Proteomic analysis of Neobenedenia sp. and Rhabdosynochus viridisi (Monogenea, Monopisthocotylea): Insights into potential vaccine targets and diagnostic markers for finfish aquaculture.

Monogeneans are parasitic flatworms that represent a significant threat to the aquaculture industry. Species like Neobenedenia melleni (Capsalidae) and Rhabdosynochus viridisi (Diplectanidae) have been identified as causing diseases in farmed fish. In the past years, molecular research on monogeneans of the subclass Monopisthocotylea has focused on the generation of genomic and transcriptomic information and the identification in silico of some protein families of veterinary interest. Proteomic analysis has been suggested as a powerful tool to investigate proteins in parasites and identify potential targets for vaccine development and diagnosis. To date, the proteomic dataset for monogeneans has been restricted to a species of the subclass Polyopisthocotylea, while in monopisthocotyleans there is no proteomic data. In this study, we present the first proteomic data on two monopisthocotylean species, Neobenedenia sp. and R. viridisi, obtained from three distinct sample types: tissue, excretory-secretory products (ESPs), and eggs. A total of 1691 and 1846 expressed proteins were identified in Neobenedenia sp. and R. viridisi, respectively. The actin family was the largest protein family, followed by the tubulin family and the heat shock protein 70 (HSP70) family. We focused mainly on ESPs because they are important to modulate the host immune system. We identified proteins of the actin, tubulin, HSP70 and HSP90 families in both tissue and ESPs, which have been recognized for their antigenic activities in parasitic flatworms. Furthermore, our study uncovered the presence of proteins within ESPs, such as annexin, calcium-binding protein, fructose bisphosphate aldolase, glutamate dehydrogenase, myoferlin, and paramyosin, that are targets for immunodiagnostic and vaccine development and hold paramount relevance in veterinary medicine. This study expands our knowledge of monogeneans and identified proteins that, in other platyhelminths are potential targets for vaccines and drug discovery.

Low similarity between parasite communities of ten sympatric carangid species.

Host phylogeny and ecological convergence are two factors thought to influence the structure of parasite communities. The aims of this study were to determine the diversity of metazoan parasites of 10 sympatric fish species of the family Carangidae from the southeastern Gulf of California, and to analyze their similarity at infracommunity and component community levels, in order to determine if the host species, particularly those congeneric with similar ecological characteristics, exhibit similar assemblages of parasites. In total, 874 fish specimens were examined and 40 parasite species were identified. The component community was composed by 21 parasite species in Caranx caninus, 20 in C. caballus, 11 in C. vinctus, five in Chloroscombrus orqueta, four in Carangoides otrynter, seven in Hemicaranx leucurus, eight in Selene brevoortii, 14 in S. peruviana, and 11 in Trachinotus rhodopus. The metazoan parasite communities of C. vinctus, Ch. orqueta, H. leucurus, and S. brevoortii are reported here for the first time. The parasite communities of the remaining six carangid species have been reported from regions other than the Gulf of California. All fish species differed significantly regarding the diversity of their parasite infracommunities. This possibly is due to different patterns of habitat use among fish species, and because of the differential host specificity among parasite taxa. Nonetheless, when the analysis was restricted to common parasite species, some fish showed similar parasite infracommunities, particularly congeners of the genus Selene as well as C. caballus and C. vinctus. The component communities of species of Selene were highly similar (>65%), but the three species of Caranx were not. This result supports the hypothesis that congeneric fish species with similar ecological filters harbor similar parasite communities. However, the difference observed between C. caninus and C. caballus suggests that these species, despite being evolutionary and ecologically related, have different physiological or immunological characteristics (compatibility filters) that may result in different parasite communities.

Exploring Evolutionary Relationships within Neodermata Using Putative Orthologous Groups of Proteins, with Emphasis on Peptidases.

The phylogenetic relationships within Neodermata were examined based on putative orthologous groups of proteins (OGPs) from 11 species of Monogenea, Trematoda, and Cestoda. The dataset included OGPs from BUSCO and OMA. Additionally, peptidases were identified and evaluated as phylogenetic markers. Phylogenies were inferred using the maximum likelihood method. A network analysis and a hierarchical grouping analysis of the principal components (HCPC) of orthologous groups of peptidases were performed. The phylogenetic analyses showed the monopisthocotylean monogeneans as the sister-group of cestodes, and the polyopisthocotylean monogeneans as the sister-group of trematodes. However, the sister-group relationship between Monopisthocotylea and Cestoda was not statistically well supported. The network analysis and HCPC also showed a cluster formed by polyopisthocotyleans and trematodes. The present study supports the non-monophyly of Monogenea. An analysis of mutation rates indicated that secreted peptidases and inhibitors, and those with multiple copies, are under positive selection pressure, which could explain the expansion of some families such as C01, C19, I02, and S01. Whilst not definitive, our study presents another point of view in the discussion of the evolution of Neodermata, and we hope that our data drive further discussion and debate on this intriguing topic.

