The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Frank Nilsen - One of the best experts on this subject based on the ideXlab platform.
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the potential for cleaner fish driven evolution in the Salmon Louse lepeophtheirus Salmonis genetic or environmental control of pigmentation
Ecology and Evolution, 2021Co-Authors: Lars Are Hamre, Frank Nilsen, Tina Oldham, Frode Oppedal, Kevin A GloverAbstract:The parasitic Salmon Louse represents one of the biggest challenges to environmentally sustainable Salmonid aquaculture across the globe. This species also displays a high evolutionary potential, as demonstrated by its rapid development of resistance to delousing chemicals. In response, farms now use a range of non-chemical delousing methods, including cleaner fish that eat lice from Salmon. Anecdotal reports suggest that in regions where cleaner fish are extensively used on farms, lice have begun to appear less pigmented and therefore putatively less visible to cleaner fish. However, it remains an open question whether these observations reflect a plastic (environmental) or adaptive (genetic) response. To investigate this, we developed a pigment scoring system and conducted complimentary experiments which collectively demonstrate that, a) Louse pigmentation is strongly influenced by environmental conditions, most likely light, and b) the presence of modest but significant differences in pigmentation between two strains of lice reared under identical conditions. Based on these data, we conclude that pigmentation in the Salmon Louse is strongly influenced by environmental conditions, yet there are also indications of underlying genetic control. Therefore, lice could display both plastic and adaptive responses to extensive cleaner fish usage where visual appearance is likely to influence survival of lice.
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gene co expression networks identify novel candidate genes for moulting and development in the atlantic Salmon Louse lepeophtheirus Salmonis
bioRxiv, 2021Co-Authors: Z Zhou, Frank Nilsen, Christiane Eichner, Inge Jonassen, Michael DondrupAbstract:Background: The Salmon Louse (Lepeophtheirus Salmonis) is an obligate ectoparasitic copepod, living on Atlantic Salmon and other Salmonids in the marine environment. Salmon lice cause a number of environmental problems and lead to large economical losses in aquaculture every year. In order to develop novel parasite control strategies, a better understanding of the mechanisms of moulting and development of the Salmon Louse at the transcriptional level is required. Methods: Three weighted gene co-expression networks were constructed based on the pairwise correlations of Salmon Louse gene expression profiles at different life stages. Network-based approaches and gene annotation information were applied to identify genes that might be important for the moulting and development of the Salmon Louse. RNA interference was performed for validation. Regulatory impact factors were calculated for all the transcription factor genes by examining the changes in co-expression patterns between transcription factor genes and deferentially expressed genes in middle stages and moulting stages. Results: Eight gene modules were predicted as important, and 10 genes from six of the eight modules have been found to show observable phenotypes in RNA interference experiments. We knocked down five hub genes from three modules and observed phenotypic consequences in all experiments. In the infection trial, no copepodids with the RAB1A-like gene knocked down were found on fish, while control samples developed to chalimus-1 larvae. Also, a FOXO-like gene obtained highest scores in the regulatory impact factor calculation. Conclusions: We propose a gene co-expression network-based approach to identify genes playing an important role in the moulting and development of Salmon Louse. The RNA interference experiments confirmed the effectiveness of our approach and demonstrated the indispensable role of RAB1A-like gene in the development of Salmon Louse. In addition to Salmon Louse, this approach could be generalized to identify important genes associated with a phenotype of interest in other organisms.
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gene co expression network analysis facilitates identification of novel important genes for the moulting process of the Salmon Louse lepeophtheirus Salmonis
bioRxiv, 2021Co-Authors: Z Zhou, Frank Nilsen, Christiane Eichner, Inge Jonassen, Michael DondrupAbstract:Abstract Background The Salmon Louse (Lepeophtheirus Salmonis) is an obligate ectoparasitic copepod, living on Atlantic Salmon and other Salmonids in the marine environment. Salmon lice cause a number of environmental problems and lead to large economical losses in aquaculture every year. In order to develop novel parasite control strategies, a better understanding of the mechanisms of moulting and development of the Salmon Louse at the transcriptional level is required. Method Three weighted gene co-expression networks were constructed based on the pairwise correlations of Salmon Louse gene expression profiles at different life stages. Network-based approaches and gene annotation information were applied to identify genes that might be important for the moulting and development of the Salmon Louse. RNA interference was performed for validation. Regulatory impact factors were calculated for all the transcription factor genes by examining the changes in co-expression patterns between transcription factor genes and deferentially expressed genes in middle stages and moulting stages. Results Eight gene modules were predicted as important, and 10 genes from six of the eight modules have been found to show observable phenotypes in RNA interference experiments. We knocked down five hub genes from three modules and observed phenotypic consequences in all experiments. In the infection trial, no copepodids with the RAB1A-like gene knocked down were found on fish, while control samples developed to chalimus-1 larvae. The FOXO-like gene obtained highest scores in the regulatory impact factor calculation. Conclusions We proposed a gene co-expression network-based approach to identify genes playing an important role in the moulting and development of Salmon Louse. The RNA interference experiments confirmed the effectiveness of our approach and demonstrated the indispensable role of RAB1A-like gene in the development of Salmon Louse. In addition to Salmon Louse, this approach could be generalized to identify important genes associated with a phenotype of interest in other organisms.
