Identification of Transcripts Relating to Host-parasite Interactions and Feeding-associated Activities Through De Novo Transcriptome Sequencing of Branchiuran Fish Lice, Argulus Foliaceus (Linnaeus, 1758) and Argulus Coregoni Thorell, 1865

The genus Argulus comprises obligate ectoparasites known as “fish lice” that cause argulosis and significant mortalities in both wild and cultured fish populations. Our previous proteomic analysis confirmed the presence of immunomodulatory products in the secretory / excretory products (SEPs) of Argulus foliaceus (Linnaeus, 1758). In this study, high-throughput sequencing was employed on host-associated stages of A. foliaceus and A. coregoni Thorell, 1865, with comparisons made to a pre-existing transcriptome dataset for A. siamensis. A total of 84,256,934 reads assembled into 66,940 contigs for A. foliaceus, and 10,840,092 reads to give 40,954 contigs for A. coregoni, comprises the largest current genomic data set for the genus Argulus. GO analysis of the top 100 shared genes revealed A. coregoni to be phylogenetically more closely related to A. foliaceus than to A. siamensis. Using OrthoVenn software 6,674 shared gene clusters were identified, and a number of annotated proteins associated with feeding and immunomodulation in other parasites, including 25 trypsin proteins and 8 venom serine proteases amongst others, were discovered. This transcriptomic analysis has contributed to the identification of proteins / genes in Argulus, and the Branchiura more widely, previously characterised as being important immune mediators for other aquatic and terrestrial blood-feeding arthropods.

Identification of transcripts relating to host-parasite interactions and feeding-associated activities through de novo transcriptome sequencing of branchiuran fish lice, Argulus foliaceus (Linnaeus, 1758) and Argulus coregoni Thorell, 1865

BackgroundThe genus Argulus, whose members are widely known as “fish lice”, comprises a group of obligate ectoparasites that cause argulosis. This parasitic disease affects both wild and cultured fish populations and can lead to significant mortalities. Our previous work confirmed the presence of immunomodulatory or other active products in the secretions of Argulus foliaceus (Linnaeus, 1758) using proteomic analysis conducted on secretory / excretory products (SEPs). Some of the compounds identified have also been described for other host-associated Crustacea, particularly the parasitic copepod Lepeophtheirus salmonis (Krøyer, 1837). The identification and characterisation of such components can contribute to the understanding of the host-parasite relationship for argulids and may also assist in the development of novel control methods, however, due to limitations in existing genomic resources, only 27 proteins could be confirmed in SEPs. In this study, high-throughput sequencing, supported by the use of a range of bioinformatics tools and methodologies were employed on host-associated stages of A. foliaceus and A. coregoni Thorell, 1865 to explore elements of the transcriptome associated with host-parasite interactions and feeding-associated activities.ResultsThe transcriptome data produced in the current study comprises the largest current genomic data set for the genus Argulus, with 84,256,934 reads, assembled into 66,940 contigs for Argulus foliaceus, and 10,840,092 reads, assembled to give 40,954 contigs, representing the first transcript sequences for Argulus coregoni. A pre-existing transcriptome dataset for A. siamensis was also analysed. An overview of the functional roles of the transcripts and their respective proteins for the three Argulus species was performed using GO analysis. A phylogenetic tree was also constructed, using the top 100 shared genes for the four transcriptome datasets available for Argulus. From this analysis, A. coregoni was revealed to be more closely related to A. foliaceus than to A. siamensis. The application of OrthoVenn software to the Argulus spp. transcriptome datasets identified 6,674 shared gene clusters. The transcriptomic analysis in this study, supported by earlier proteome work, has contributed to identifying, for the first time, a range of proteins / genes in Argulus, and more widely for the Branchiura, that have been previously characterised as being important immune mediators for other aquatic and terrestrial blood-feeding arthropods. Data are available via EBI with the project number PRJEB34947.Conclusions In addition to confirming the presence of a range of key immune mediators in Argulus spp. for the first time, this study has provided important genomic tools for researchers seeking to better understand the biology and host interactions of Argulus spp. The created resources unlock the possibility of characterising protein targets relating to host-parasite interactions and feeding-associated activities and can thereby assist the future development of vaccines, veterinary drugs, functional feeds and other tools that might contribute to improved integrated pest management of these globally important parasites.

