensive gene set for both species that we estimate to be 98-99% complete. It is likely that these species express more than 20,000 protein-coding genes, perhaps 4.5% (ca. 870) of which might be unique to spiders. Mining for pigment-associated Drosophila melanogaster genes indicated the presence of all ommochrome pathway genes and most pteridine pathway genes and DE analyses further indicate a possible role for the pteridine pathway in theridiid color patterning. Based upon our estimates, T. grallator and T. californicum express a large inventory of protein-coding genes. Our comprehensive assembly illustrates the continuing value of sequencing normalized cDNA libraries in addition to RNA-seq in order to generate a reference transcriptome for non-model species. The identification of pteridine-related genes and their possible involvement in color patterning is a novel finding in spiders and one that suggests a biochemical link between guanine deposits and the pigments exhibited by these species.
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stabilizing selection maintains exuberant colour polymorphism in the spider Theridion californicum araneae theridiidae
Molecular Ecology, 2011Co-Authors: Peter J P Croucher, Geoff S Oxford, Rosemary G GillespieAbstract:Genetically controlled colour polymorphisms provide a physical manifestation of the operation of selection and how this can vary according to the spatial or temporal arrangement of phenotypes, or their frequency in a population. Here, we examine the role of selection in shaping the exuberant colour polymorphism exhibited by the spider Theridion californicum. This species is part of a system in which several distantly related spiders in the same lineage, but living in very different geographical areas, exhibit remarkably convergent polymorphisms. These polymorphisms are characterized by allelic inheritance and the presence of a single common cryptic morph and, in the case of T. californicum and its congener the Hawaiian happy-face spider Theridion grallator, numerous rare patterned morphs. We compare population differentiation estimated from colour phenotypic data to differentiation at neutral amplified fragment length polymorphisms (AFLP) loci and demonstrate that the colour polymorphism appears to be maintained by balancing selection. We also examine the patterns of selection in the genome-wide sample of AFLP loci and compare approaches to detecting signatures of selection in this context. Our results have important implications regarding balancing selection, suggesting that selective agents can act in a similar manner across disparate taxa in globally disjunct locales resulting in parallel evolution of exuberant polymorphism.
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quantum shifts in the genetic control of a colour polymorphism in Theridion grallator araneae theridiidae the hawaiian happy face spider
Heredity, 1996Co-Authors: Geoff S Oxford, Rosemary G GillespieAbstract:Quantum shifts in the genetic control of a colour polymorphism in Theridion grallator (Araneae: Theridiidae), the Hawaiian happy-face spider
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the effects of genetic background on the island specific control of a colour polymorphism in Theridion grallator araneae theridiidae the hawaiian happy face spider
Heredity, 1996Co-Authors: Geoff S Oxford, Rosemary G GillespieAbstract:The effects of genetic background on the island-specific control of a colour polymorphism in Theridion grallator (Araneae: Theridiidae), the Hawaiian happy-face spider
R G Gillespie - One of the best experts on this subject based on the ideXlab platform.
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Genetics of a colour polymorphism in Theridion grallator (Araneae: Theridiidae), the Hawaiian happy-face spider, from Greater Maui
Heredity, 1996Co-Authors: G S Oxford, R G GillespieAbstract:Theridion grallator , the Hawaiian happy-face spider, a species endemic to four islands in the Hawaiian archipelago, exhibits an exuberant colour and pattern polymorphism involving both the carapace and opisthosoma (abdomen). Laboratory crosses and broods from wild-mated females demonstrate that the opisthosomal morphs on Maui (and probably on Moloka'i as well) act as if they are determined by alleles at one autosomal locus, although control by more than one linked locus cannot be eliminated. With the exception of the White morph, dominance results from the superimposition of one pattern on another. All morphs are found equally in males and females. Carapace morphs are also shown to be determined by alleles at one locus. The close association between particular carapace and opisthosomal patterns observed both in the field and in the laboratory is probably a result of linkage between loci rather than pleiotropic effects of alleles at one locus. A one-to-one matching of red- and black-pigmented areas on the opisthosoma with underlying guanine deposits, which produce a white backcloth against which the pigments are displayed, strongly suggests that the polymorphism in this species has evolved for its visual effects.