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host gill attachment causes blood feeding by the Salmon Louse lepeophtheirus Salmonis chalimus larvae and alters parasite development and transcriptome
Parasites & Vectors, 2020Co-Authors: Erna Irene Heggland, Frank Nilsen, Michael Dondrup, Christiane EichnerAbstract:Blood-feeding is a common strategy among parasitizing arthropods, including the ectoparasitic Salmon Louse (Lepeophtheirus Salmonis), feeding off its Salmon host’s skin and blood. Blood is rich in nutrients, among these iron and heme. These are essential molecules for the Louse, yet their oxidative properties render them toxic to cells if not handled appropriately. Blood-feeding might therefore alter parasite gene expression. We infected Atlantic Salmon with Salmon Louse copepodids and sampled the lice in two different experiments at day 10 and 18 post-infestation. Parasite development and presence of host blood in their intestines were determined. Lice of similar instar age sampled from body parts with differential access to blood, namely from gills versus lice from skin epidermis, were analysed for gene expression by RNA-sequencing in samples taken at day 10 for both experiments and at day 18 for one of the experiments. We found that lice started feeding on blood when becoming mobile preadults if sitting on the fish body; however, they may initiate blood-feeding at the chalimus I stage if attached to gills. Lice attached to gills develop at a slower rate. By differential expression analysis, we found 355 transcripts elevated in lice sampled from gills and 202 transcripts elevated in lice sampled from skin consistent in all samplings. Genes annotated with “peptidase activity” were among the ones elevated in lice sampled from gills, while in the other group genes annotated with “phosphorylation” and “phosphatase” were pervasive. Transcripts elevated in lice sampled from gills were often genes relatively highly expressed in the Louse intestine compared with other tissues, while this was not the case for transcripts elevated in lice sampled from skin. In both groups, more than half of the transcripts were from genes more highly expressed after attachment. Gill settlement results in an alteration in gene expression and a premature onset of blood-feeding likely causes the parasite to develop at a slower pace.
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identification and description of the key molecular components of the egg strings of the Salmon Louse lepeophtheirus Salmonis
Genes, 2019Co-Authors: Andreas Borchel, Heidi Kongshaug, Frank NilsenAbstract:The Salmon Louse Lepeophtheirus Salmonis is a parasite of Atlantic Salmon and other Salmonids. Every year, it causes high costs for the Norwegian aquaculture industry. While the morphology of the female genital tract has been described, knowledge of the molecular basis of reproduction is very limited. We identified nine genes which are expressed exclusively in the female cement gland, the organ responsible for cement production, which is used to hold the eggs together and keep them attached to their mother in egg strings. Six of these genes encode proteins with signal peptides and probably form the main component of the cement. Two other genes are peroxidases, which are probably important in the cement formation. The last gene is not similar to any known protein, but contains a transmembrane domain. A knockdown of all these genes leads to missing or deformed egg strings, preventing reproduction of the lice. The correct assemblage of the cement in the cement gland is essential for successful reproduction of Salmon lice. Similar proteins seem to be present in other copepod species, as well.
Sussie Dalvin - One of the best experts on this subject based on the ideXlab platform.
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the Salmon Louse genome copepod features and parasitic adaptations
bioRxiv, 2021Co-Authors: R Skernmauritzen, Sussie Dalvin, Christiane Eichner, Michael Dondrup, Anna Z Komisarczuk, Ketil Malde, Tomasz Furmanek, Francois Besnier, M Nuhn, Rolf B EdvardsenAbstract:Arthropods comprise the most populous groups of animals and show an astonishing diversity. Aquatic arthropods belonging to the sub-class Copepoda encompass a range of ecological roles from endo- and ectoparasites to grazers of phytoplankton that link primary producers to higher trophic levels. Despite the important role of copepods in central ecosystem services and their impact as parasites, representative genomic data and genome assemblies are scarce. This limits our opportunities to understand both the specific biology of individual species and unifying copepod genomic features that may govern their capacities to, for example, adapt to a changing environment. Among the copepod parasites we find Lepeophtheirus Salmonis, an important ectoparasite that represents a threat to wild Salmonid stocks and causes large annual losses to the Salmon farming industry. Here we present the Salmon Louse genome - the first genome of a parasitic copepod that is fully sequenced and annotated. The 695.4 Mbp assembly was validated by a genetic linkage map and comprises 13 autosomes that recombine almost exclusively in males, one autosome that is shielded from recombination in both sexes and a ZZ-ZW style sex chromosome system. The genome assembly contains approximate 60% repetitive regions and comprise 13081 annotated predicted protein-coding genes. The predicted gene set appears to be quite complete as 92.4% of the expected Arthropod genes were found by a BUSCO. The gene annotations were validated by transcriptome sequencing that corresponds to the expected function of selected tissues. Transcriptome sequencing further revealed a marked shift in the gene expression pattern at the transition from the planktonic dispersal phase to the parasitic lifestyle after host attachment. Among other features, genes related to circadian rhythm are downregulated upon attaching to a host - probably reflecting abandoning a planktonic life with diurnal migration. The genome shows several evolutionary signatures including a large expansion of FNII domains, commonly considered vertebrate specific, and an incomplete heme homeostasis pathway suggesting that heme proteins are obtained from the host. The Salmon Louse has repeatedly demonstrated a large capacity to develop resistance against chemical treatments. Nonetheless, it exhibits low reduced numbers of several genes commonly involved in detoxification; cytochrome P450, ATP-Binding Cassette type transporters and Glutathione S-transferases. Interestingly, only one gene family with a putative detoxification role was expanded: the major vault proteins. Finally, the Salmon Louse has lost the ability to sustain peroxisomes, a loss apparently shared in the Caligid family but not among copepods in general.