The Efficacy of Geraniol and ß-Citronellol against Freshwater and Marine Monogeneans.

Monogeneans are parasitic flatworms that may be a threat for finfish aquaculture. In this study, the anthelmintic activity of two terpenes, geraniol and ß-citronellol, was tested in vitro against ancyrocephalin and diplectanid monogeneans. Experiments were performed in both water and a culture medium. We observed that monogeneans in culture medium may be more tolerant to treatments compared with bioassays performed only in water. Concentrations of 300 mg/L of both compounds were required to kill 100% of monogeneans at 1 h postexposure. The toxicity of ß-citronellol to fish was not evaluated. However, geraniol at 300 mg/L and 150 mg/L killed juvenile Nile Tilapia Oreochromis niloticus and White Snook Centropomus viridis, respectively, after a few minutes. Therefore, the present work suggests that other alternatives should be studied for use against monogeneans in aquaculture.

In vitro efficacy of two terpenes against ancyrocephalid monogeneans from Nile tilapia.

Terpenes are naturally produced compounds with a broad range of biological activities. Currently, there is limited information regarding the anthelminthic effect of terpenes against monogenean parasites of fish. The aim of this work was to evaluate the in vitro efficacy of two terpenes [α-terpinene and (+)-limonene oxide] against ancyrocephalid monogeneans found on farmed Nile tilapia (Oreochromis niloticus). (+)-Limonene oxide was more effective in killing these parasites than α-terpinene, with 86 and 90% mortality at concentrations of 36 and 55.4 mg/L, respectively, with a 5-h treatment. The estimated 5-h EC50 of (+)-limonene oxide was 4.8 mg/L. Even though this compound has the potential to be used as an anthelmintic compound in finfish aquaculture, before in vivo experiments are performed, additional studies are needed to find a more effective concentration, as well as to evaluate other terpenic compounds.

Rapid infection and proliferation of dactylogyrid monogeneans on gills of spotted rose snapper (Lutjanus guttatus) after transfer to a sea-cage.

Finfish mariculture is typically threatened by parasite and disease outbreaks. Therefore, it is important to identify parasite species of potential risk for this activity. Snappers are valuable food fish worldwide. In the Eastern Pacific, spotted rose snapper (Lutjanus guttatus [Steindachner, 1869]) is a firm candidate for sea-cage aquaculture. In the current study, the parasitism of caged L. guttatus by dactylogyrids was evaluated for the first time during a complete farming period. Twenty five thousand juvenile fish produced at the Research Center for Food and Development (CIAD, Mazatlan Unit) were reared in a sentinel sea-cage from February to November 2012 in Mazatlan Bay, Mexico. A fish sample (n=15) was obtained every month. Dactylogyrids from the left second gill arch were identified and quantified. A total of 18,704 dactylogyrids distributed in three species, Euryhaliotrema perezponcei García-Vargas, Fajer-Ávila and Lamothe-Argumedo, 2008, E. mehen (Soler-Jiménez, García-Gasca and Fajer-Ávila, 2012), and Haliotrematoides guttati García-Vargas, Fajer-Ávila and Lamothe-Argumedo, 2008 (Monogenea: Dactylogyridae) was found, which were able to infect caged L. guttatus since the first month of the farming period. Prevalence of these parasite species was 100% all the time, except for initial low values for E. mehen and H. guttati. The mean intensity of infection of each dactylogyrid species varied significantly between sampling months. Euryhaliotrema perezponcei was the most abundant parasite, reaching the highest mean intensity in May, June and July (154.3, 296.9 and 176.6 parasites/host, respectively). No clear seasonality of infection was observed; however, the influence of the water temperature on the observed infection levels is discussed. There was no mortality, change on behavior or pathological signs. However, given the rapid infection and proliferation of dactylogyrids, particularly E. perezponcei on L. guttaus reared in a sentinel sea-cage, outbreak of these parasites could be expected when this fish species is cultured on a large scale.

Redescription of Caligus serratus Shiino, 1965 (Copepoda: Caligidae) parasitic on eleven fish species from Chamela Bay in the Mexican Pacific.

Caligus serratus Shiino, 1965 (Copepoda: Caligidae), a parasite on 11 fish species caught in Chamela Bay off the Pacific Coast of Mexico, is redescribed based on material found on Pacific agujon needlefish Tylosurus pacificus (Steindachner, 1876). Caligus serratus can be distinguished from its congeners by the combination of the following characters: i) short abdomen (approximately 0.2 times as long as cephalothorax), ii) pointed posteromedial process on the first segment of the antenna, iii) sternal furca with bluntly pointed, diverging tines, and iv) leg 4 exopod bearing 3 unequal, distal spines (the shortest 0.2 times the length of the longest). Microphotographs of female and illustrations of both female and male are provided. The redescription of this species might be useful given its low host specificity.