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Quantum shifts in the genetic control of a colour polymorphism in Theridion grallator (Araneae: Theridiidae), the Hawaiian happy-face spider
Heredity, 1996Co-Authors: G S Oxford, R G GillespieAbstract:Theridion grallator , the Hawaiian happy-face spider, endemic to four islands in the Hawaiian archipelago, exhibits an exuberant colour and pattern polymorphism involving both the carapace and opisthosoma (abdomen). Previous work has shown that on Maui (and probably on Moloka'i as well) all colour morphs act as if they are determined by alleles at one autosomal locus (although linked loci cannot be excluded) and all morphs are expressed equally in males and females. Here we demonstrate that on Hawai'i, the youngest island, Yellow and Red front morphs seem to be controlled by a single allele, sex-limited in expression, such that females are Yellow and males Red front. Red blob and Red ring form a similar pair of morphs, again apparently controlled by one allele, with Red blob confined to females, Red ring to males. Morphs Red front + back and Black ring are not sex-limited. Evidence from one brood indicates that two unlinked loci are involved in determining the colour polymorphism on Hawai'i. At least the sex-limitation of Yellow and Red front is shown to be island-wide and suggests that the quantum shifts in the genetic control of the polymorphism among islands probably trace their origins to the founding event when T. grallator colonized Hawai'i from Maui.
Egil Karlsbakk - One of the best experts on this subject based on the ideXlab platform.
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Desmozoon lepeophtherii (microsporidian) infections and pancreas disease (PD) outbreaks in farmed Atlantic salmon (Salmo salar L.)
Aquaculture, 2017Co-Authors: G.s. Gunnarsson, Heidrun Plarre, Egil Karlsbakk, Steffen H. Blindheim, Albert K. Imsland, Sigurd O. Handeland, Harald Sveier, Are NylundAbstract:Abstract An association between infections with the ubiquitous microsporidian Desmozoon lepeophtherii (D. lepeophtherii) and pancreas disease (PD) outbreaks has previously been suggested. We followed infections with D. lepeophtherii and salmonid alpha virus (SAV) in thirteen Atlantic salmon farms in western Norway during the first production year at sea. The purpose of the survey was to examine if the presence and density of infection with the microsporidian could be linked to severity of PD-infection. Since the microsporidian develops both in salmon and in salmon lice (Lepeophtheirus salmonis) and louse abundance varies geographically, we also examined the spatial and temporal distribution and density of D. lepeophtherii infections in farmed Atlantic salmon. The prevalence of D. lepeophtherii was 100% in all samples from all farms. D. lepeophtherii densities varied with season, peaking in autumn followed by a marked decrease in winter. Geographical differences between areas were observed in August, between the outer coast (salinity 23.5 ppt.) and the Hardangerfjord (inner area) (16.1 ppt.) with higher infection rates in the outer coastal areas. We likewise found that D. lepeophtherii density was significantly associated with the host condition factors; D. lepeophtherii density being significantly higher in salmon with low status. SAV infections occurred in six farms. Five of these developed — and were diagnosed with PD. No relationship was detected between D. lepeophtherii density, the detection of SAV or PD outbreaks over time. Statement of relevance This is an epizootiological study of Atlantic salmon, P. Theridion and SAV. There is much known about the pathogen in connection with disease outbreaks, but less is known about the occurrence of potential pathogen in healthy farmed salmon or how such infections develop over time. P. Theridion has been connected to SAV infection and PD outbreak. The result from this study does not support such connection. It appears that the SAV virus can persist in a farmed population at least 10 months prior to a PD outbreak. There is a connection between the salmon condition and density of P. Theridion where salmon with low condition has elevated density. This could identify P. Theridion as the agent possibly causing this condition.