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molecular characterization and functional analysis of components of the tor pathway of the Salmon Louse lepeophtheirus Salmonis kroyer 1838
Experimental Parasitology, 2018Co-Authors: Liv Sandlund, Frank Nilsen, Heidi Kongshaug, Sussie DalvinAbstract:Abstract The Salmon Louse Lepeophtheirus Salmonis (Copepods, Caligida) is a marine ectoparasite infecting Salmonid fishes in the northern hemisphere. At present, Salmon lice infections are the most severe disease problem in the Salmon farming industry causing significant economic losses. Due to development of resistance towards available chemotherapeutants, it is clear that new chemotherapeutants or non-chemical control methods are essential to manage the parasite in the future. The TOR signaling pathway is present in all metazoans and is a major regulator of cellular activity according to nutrient availability. In this study, we identified the TOR pathway genes in Salmon Louse; LsTSC1, LsTSC2, LsRheb, LsTOR, LsRaptor and LsRictor. RNA interference mediated gene silencing was performed to elucidate the functional role of each member of the pathway. Our results show that interference of the TOR signaling pathway either directly or indirectly inhibits many biological processes including egg maturation. In addition, the effect of gene knock-down results in more comprehensive physiological defects when targeting TORC1 and the upstream regulator Rheb. This is the first report on the TOR pathway in the Salmon Louse and that our research contributes to the basic knowledge of the parasite that could lead to development of novel treatment methods.
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molecular characterization of the lipophorin receptor in the crustacean ectoparasite lepeophtheirus Salmonis
PLOS ONE, 2018Co-Authors: Muhammad Tanveer Khan, Frank Nilsen, Sussie Dalvin, Qaiser Waheed, Rune MaleAbstract:The Salmon Louse (Lepeophtheirus Salmonis) is a marine ectoparasite of Salmonid fish in the Northern Hemisphere and considered as a major challenge in aquaculture and a threat to wild populations of Salmonids. Adult female lice produce a large number of lipid-rich eggs, however, the mechanism of maternal lipid transport into developing eggs during Salmon Louse reproduction has not been described. In the present study, a full-length L. Salmonis lipophorin receptor (LsLpR) consisting of 16 exons was obtained by RACE and RT-PCR. The predicted ORF was 952 amino acids and structural analysis showed five functional domains that are similar to LpR of insects and decapods. Phylogenetic analysis placed the LsLpR together with LpRs from decapods and insects. Expression analysis revealed that the relative abundance of LsLpR transcripts was highest in the larvae and adult female lice. In adult females, the LsLpR transcripts and protein were found in the ovary and vitellogenic oocytes whereas, in larvae, the LsLpR transcripts were found in the neuronal somata of the brain and the intestine. Oil Red O stain results revealed that storage of neutral lipids was found in vitellogenic oocytes and ovaries of adult females, and in the yolk of larvae. Moreover, RNA interference (RNAi) was conducted to demonstrate the function of LsLpR in reproduction and lipid metabolism in L. Salmonis. In larvae, the transcription of LsLpR was decreased by 44-54% while in an experiment LsLpR knockdown female lice produced 72% less offspring than control lice.
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identification and characterisation of the ecdysone biosynthetic genes neverland disembodied and shade in the Salmon Louse lepeophtheirus Salmonis copepoda caligidae
PLOS ONE, 2018Co-Authors: Liv Sandlund, Frank Nilsen, Rune Male, Heidi Kongshaug, Tor Einar Horsberg, Sussie DalvinAbstract:The Salmon Louse is a marine ectoparasitic copepod on Salmonid fishes. Its lifecycle consists of eight developmental stages, each separated by a molt. In crustaceans and insects, molting and reproduction is controlled by circulating steroid hormones such as 20-hydroxyecdysone. Steroid hormones are synthesized from cholesterol through catalytic reactions involving a 7,8-dehydrogenase Neverland and several cytochrome P450 genes collectively called the Halloween genes. In this study, we have isolated and identified orthologs of neverland, disembodied and shade in the Salmon Louse (Lepeophtheirus Salmonis) genome. Tissue-specific expression analysis show that the genes are expressed in intestine and reproductive tissue. In addition, levels of the steroid hormones ecdysone, 20-hydroxyecdysone and ponasterone A were measured during the reproductive stage of adult females and in early life stages.
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characterization of three Salmon Louse lepeophtheirus Salmonis genes with fibronectin ii domains expressed by tegumental type 1 glands
Molecular and Biochemical Parasitology, 2018Co-Authors: Ewa Harasimczuk, Frank Nilsen, Sindre Grotmol, Ainacathrine Overgard, Sussie DalvinAbstract:The Salmon Louse, Lepeophtheirus Salmonis (Copepoda: Caligidae), is currently the most significant pathogen affecting the Salmon farming industry in the Northern Hemisphere. Exocrine glands of blood-feeding parasites are believed to be important for the host-parasite interaction, but also in the production of substances for integument lubrication and antifouling. In L. Salmonis; however, we have limited knowledge about the exocrine glands. The aim of this study was therefore to examine three genes containing fibronectin type II (FNII) domains expressed in L. Salmonis tegumental type 1 (teg 1) glands, namely LsFNII1, 2 and 3. LsFNII1, 2 and 3 contains four, three, and two FNII domains respectively. Sequence alignment of LsFNII domains showed conservation of amino acids that may indicate a possible involvement of LsFNII domains in collagen binding. Ontogenetic analysis of LsFNII1, 2 and 3 revealed highest expression in pre-adult and adult lice. Localization of LsFNII1, 2 and 3 transcripts showed expression in teg 1 glands only, which are the most abundant exocrine gland type in L. Salmonis. LsFNII1, 2 and 3 were successfully knocked-down by RNAi, however, alteration in gland morphology was not detected between the knock-down and control groups. Overall, this study gives first insight into FNII domain containing proteins in L. Salmonis.