Features of the parasitic system formation in common carp in the aquaculture of the north-eastern and eastern regions of Ukraine

The research aimed to determine the peculiarities of the formation of the parasitic system in common carp in the aquaculture of the North-Eastern and Eastern regions of Ukraine. According to the results of the research, 27 species of parasites were found in common carp (12 — protozoa, 6 — monogeneans, 3 — trematodes, 2 — cestodes, 4 — parasitic crustaceans). Three species (11.1%) of registered parasites were invasive. 22 species (81.5%) of detected common carp’s parasites develop directly and 5 (18.5%) — with the participation of definitive and intermediate hosts. 26 species (96.3%) of common carp’s parasitic fauna were found in crucian carp and 21 species (77.8%) in other coarse fish species (roach, rudd, bleak, perch). It has been established that among the protozoa, pathogens from the genera Trichodina, Chilodonella, and Ichthyophthirius were of epizootic importance for young common carp; Eimeria carpelli, Ichthyobodo necator, Myxobolus ellipsoides, and Myxobolus dogieli had relevance. The level of prevalence in common carp fingerlings during outbreaks of chylodonelosis was 72%, two-year-olds — 65%, three-year-olds — 27%, during outbreaks of ichthyoftiriosis — 45%, 56%, and 24%, respectively. Prevalence of Trichodina acuta and Trichodina nigra in common carp fingerlings was, respectively, 52% and 38%, Ichthyobodo necator — 16%, Eimeria carpelli — 22%, Myxobolus ellipsoides, and Myxobolus dogieli — 17–18%. Among the pathogens of helminthic diseases in the aquaculture, monogenetic suckers (Dactylogyrus anchoratus, Dactylogyrus extensus, Dactylogyrus vastator, Gyrodactylus cyprini, and Gyrodactylus katharineri), as well as cestodes (Bothriocephalus acheilognathi and Khawia sinensis) were the most epizootic significance for common carp. Prevalence of parasites from the genus Dactylogyrus reached 68–87% in fingerlings, from the genus Gyrodactylus — 21–36%. The highest level of Bothriocephalus acheilognathi infection (82%) was registered in fingerlings. The maximum prevalence of Khawia sinensis (62%) was observed in two-year-olds. Outbreaks of diseases caused by crustaceans Lernaea cyprinacea and Argulus foliaceus with a high level of prevalence have been reported in fish from fingerlings to three-year-olds. The level of prevalence of Lernaea cyprinacea was 69%, Argulus foliaceus — 22%

Study of the effect of Nerium oleander extract in the destruction of Argulus foliaceus and Lernaea cyprinacea in ornamental fish

The effect of the extract of the Nerium oleander was studied on ornamental fish in vivo and in vitro, Using different concentrations and different periods. The results of the current study showed that the destruction of Argulus foliaceus in 50 g / 5 ml and 0.25 g / 5 ml of water after 62 and 135 minutes respectively when using the extract directly on the lice (in vitro), Lernaea cyprinacea was tested in the fish. The results of the study showed that Lernaea cyprinacea was destruction at a concentration of 50 mg/L after 15 minutes but did not affect lice, The results of the study showed that fish were cured from lice after one month of treatment at 33.33 mg/L for 72 consecutive hours. When fish were placed at 50/1500 g/L of the extract, they were treated from lice but caused the fish to die after 15 minutes after placing in a pure water bath.

The cost of infection: Argulus foliaceus and its impact on the swimming performance of the three-spined stickleback ( Gasterosteus aculeatus )

For fish, there can be multiple consequences of parasitic infections, including the physical impacts on swimming and the pathological costs of infection. This study used the three-spined stickleback ( Gasterosteus aculeatus ) and the ectoparasitic fish louse, Argulus foliaceus , to assess both physical (including form drag and mass) and pathological effects of infection. Both sustained (prolonged swimming within an open channel flume) and burst (C-start) swimming performance were measured on individual fish before (trials 1–2) and after infection (trials 3–5). Experimental infection occurred shortly before the third trial, when the physical impacts of infection could be separated from any subsequent pathology as transmission of adult parasites causes instantaneous drag effects prior to observable pathology. Despite the relatively large size of the parasite and corresponding increase in hydrodynamic drag for the host, there were no observable physical effects of infection on either sustained or burst host swimming. By contrast, parasite-induced pathology is the most probable explanation for reduced swimming performance across both tests. All sticklebacks displayed a preference for flow refugia, swimming in low-velocity regions of the flume, and this preference increased with both flow rate and infection time. This study suggests that even with large, physically demanding parasites their induced pathology is of greater concern than direct physical impact.

Metazoan Parasites and Health State of European Eel, Anguilla Anguilla (Anguilliformes, Anguillidae), From Tonga Lake and El Mellah Lagoon in the Northeast of Algeria

The aim of the study was to examine metazoans parasite communities of European eels (Anguilla anguilla) in freshwater (Tonga Lake) and brackish water (El Mellah lagoon) in the northeast of Algeria. Six parasite taxa were collected: one monogenean, Pseudodactylogyrus sp.; two crustaceans, Ergasilus sp. and Argulus foliaceus; two nematodes, Cucullanus sp. and Anguillicola crassus; one cestode, Bothriocephalus claviceps. Th e most prevalent parasite taxa in freshwater were Pseudodactylogyrus sp., A. crassus and Bothriocephalus claviceps; whereas in the brackish water, eels were infected mainly with A. crassus. Th e characteristics of the parasite component community structure revealed low parasite species diversity and high dominance values in eels from the two localities. Both communities were dominated by a single parasite species: Tonga eels by the monogenean Pseudodactylogyrus sp. and El Mellah lagoon eels by the nematode A. crassus, verified by high Berger-Parker dominance values of 0.76 and 0.87 respectively.