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Temporal changes in infections with some pathogens associated with gill disease in farmed Atlantic salmon (Salmo salar L)
Aquaculture, 2017Co-Authors: G.s. Gunnarsson, Heidrun Plarre, Egil Karlsbakk, Steffen H. Blindheim, Albert K. Imsland, Sigurd O. Handeland, Harald Sveier, Are NylundAbstract:Abstract Gill disease (GD) in farmed Atlantic salmon may be due to the impact of several agents that may interact. We followed the infections of four gill disease-associated agents during the first year of production in six farms; examining the correlation between their densities in the gills. These farms were located in an area with high risk of developing gill disease, and three of the farms were diagnosed with GD in the autumn. In the present study we show temporal changes in pathogens in salmon from all 6 farms, revealing recurring infection patterns by Desmozoon lepeophtherii and Candidatus Branchiomonas cysticola (C. B. cysticola), and large variation without an apparent pattern in densities of Ichthyobodo salmonis . Infections with the microsporidian D. lepeophtherii show a clear seasonal pattern, and high densities are associated with GD. Ca. B. cysticola appears not to be directly connected to the disease, albeit densities of this bacterium may coincide with high D. lepeophtherii densities. Amoebae ( Paramoeba spp.) were only sporadically detected with low densities. Salmon with low condition had elevated densities of D. lepeophtherii and Ichthyobodo spp., while no such pattern was seen for the other pathogens. Challenge studies are needed to substantiate the role of D. lepeophtherii in GD, but realistic challenge model (i.e. bath) has so far not been developed. Based on the present molecular screening, we suggest that D. lepeophtherii infections both may be responsible for GD, and cause runting in farmed salmon populations. Statement of relevance This is an epizootiological study of Atlantic salmon and gill diseases. There is much known about pathogen in connection with GD outbreak, less is known about the occurrence of potential pathogen in healthy farmed salmon or how such infections develop over time. High densities of the microsporidian parasite Paranucleospora Theridion in the gills coincide with gill disease, making P. Theridion a possible primary source to this condition. Densities of Paranucleospora Theridion , Candidatus Branchiomonas cysticola and Ichthyobodo salmonis may be correlated in farmed salmon populations with gill disease. P.Theridion and I. salmonis densities are elevated in Atlantic salmon with low condition (‘runts’).
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Paranucleospora Theridion (Microsporidia) infection dynamics in farmed Atlantic salmon Salmo salar put to sea in spring and autumn
Diseases of Aquatic Organisms, 2012Co-Authors: Silje Sveen, Egil Karlsbakk, Hanne Øverland, Are NylundAbstract:The microsporidian Paranucleospora Theridion (syn. Desmozoon lepeophtheirii) is a parasite of Atlantic salmon Salmo salar and also a hyperparasite of the salmon louse Lepeophtheirus salmonis. The parasite develops 2 types of spores in salmon, cytoplasmic spores in phagocytes and intranuclear spores in epidermal cells. The former type of development is assumed to be propagative (autoinfection), while the epidermal spores transfer the parasite to lice. Development in lice is extensive, with the formation of xenoma-like hypertrophic cells filled with microsporidian spores. We show that salmon are infected in the absence of lice, likely through waterborne spores that initiate infections in the gills. During summer and autumn the parasite propagates in the kidney, as evidenced by peaking normalised expression of P. Theridion rRNA. Lice become infected during autumn, and develop extensive infections during winter. Lice mortality in winter and spring is likely responsible for a reservoir of spores in the water. Salmon transferred to sea in November (low temperature) did not show involvement of the kidney in parasite propagation and lice on such fish did not become infected. Apparently, low temperatures inhibit normal P. Theridion development in salmon.