Christiane Eichner - One of the best experts on this subject based on the ideXlab platform.
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the ftz f1 gene encodes two functionally distinct nuclear receptor isoforms in the ectoparasitic copepod Salmon Louse lepeophtheirus Salmonis
PLOS ONE, 2021Co-Authors: Joakim Brunet, Christiane Eichner, Rune MaleAbstract:The Salmon Louse, Lepeophtheirus Salmonis, is an ectoparasitic crustacean that annually inflicts substantial losses to the aquaculture industry in the northern hemisphere and poses a threat to the wild populations of Salmonids. The Salmon Louse life cycle consists of eight developmental stages each separated by a molt. Fushi Tarazu Factor-1 (FTZ-F1) is an ecdysteroid-regulated gene that encodes a member of the NR5A family of nuclear receptors that is shown to play a crucial regulatory role in molting in insects and nematodes. Characterization of an FTZ-F1 orthologue in the Salmon Louse gave two isoforms named αFTZ-F1 and βFTZ-F1, which are identical except for the presence of a unique N-terminal domain (A/B domain). A comparison suggest conservation of the FTZ-F1 gene structure among ecdysozoans, with the exception of nematodes, to produce isoforms with unique N-terminal domains through alternative transcription start and splicing. The two isoforms of the Salmon Louse FTZ-F1 were expressed in different amounts in the same tissues and showed a distinct cyclical expression pattern through the molting cycle with βFTZ-F1 being the highest expressed isoform. While RNA interference knockdown of βFTZ-F1 in nauplius larvae and in pre-adult males lead to molting arrest, knockdown of βFTZ-F1 in pre-adult II female lice caused disruption of oocyte maturation at the vitellogenic stage. No apparent phenotype could be observed in αFTZ-F1 knockdown larvae, or in their development to adults, and no genes were found to be differentially expressed in the nauplii larvae following αFTZ-F1 knockdown. βFTZ-F1 knockdown in nauplii larvae caused both down and upregulation of genes associated with proteolysis and chitin binding and affected a large number of genes which are in normal Salmon Louse development expressed in a cyclical pattern. This is the first description of FTZ-F1 gene function in copepod crustaceans and provides a foundation to expand the understanding of the molecular mechanisms of molting in the Salmon Louse and other copepods.
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gene co expression networks identify novel candidate genes for moulting and development in the atlantic Salmon Louse lepeophtheirus Salmonis
bioRxiv, 2021Co-Authors: Z Zhou, Frank Nilsen, Christiane Eichner, Inge Jonassen, Michael DondrupAbstract:Background: The Salmon Louse (Lepeophtheirus Salmonis) is an obligate ectoparasitic copepod, living on Atlantic Salmon and other Salmonids in the marine environment. Salmon lice cause a number of environmental problems and lead to large economical losses in aquaculture every year. In order to develop novel parasite control strategies, a better understanding of the mechanisms of moulting and development of the Salmon Louse at the transcriptional level is required. Methods: Three weighted gene co-expression networks were constructed based on the pairwise correlations of Salmon Louse gene expression profiles at different life stages. Network-based approaches and gene annotation information were applied to identify genes that might be important for the moulting and development of the Salmon Louse. RNA interference was performed for validation. Regulatory impact factors were calculated for all the transcription factor genes by examining the changes in co-expression patterns between transcription factor genes and deferentially expressed genes in middle stages and moulting stages. Results: Eight gene modules were predicted as important, and 10 genes from six of the eight modules have been found to show observable phenotypes in RNA interference experiments. We knocked down five hub genes from three modules and observed phenotypic consequences in all experiments. In the infection trial, no copepodids with the RAB1A-like gene knocked down were found on fish, while control samples developed to chalimus-1 larvae. Also, a FOXO-like gene obtained highest scores in the regulatory impact factor calculation. Conclusions: We propose a gene co-expression network-based approach to identify genes playing an important role in the moulting and development of Salmon Louse. The RNA interference experiments confirmed the effectiveness of our approach and demonstrated the indispensable role of RAB1A-like gene in the development of Salmon Louse. In addition to Salmon Louse, this approach could be generalized to identify important genes associated with a phenotype of interest in other organisms.
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gene co expression network analysis facilitates identification of novel important genes for the moulting process of the Salmon Louse lepeophtheirus Salmonis
bioRxiv, 2021Co-Authors: Z Zhou, Frank Nilsen, Christiane Eichner, Inge Jonassen, Michael DondrupAbstract:Abstract Background The Salmon Louse (Lepeophtheirus Salmonis) is an obligate ectoparasitic copepod, living on Atlantic Salmon and other Salmonids in the marine environment. Salmon lice cause a number of environmental problems and lead to large economical losses in aquaculture every year. In order to develop novel parasite control strategies, a better understanding of the mechanisms of moulting and development of the Salmon Louse at the transcriptional level is required. Method Three weighted gene co-expression networks were constructed based on the pairwise correlations of Salmon Louse gene expression profiles at different life stages. Network-based approaches and gene annotation information were applied to identify genes that might be important for the moulting and development of the Salmon Louse. RNA interference was performed for validation. Regulatory impact factors were calculated for all the transcription factor genes by examining the changes in co-expression patterns between transcription factor genes and deferentially expressed genes in middle stages and moulting stages. Results Eight gene modules were predicted as important, and 10 genes from six of the eight modules have been found to show observable phenotypes in RNA interference experiments. We knocked down five hub genes from three modules and observed phenotypic consequences in all experiments. In the infection trial, no copepodids with the RAB1A-like gene knocked down were found on fish, while control samples developed to chalimus-1 larvae. The FOXO-like gene obtained highest scores in the regulatory impact factor calculation. Conclusions We proposed a gene co-expression network-based approach to identify genes playing an important role in the moulting and development of Salmon Louse. The RNA interference experiments confirmed the effectiveness of our approach and demonstrated the indispensable role of RAB1A-like gene in the development of Salmon Louse. In addition to Salmon Louse, this approach could be generalized to identify important genes associated with a phenotype of interest in other organisms.
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the Salmon Louse genome copepod features and parasitic adaptations
bioRxiv, 2021Co-Authors: R Skernmauritzen, Sussie Dalvin, Christiane Eichner, Michael Dondrup, Anna Z Komisarczuk, Ketil Malde, Tomasz Furmanek, Francois Besnier, M Nuhn, Rolf B EdvardsenAbstract:Arthropods comprise the most populous groups of animals and show an astonishing diversity. Aquatic arthropods belonging to the sub-class Copepoda encompass a range of ecological roles from endo- and ectoparasites to grazers of phytoplankton that link primary producers to higher trophic levels. Despite the important role of copepods in central ecosystem services and their impact as parasites, representative genomic data and genome assemblies are scarce. This limits our opportunities to understand both the specific biology of individual species and unifying copepod genomic features that may govern their capacities to, for example, adapt to a changing environment. Among the copepod parasites we find Lepeophtheirus Salmonis, an important ectoparasite that represents a threat to wild Salmonid stocks and causes large annual losses to the Salmon farming industry. Here we present the Salmon Louse genome - the first genome of a parasitic copepod that is fully sequenced and annotated. The 695.4 Mbp assembly was validated by a genetic linkage map and comprises 13 autosomes that recombine almost exclusively in males, one autosome that is shielded from recombination in both sexes and a ZZ-ZW style sex chromosome system. The genome assembly contains approximate 60% repetitive regions and comprise 13081 annotated predicted protein-coding genes. The predicted gene set appears to be quite complete as 92.4% of the expected Arthropod genes were found by a BUSCO. The gene annotations were validated by transcriptome sequencing that corresponds to the expected function of selected tissues. Transcriptome sequencing further revealed a marked shift in the gene expression pattern at the transition from the planktonic dispersal phase to the parasitic lifestyle after host attachment. Among other features, genes related to circadian rhythm are downregulated upon attaching to a host - probably reflecting abandoning a planktonic life with diurnal migration. The genome shows several evolutionary signatures including a large expansion of FNII domains, commonly considered vertebrate specific, and an incomplete heme homeostasis pathway suggesting that heme proteins are obtained from the host. The Salmon Louse has repeatedly demonstrated a large capacity to develop resistance against chemical treatments. Nonetheless, it exhibits low reduced numbers of several genes commonly involved in detoxification; cytochrome P450, ATP-Binding Cassette type transporters and Glutathione S-transferases. Interestingly, only one gene family with a putative detoxification role was expanded: the major vault proteins. Finally, the Salmon Louse has lost the ability to sustain peroxisomes, a loss apparently shared in the Caligid family but not among copepods in general.
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host gill attachment causes blood feeding by the Salmon Louse lepeophtheirus Salmonis chalimus larvae and alters parasite development and transcriptome
Parasites & Vectors, 2020Co-Authors: Erna Irene Heggland, Frank Nilsen, Michael Dondrup, Christiane EichnerAbstract:Blood-feeding is a common strategy among parasitizing arthropods, including the ectoparasitic Salmon Louse (Lepeophtheirus Salmonis), feeding off its Salmon host’s skin and blood. Blood is rich in nutrients, among these iron and heme. These are essential molecules for the Louse, yet their oxidative properties render them toxic to cells if not handled appropriately. Blood-feeding might therefore alter parasite gene expression. We infected Atlantic Salmon with Salmon Louse copepodids and sampled the lice in two different experiments at day 10 and 18 post-infestation. Parasite development and presence of host blood in their intestines were determined. Lice of similar instar age sampled from body parts with differential access to blood, namely from gills versus lice from skin epidermis, were analysed for gene expression by RNA-sequencing in samples taken at day 10 for both experiments and at day 18 for one of the experiments. We found that lice started feeding on blood when becoming mobile preadults if sitting on the fish body; however, they may initiate blood-feeding at the chalimus I stage if attached to gills. Lice attached to gills develop at a slower rate. By differential expression analysis, we found 355 transcripts elevated in lice sampled from gills and 202 transcripts elevated in lice sampled from skin consistent in all samplings. Genes annotated with “peptidase activity” were among the ones elevated in lice sampled from gills, while in the other group genes annotated with “phosphorylation” and “phosphatase” were pervasive. Transcripts elevated in lice sampled from gills were often genes relatively highly expressed in the Louse intestine compared with other tissues, while this was not the case for transcripts elevated in lice sampled from skin. In both groups, more than half of the transcripts were from genes more highly expressed after attachment. Gill settlement results in an alteration in gene expression and a premature onset of blood-feeding likely causes the parasite to develop at a slower pace.
Cristian Gallardoescarate - One of the best experts on this subject based on the ideXlab platform.