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diseases of farmed atlantic salmon salmo salar associated with infections by the microsporidian paranucleospora Theridion
Diseases of Aquatic Organisms, 2011Co-Authors: Stian Nylund, Linda Andersen, I Saevareid, Heidrun Plarre, Kuninori Watanabe, Carl E Arnesen, Egil Karlsbakk, Are NylundAbstract:The microsporidian Paranucleospora Theridion was discovered in Atlantic salmon Salmo salar suffering from proliferative gill disease in a marine farm in western Norway in 2008. The para- site develops in cells of the reticuloendothelial system, cells important for normal immune function. The aim of this study was to see if P. Theridion could play a part in some of the diseases with unclear causes in salmon production in Norway, i.e. proliferative gill disease (PGI), pancreas disease (PD), heart and skeletal muscle inflammation (HSMI) and cardiomyopathy syndrome (CMS). P. Theridion was present in all areas with salmon farming in Norway, but high prevalence and densities of the par- asite in salmon and salmon lice were only seen in southern Norway. This region is also the main area for PGI and PD in Norway. Quantification of pathogens associated with PGI, PD, HSMI and CMS diagnoses showed that P. Theridion levels are high in southern Norway, and may therefore play a role in susceptibility and disease development. However, among the different diagnoses, fish with PGI are particularly heavily infected with P. Theridion. Therefore, P. Theridion appears as a possible primary agent in cases with high mortality in connection with PGI in western Norway.
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paranucleospora Theridion n gen n sp microsporidia enterocytozoonidae with a life cycle in the salmon louse lepeophtheirus salmonis copepoda and atlantic salmon salmo salar
Journal of Eukaryotic Microbiology, 2010Co-Authors: Stian Nylund, Kuninori Watanabe, Carl E Arnesen, Are Nylund, Egil KarlsbakkAbstract:ABSTRACT. Paranucleospora Theridion n. gen, n. sp., infecting both Atlantic salmon (Salmo salar) and its copepod parasite Lepeophtheirus salmonis is described. The microsporidian exhibits nuclei in diplokaryotic arrangement during all known life-cycle stages in salmon, but only in the merogonal stages and early sporogonal stage in salmon lice. All developmental stages of P. Theridion are in direct contact with the host cell cytoplasm or nucleoplasm. In salmon, two developmental cycles were observed, producing spores in the cytoplasm of phagocytes or epidermal cells (Cycle-I) and in the nuclei of epidermal cells (Cycle-II), respectively. Cycle-I spores are small and thin walled with a short polar tube, and are believed to be autoinfective. The larger oval intranuclear Cycle-II spores have a thick endospore and a longer polar tube, and are probably responsible for transmission from salmon to L. salmonis. Parasite development in the salmon louse occurs in several different cell types that may be extremely hypertrophied due to P. Theridion proliferation. Diplokaryotic merogony precedes monokaryotic sporogony. The rounded spores produced are comparable to the intranuclear spores in the salmon in most aspects, and likely transmit the infection to salmon. Phylogenetic analysis of P. Theridion partial rDNA sequences place the parasite in a position between Nucleospora salmonis and Enterocytozoon bieneusi. Based on characteristics of the morphology, unique development involving a vertebrate fish as well as a crustacean ectoparasite host, and the results of the phylogenetic analyses it is suggested that P. Theridion should be given status as a new species in a new genus.
Are Nylund - One of the best experts on this subject based on the ideXlab platform.
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Desmozoon lepeophtherii (microsporidian) infections and pancreas disease (PD) outbreaks in farmed Atlantic salmon (Salmo salar L.)