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microrna biogenesis pathway from the Salmon Louse caligus rogercresseyi emerging role in delousing drug response
Gene, 2015Co-Authors: Diego Valenzuelamiranda, Gustavo Nunezacuna, Valentina Valenzuelamunoz, Sassan Asgari, Cristian GallardoescarateAbstract:Despite the increasing evidence of the importance of microRNAs (miRNAs) in the regulation of multiple biological processes, the molecular bases supporting this regulation are still barely understood in crustaceans. Therefore, the molecular characterization and transcriptome modulation of the miRNA biogenesis pathway were evaluated in the Salmon Louse Caligus rogercresseyi, an ectoparasite that constitutes one of the biggest concerns for Salmonid aquaculture industry. Hence, RNA-Seq analysis was conducted from six different developmental stages, and also after bioassays with delousing drugs Deltamethrin and Azamethiphos using adult individuals. In silico analysis evidenced 24 putative genes involved in the miRNA pathway such as biogenesis, transport, maturation and miRNA-target interaction. Moreover, 243 putative single nucleotide polymorphisms (SNPs) were identified, 15 of which showed non-synonym mutations. RNA-Seq analysis revealed that CCR4-Not complex subunit 3 (CNOT3) was upregulated at earlier developmental stages (nauplius I-II and copepodid), and also after the exposure to Azamethiphos, but not to Deltamethrin. In contrast, the subunit 7 (CNOT7) showed an inverse expression pattern. Different Argonaute transcripts were associated to chalimus and adult stages, revealing specific expression patterns in response to antiparasitic drugs. Our results suggest novel insights into the regulatory network of the post-transcriptional gene regulation in C. rogercresseyi mediated by miRNAs, evidencing a putative role during the ontogeny and drug response.
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discovery of sex related genes through high throughput transcriptome sequencing from the Salmon Louse caligus rogercresseyi
Marine Genomics, 2014Co-Authors: Rodolfo Farlora, Jose Miguel Arayagaray, Cristian GallardoescarateAbstract:Understanding the molecular underpinnings involved in the reproduction of the Salmon Louse is critical for designing novel strategies of pest management for this ectoparasite. However, genomic information on sex-related genes is still limited. In the present work, sex-specific gene transcription was revealed in the Salmon Louse Caligus rogercresseyi using high-throughput Illumina sequencing. A total of 30,191,914 and 32,292,250 high quality reads were generated for females and males, and these were de novo assembled into 32,173 and 38,177 contigs, respectively. Gene ontology analysis showed a pattern of higher expression in the female as compared to the male transcriptome. Based on our sequence analysis and known sex-related proteins, several genes putatively involved in sex differentiation, including Dmrt3, FOXL2, VASA, and FEM1, and other potentially significant candidate genes in C. rogercresseyi, were identified for the first time. In addition, the occurrence of SNPs in several differentially expressed contigs annotating for sex-related genes was found. This transcriptome dataset provides a useful resource for future functional analyses, opening new opportunities for sea lice pest control.
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high throughput snp discovery and transcriptome expression profiles from the Salmon Louse caligus rogercresseyi copepoda caligidae
Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2014Co-Authors: Gustavo Nunezacuna, Valentina Valenzuelamunoz, Cristian GallardoescarateAbstract:The Salmon Louse Caligus rogercresseyi is the dominant ectoparasite species affecting the Salmon aquaculture industry in the Southern hemisphere, and it is currently the main cause for economic losses in Chilean aquaculture. However, despite the great concern over Caligus infestations, genomic information on this Louse is still scarce, even while the need to develop high-resolution molecular markers is growing. This study provides the first deep transcriptome survey to identify thousands of SNP markers from C. rogercresseyi, with a total of 69,466 SNPs identified using the MiSeq platform (Illumina®), 30,605 (52%) of which were found in contigs successfully annotated against known protein databases. Furthermore, in silico gene expression profiles associated with SNP variants were evaluated, and the results evidenced a wide array of genes that were down- and upregulated throughout the developmental stages of C. rogercresseyi. Interestingly, putative KEGG pathways involved in resistance to antiparasitic agents were also identified, where ten pathways were associated with the nervous system and one was related to ABC transporters. Taken together, this information could be highly useful for investigating the molecular underpinnings involved in the susceptibility or resistance of Salmon lice to chemical treatments.
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increasing transcriptome response of serpins during the ontogenetic stages in the Salmon Louse caligus rogercresseyi copepoda caligidae
Marine Genomics, 2014Co-Authors: W Maldonadoaguayo, Cristian GallardoescarateAbstract:Serine protease inhibitors, or serpins, target serine proteases, and are important regulators of intra- and extracellular proteolysis. For parasite survival, parasite-derived protease inhibitors have been suggested to play essential roles in evading the host's immune system and protecting against exogenous host proteases. The aim of this work was to identify serpins via high throughput transcriptome sequencing and elucidate their potential functions during the lifecycle of the Salmon Louse Caligus rogercresseyi. Eleven putative, partial serpin sequences in the C. rogercresseyi transcriptome were identified and denoted as Cr-serpins 1 to 11. Comparative analysis of the deduced serpin-like amino acid sequences revealed a highly conserved reactive center loop region. Interestingly, P1 residues suggest putative functions involved with the trypsin/subtilisin, elastase, or subtilisin inhibitors, which evidenced increasing gene expression profiles from the copepodid to adult stage in C. rogercresseyi. Concerning this, Cr-serpin 10 was mainly expressed in the copepodid stage, while Cr-serpins 3, 4, 5, and 11 were mostly expressed in chalimus and adult stages. These results suggest that serpins could be involved in evading the immune response of the host fish. The identification of these serpins furthers the understanding of the immune system in this important ectoparasite species.
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rna seq analysis using de novo transcriptome assembly as a reference for the Salmon Louse caligus rogercresseyi
PLOS ONE, 2014Co-Authors: Cristian Gallardoescarate, Valentina Valenzuelamunoz, Gustavo NunezacunaAbstract:Despite the economic and environmental impacts that sea lice infestations have on Salmon farming worldwide, genomic data generated by high-throughput transcriptome sequencing for different developmental stages, sexes, and strains of sea lice is still limited or unknown. In this study, RNA-seq analysis was performed using de novo transcriptome assembly as a reference for evidenced transcriptional changes from six developmental stages of the Salmon Louse Caligus rogercresseyi. EST-datasets were generated from the nauplius I, nauplius II, copepodid and chalimus stages and from female and male adults using MiSeq Illumina sequencing. A total of 151,788,682 transcripts were yielded, which were assembled into 83,444 high quality contigs and subsequently annotated into roughly 24,000 genes based on known proteins. To identify differential transcription patterns among Salmon Louse stages, cluster analyses were performed using normalized gene expression values. Herein, four clusters were differentially expressed between nauplius I–II and copepodid stages (604 transcripts), five clusters between copepodid and chalimus stages (2,426 transcripts), and six clusters between female and male adults (2,478 transcripts). Gene ontology analysis revealed that the nauplius I–II, copepodid and chalimus stages are mainly annotated to aminoacid transfer/repair/breakdown, metabolism, molting cycle, and nervous system development. Additionally, genes showing differential transcription in female and male adults were highly related to cytoskeletal and contractile elements, reproduction, cell development, morphogenesis, and transcription-translation processes. The data presented in this study provides the most comprehensive transcriptome resource available for C. rogercresseyi, which should be used for future genomic studies linked to host-parasite interactions.
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trends in de lousing of norwegian farmed Salmon from 2000 2019 consumption of medicines Salmon Louse resistance and non medicinal control methods
PLOS ONE, 2020Co-Authors: Elena Myhre Jensen, Tor Einar Horsberg, Sigmund Sevatdal, Kari Olli HelgesenAbstract:The Salmon Louse Lepeophtheirus Salmonis has been a substantial obstacle in Norwegian farming of Atlantic Salmon for decades. With a limited selection of available medicines and frequent delousing treatments, resistance has emerged among Salmon lice. Surveillance of Salmon Louse sensitivity has been in place since 2013, and consumption of medicines has been recorded since the early 80's. The peak year for Salmon lice treatments was 2015, when 5.7 times as many tonnes of Salmonids were treated compared to harvested. In recent years, non-medicinal methods of delousing farmed fish have been introduced to the industry. By utilizing data on the annual consumption of medicines, annual frequency of medicinal and non-medicinal treatments, the aim of the current study was to describe the causative factors behind Salmon lice sensitivity in the years 2000-2019, measured through toxicity tests-bioassays. The sensitivity data from 2000-2012 demonstrate the early emergence of resistance in Salmon lice along the Norwegian coast. Reduced sensitivity towards azamethiphos, deltamethrin and emamectin benzoate was evident from 2009, 2009 and 2007, respectively. The annual variation in medicine consumption and frequency of medicinal treatments correlated well with the evolution in Salmon Louse sensitivity. The patterns are similar, with a relatively small response delay from the decline in the consumption of medicines in Norway (2016 and onward) to the decline in measured resistance among Salmon Louse (2017 and onward). 2017 was the first year in which non-medicinal treatments outnumbered medicinal delousing treatments as well as the peak year in numbers of cleanerfish deployed. This study highlights the significance of avoiding heavy reliance on a few substance groups to combat ectoparasites, this can be a potent catalyst for resistance evolution. Further, it demonstrates the importance of transparency in the global industry, which enables the industry to learn from poor choices in the past.
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candidate genes for monitoring hydrogen peroxide resistance in the Salmon Louse lepeophtheirus Salmonis
Parasites & Vectors, 2020Co-Authors: Celia Agustiridaura, Kari Olli Helgesen, Marit Jorgensen Bakke, Arvind Y M Sundaram, Sigrid Jorgensen Bakke, Kiranpreet Kaur, Tor Einar HorsbergAbstract:Hydrogen peroxide (H2O2) is one of the delousing agents used to control sea lice infestations in Salmonid aquaculture. However, some Lepeophtheirus Salmonis populations have developed resistance towards H2O2. An increased gene expression and activity of catalase, an enzyme that breaks down H2O2, have been detected in resistant lice, being therefore introduced as a resistance marker in the Salmon industry. In the present study the aim was to validate the use of catalase expression as a marker and to identify new candidate genes as additional markers to catalase, related to H2O2 resistance in L. Salmonis. A sensitive and an H2O2 resistant laboratory strain (P0 generation, not exposed to H2O2 for several years) were batch crossed to generate a cohort with a wide range of H2O2 sensitivities (F2 generation). F2 adult females were then exposed to H2O2 to separate sensitive and resistant individuals. Those F2 lice, the P0 lice and field-collected resistant lice (exposed to H2O2 in the field) were used in an RNA sequencing study. Catalase was upregulated in resistant lice exposed to H2O2 compared to sensitive lice. This was, however, not the case for unexposed resistant P0 lice. Several other genes were found differentially expressed between sensitive and resistant lice, but most of them seemed to be related to H2O2 exposure. However, five genes were consistently up- or downregulated in the resistant lice independent of exposure history. The upregulated genes were: one gene in the DNA polymerase family, one gene encoding a Nesprin-like protein and an unannotated gene encoding a small protein. The downregulated genes encoded endoplasmic reticulum resident protein 29 and an aquaporin (Glp1_v2). Catalase expression seems to be induced by H2O2 exposure, since it was not upregulated in unexposed resistant lice. This may pose a challenge for its use as a resistance marker. The five new genes associated with resistance are put forward as complementary candidate genes. The most promising was Glp1_v2, an aquaglyceroporin that may serve as a passing channel for H2O2. Lower channel number can reduce the influx or distribution of H2O2 in the Salmon Louse, being directly involved in the resistance mechanism.