Aquaculture, 2017Co-Authors: G.s. Gunnarsson, Heidrun Plarre, Egil Karlsbakk, Steffen H. Blindheim, Albert K. Imsland, Sigurd O. Handeland, Harald Sveier, Are NylundAbstract:Abstract An association between infections with the ubiquitous microsporidian Desmozoon lepeophtherii (D. lepeophtherii) and pancreas disease (PD) outbreaks has previously been suggested. We followed infections with D. lepeophtherii and salmonid alpha virus (SAV) in thirteen Atlantic salmon farms in western Norway during the first production year at sea. The purpose of the survey was to examine if the presence and density of infection with the microsporidian could be linked to severity of PD-infection. Since the microsporidian develops both in salmon and in salmon lice (Lepeophtheirus salmonis) and louse abundance varies geographically, we also examined the spatial and temporal distribution and density of D. lepeophtherii infections in farmed Atlantic salmon. The prevalence of D. lepeophtherii was 100% in all samples from all farms. D. lepeophtherii densities varied with season, peaking in autumn followed by a marked decrease in winter. Geographical differences between areas were observed in August, between the outer coast (salinity 23.5 ppt.) and the Hardangerfjord (inner area) (16.1 ppt.) with higher infection rates in the outer coastal areas. We likewise found that D. lepeophtherii density was significantly associated with the host condition factors; D. lepeophtherii density being significantly higher in salmon with low status. SAV infections occurred in six farms. Five of these developed — and were diagnosed with PD. No relationship was detected between D. lepeophtherii density, the detection of SAV or PD outbreaks over time. Statement of relevance This is an epizootiological study of Atlantic salmon, P. Theridion and SAV. There is much known about the pathogen in connection with disease outbreaks, but less is known about the occurrence of potential pathogen in healthy farmed salmon or how such infections develop over time. P. Theridion has been connected to SAV infection and PD outbreak. The result from this study does not support such connection. It appears that the SAV virus can persist in a farmed population at least 10 months prior to a PD outbreak. There is a connection between the salmon condition and density of P. Theridion where salmon with low condition has elevated density. This could identify P. Theridion as the agent possibly causing this condition.
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Temporal changes in infections with some pathogens associated with gill disease in farmed Atlantic salmon (Salmo salar L)
Aquaculture, 2017Co-Authors: G.s. Gunnarsson, Heidrun Plarre, Egil Karlsbakk, Steffen H. Blindheim, Albert K. Imsland, Sigurd O. Handeland, Harald Sveier, Are NylundAbstract:Abstract Gill disease (GD) in farmed Atlantic salmon may be due to the impact of several agents that may interact. We followed the infections of four gill disease-associated agents during the first year of production in six farms; examining the correlation between their densities in the gills. These farms were located in an area with high risk of developing gill disease, and three of the farms were diagnosed with GD in the autumn. In the present study we show temporal changes in pathogens in salmon from all 6 farms, revealing recurring infection patterns by Desmozoon lepeophtherii and Candidatus Branchiomonas cysticola (C. B. cysticola), and large variation without an apparent pattern in densities of Ichthyobodo salmonis . Infections with the microsporidian D. lepeophtherii show a clear seasonal pattern, and high densities are associated with GD. Ca. B. cysticola appears not to be directly connected to the disease, albeit densities of this bacterium may coincide with high D. lepeophtherii densities. Amoebae ( Paramoeba spp.) were only sporadically detected with low densities. Salmon with low condition had elevated densities of D. lepeophtherii and Ichthyobodo spp., while no such pattern was seen for the other pathogens. Challenge studies are needed to substantiate the role of D. lepeophtherii in GD, but realistic challenge model (i.e. bath) has so far not been developed. Based on the present molecular screening, we suggest that D. lepeophtherii infections both may be responsible for GD, and cause runting in farmed salmon populations. Statement of relevance This is an epizootiological study of Atlantic salmon and gill diseases. There is much known about pathogen in connection with GD outbreak, less is known about the occurrence of potential pathogen in healthy farmed salmon or how such infections develop over time. High densities of the microsporidian parasite Paranucleospora Theridion in the gills coincide with gill disease, making P. Theridion a possible primary source to this condition. Densities of Paranucleospora Theridion , Candidatus Branchiomonas cysticola and Ichthyobodo salmonis may be correlated in farmed salmon populations with gill disease. P.Theridion and I. salmonis densities are elevated in Atlantic salmon with low condition (‘runts’).
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Paranucleospora Theridion (Microsporidia) infection dynamics in farmed Atlantic salmon Salmo salar put to sea in spring and autumn
Diseases of Aquatic Organisms, 2012Co-Authors: Silje Sveen, Egil Karlsbakk, Hanne Øverland, Are NylundAbstract:The microsporidian Paranucleospora Theridion (syn. Desmozoon lepeophtheirii) is a parasite of Atlantic salmon Salmo salar and also a hyperparasite of the salmon louse Lepeophtheirus salmonis. The parasite develops 2 types of spores in salmon, cytoplasmic spores in phagocytes and intranuclear spores in epidermal cells. The former type of development is assumed to be propagative (autoinfection), while the epidermal spores transfer the parasite to lice. Development in lice is extensive, with the formation of xenoma-like hypertrophic cells filled with microsporidian spores. We show that salmon are infected in the absence of lice, likely through waterborne spores that initiate infections in the gills. During summer and autumn the parasite propagates in the kidney, as evidenced by peaking normalised expression of P. Theridion rRNA. Lice become infected during autumn, and develop extensive infections during winter. Lice mortality in winter and spring is likely responsible for a reservoir of spores in the water. Salmon transferred to sea in November (low temperature) did not show involvement of the kidney in parasite propagation and lice on such fish did not become infected. Apparently, low temperatures inhibit normal P. Theridion development in salmon.
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diseases of farmed atlantic salmon salmo salar associated with infections by the microsporidian paranucleospora Theridion
Diseases of Aquatic Organisms, 2011Co-Authors: Stian Nylund, Linda Andersen, I Saevareid, Heidrun Plarre, Kuninori Watanabe, Carl E Arnesen, Egil Karlsbakk, Are NylundAbstract:The microsporidian Paranucleospora Theridion was discovered in Atlantic salmon Salmo salar suffering from proliferative gill disease in a marine farm in western Norway in 2008. The para- site develops in cells of the reticuloendothelial system, cells important for normal immune function. The aim of this study was to see if P. Theridion could play a part in some of the diseases with unclear causes in salmon production in Norway, i.e. proliferative gill disease (PGI), pancreas disease (PD), heart and skeletal muscle inflammation (HSMI) and cardiomyopathy syndrome (CMS). P. Theridion was present in all areas with salmon farming in Norway, but high prevalence and densities of the par- asite in salmon and salmon lice were only seen in southern Norway. This region is also the main area for PGI and PD in Norway. Quantification of pathogens associated with PGI, PD, HSMI and CMS diagnoses showed that P. Theridion levels are high in southern Norway, and may therefore play a role in susceptibility and disease development. However, among the different diagnoses, fish with PGI are particularly heavily infected with P. Theridion. Therefore, P. Theridion appears as a possible primary agent in cases with high mortality in connection with PGI in western Norway.
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paranucleospora Theridion n gen n sp microsporidia enterocytozoonidae with a life cycle in the salmon louse lepeophtheirus salmonis copepoda and atlantic salmon salmo salar
Journal of Eukaryotic Microbiology, 2010Co-Authors: Stian Nylund, Kuninori Watanabe, Carl E Arnesen, Are Nylund, Egil KarlsbakkAbstract:ABSTRACT. Paranucleospora Theridion n. gen, n. sp., infecting both Atlantic salmon (Salmo salar) and its copepod parasite Lepeophtheirus salmonis is described. The microsporidian exhibits nuclei in diplokaryotic arrangement during all known life-cycle stages in salmon, but only in the merogonal stages and early sporogonal stage in salmon lice. All developmental stages of P. Theridion are in direct contact with the host cell cytoplasm or nucleoplasm. In salmon, two developmental cycles were observed, producing spores in the cytoplasm of phagocytes or epidermal cells (Cycle-I) and in the nuclei of epidermal cells (Cycle-II), respectively. Cycle-I spores are small and thin walled with a short polar tube, and are believed to be autoinfective. The larger oval intranuclear Cycle-II spores have a thick endospore and a longer polar tube, and are probably responsible for transmission from salmon to L. salmonis. Parasite development in the salmon louse occurs in several different cell types that may be extremely hypertrophied due to P. Theridion proliferation. Diplokaryotic merogony precedes monokaryotic sporogony. The rounded spores produced are comparable to the intranuclear spores in the salmon in most aspects, and likely transmit the infection to salmon. Phylogenetic analysis of P. Theridion partial rDNA sequences place the parasite in a position between Nucleospora salmonis and Enterocytozoon bieneusi. Based on characteristics of the morphology, unique development involving a vertebrate fish as well as a crustacean ectoparasite host, and the results of the phylogenetic analyses it is suggested that P. Theridion should be given status as a new species in a new genus.