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Quantitative risk assessment of Salmon Louse-induced mortality of seaward-migrating post-smolt Atlantic Salmon
Elsevier, 2018Co-Authors: Anja Bråthen Kristoffersen, Kari Olli Helgesen, Lars Qviller, Knut Wiik Vollset, Hildegunn Viljugrein, Peder Andreas JansenAbstract:The Norwegian government recently implemented a new management system to regulate Salmon farming in Norway, aiming to promote environmentally sustainable growth in the aquaculture industry. The Norwegian coast has been divided into 13 production zones and the volume of Salmonid production in the zones will be regulated based on Salmon lice effects on wild Salmonids. Here we present a model for assessing Salmon Louse-induced mortality of seaward-migrating post-smolts of Atlantic Salmon. The model quantifies expected Salmon lice infestations and Louse-induced mortality of migrating post-smolt Salmon from 401 Salmon rivers draining into Norwegian coastal waters. It is assumed that migrating post-smolts follow the shortest path from river outlets to the high seas, at constant progression rates. During this migration, fish are infested by Salmon lice of farm origin according to an empirical infestation model. Furthermore, Louse-induced mortality is estimated from the estimated Louse infestations. Rivers draining into production zones on the West Coast of Norway were at the highest risk of adverse lice effects. In comparison, rivers draining into northerly production zones, along with the southernmost production zone, were at lower risk. After adjusting for standing stock biomass, estimates of Louse-egg output varied by factors of up to 8 between production zones. Correlation between biomass adjusted output of Louse infestation and densities of farmed Salmon in the production zones suggests that a large-scale density-dependent host-parasite effect is a major driver of Louse infestation rates and parasite-induced mortality. The estimates are sensitive to many of the processes in the chain of events in the model. Nevertheless, we argue that the model is suited to assess spatial and temporal risks associated with farm-origin Salmon lice. Keywords: Density dependent, Sea lice, Transmission, Farmed Salmon, Migration pathway, Migration tim
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quantitative risk assessment of Salmon Louse induced mortality of seaward migrating post smolt atlantic Salmon
Epidemics, 2017Co-Authors: Anja B Kristoffersen, Kari Olli Helgesen, Lars Qviller, Knut Wiik Vollset, Hildegunn Viljugrein, Peder A JansenAbstract:The Norwegian government recently implemented a new management system to regulate Salmon farming in Norway, aiming to promote environmentally sustainable growth in the aquaculture industry. The Norwegian coast has been divided into 13 production zones and the volume of Salmonid production in the zones will be regulated based on Salmon lice effects on wild Salmonids. Here we present a model for assessing Salmon Louse-induced mortality of seaward-migrating post-smolts of Atlantic Salmon. The model quantifies expected Salmon lice infestations and Louse-induced mortality of migrating post-smolt Salmon from 401 Salmon rivers draining into Norwegian coastal waters. It is assumed that migrating post-smolts follow the shortest path from river outlets to the high seas, at constant progression rates. During this migration, fish are infested by Salmon lice of farm origin according to an empirical infestation model. Furthermore, Louse-induced mortality is estimated from the estimated Louse infestations. Rivers draining into production zones on the West Coast of Norway were at the highest risk of adverse lice effects. In comparison, rivers draining into northerly production zones, along with the southernmost production zone, were at lower risk. After adjusting for standing stock biomass, estimates of Louse-egg output varied by factors of up to 8 between production zones. Correlation between biomass adjusted output of Louse infestation and densities of farmed Salmon in the production zones suggests that a large-scale density-dependent host-parasite effect is a major driver of Louse infestation rates and parasite-induced mortality. The estimates are sensitive to many of the processes in the chain of events in the model. Nevertheless, we argue that the model is suited to assess spatial and temporal risks associated with farm-origin Salmon lice.
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first report of reduced sensitivity towards hydrogen peroxide found in the Salmon Louse lepeophtheirus Salmonis in norway
Aquaculture Reports, 2015Co-Authors: Kari Olli Helgesen, Harriet Romstad, Stian Morch Aaen, Tor Einar HorsbergAbstract:Reduced sensitivity towards chemotherapeutants in the Salmon Louse Lepeophtheirus Salmonis (Kroyer) is an increasing problem for the fish farming industry. Most fish farmers are dependent on chemical treatments in order to maintain Salmon lice numbers below permitted levels. However parasites showing reduced sensitivity contribute to complicating this task. Hydrogen peroxide (H2O2) is used as a delousing agent in bath treatments and until recently treatment failures due to reduced H2O2-sensitivity have not been documented in Norway. The aim of the current study was to develop a bioassay protocol suitable for testing H2O2-sensitivity in L. Salmonis. If failed treatments were found to be caused by parasite insensitivity to H2O2 the possibility of this reduced sensitivity being hereditary was looked into. The results show that bioassays permit differentiation between strains of Salmon lice with regards to H2O2-sensitivity, coinciding with treatment efficacies. Up to ten times variance in sensitivity between two strains was recorded. The progeny of the least sensitive Salmon lice also showed reduced sensitivity to H2O2 in a bioassay, which indicates that reduced sensitivity towards H2O2 is hereditary. The current study presents the first case report of reduced sensitivity towards H2O2 in Salmon lice in Norway. This change in sensitivity imposes a threat to the Norwegian fish farming industry and should be monitored closely.
