Author: marina02

Description of multivalvulidan myxosporean parasites infecting marine fishes caught from Angolan waters

Multivalvulida myxosporeans of the genera Kudoa Meglitsch, 1947 and Unicapsula Davis, 1924 are commonly histozoic parasites of skeletal muscle of the estuarine and marine fishes [1]. They have been associated with post-mortem liquefaction of the muscles causing milky flesh and economic losses [2]. There is very few information regarding parasitic diseases caused by myxosporeans in southeast Atlantic fish. This study combines morphology, ultrastructure and molecular data to describe two parasites found in the skeletal muscle of teleost species with high commercial value and potential to be introduced into aquaculture.

Specimens of Pagellus bellottii Steindachner, 1882 (Red pandora) and Trachurus trecae Cadenat, 1950 (Cunene horse mackerel) were collected near the city of Luanda, Angola. Fish were dissected and their tissues and organs were macro and microscopically analyzed for the presence of myxosporeans. Infected samples were observed and photographed using light microscopy, and small fragments were prepared for transmission electron microscopy and sequencing of the 18S rRNA gene of the parasite using myxosporean-specific primers. The fish cytochrome oxidase subunit 1 gene was also sequenced to confirm host identity. Sequence construction, alignments, and phylogenetic analyses were performed using MEGA11.

In red pandora, myxospores composed of 3 valves and 3 polar capsules (one prominent and two rudimentary) were observed and classified as belonging to Unicapsula. BLASTn search matched this species to Unicapsula pflugfelderi. In Cunene horse mackerel, another multivalvulidan belonging to the genus Kudoa was observed. The myxospores of the latter were quadrangular in apical view, being comprised by 4 valves and 4 polar capsules, one being bigger than the others. The 18S rRNA sequence obtained from this parasite was 1,721 bp long and differed from congeneric species by more than 98.6%.

A new host record is reported for Unicapsula pflugfelderi Schubert, Sprague and Reinboth, 1975, previously described from sparid hosts in the Mediterranean [3]. In turn, the morphometric and molecular data obtained for the parasite infecting Trachurus trecae suggest that it may represent a potential new species of Kudoa. These findings constitute the first records of multivalvulidan myxosporeans in the ichthyofauna of Angola.

[1] Fiala I et al. (2015) In: Myxozoan Evolution, Ecology and Development, ed. Okamura B, Gruhl A and Bartholomew JL, (Springer, Switzerland), 69-84.

[2] Swearer SE and Roberston DR (1999) J Parasitol, 85: 337-353.

[3] Alama-Bermejo G et al. (2009) J Fish Dis, 32: 335-350.

Funding: This research was funded by National funds through FCT: project PTDC/BIA-BMA/6363/2020.

1. AZEVEDO, CARLOS, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Matosinhos, Portugal, Author
2. ANDRADE, NAHYMA, Faculty of Natural Sciences, University Agostinho Neto, Luanda, Angola, Author
3. ROCHA, SÓNIA, School of Medicine and Biomedical Sciences (ICBAS), University of Porto, Porto, Portugal, Author
4. ROCHA, SÓNIA, Institute for Research and Innovation in Health (i3S), University of Porto, Porto, Portugal, Author
5. CASAL, GRAÇA, UCIBIO—Applied Molecular Biosciences Unit, 1H-TOXRUN, IUCS-CESPU, Gandra, Portugal, Presenter
6. CASAL, GRAÇA, School of Medicine and Biomedical Sciences (ICBAS), University of Porto, Porto, Portugal, Presenter

Morphological and phylogenetic analysis of two Sphaerospora (sensu stricto) parasitizing the kidney of white seabream Diplodus sargus

Introduction: Myxosporeans are diverse endoparasitic cnidarians that primarily utilize fish as intermediate hosts. Members of the Sphaerospora (sensu stricto) lineage predominantly infect the urinary system of marine and freshwater fishes [1]. The white seabream (Diplodus sargus), a commercially important sparid in the Mediterranean and eastern Atlantic, has previously been reported to host myxosporean infections in the gallbladder [2] and urinary bladder [3], but none attributed to Sphaerospora.

Methodology: Reared D. sargus specimens were obtained from aquaculture facilities in southern Portugal. Their organs were examined microscopically, and parasitized tissues were processed for morphological studies and sequencing of the myxosporean 18S rDNA. Distance estimation and maximum likelihood analyses were conducted using MEGA 11.

Results: Two distinct Sphaerospora morphotypes were identified in the kidney. One morphotype produced larger myxospores, which were subspherical with a pointed apical end. Their valves were smooth with a posterior bulge, and united along a straight and prominent suture. Polar capsules were subspherical, each containing a polar tubule coiled in 5-6 turns. The second, smaller morphotype produced myxospores that were thicker than wide, almost ellipsoid-like. Their valves were similarly united along a straight suture, but each exhibited an inconspicuous posterolateral bulge. Polar capsules were also subspherical, but the number of polar tubule coils could not be determined. Morphological comparisons revealed no significant similarity to other Sphaerospora. Distance estimation showed the highest similarity (96.4%) between the two morphotypes, and 80.1–90.3% similarity to Sphaerospora sparidarum (JX286620) from Sparus aurata (Sparidae). Consistently, maximum likelihood clustered the 18S rDNA sequences of both morphotypes with S. sparidarum, forming a well-supported clade within a sublineage that also includes Sphaerospora epinepheli (HQ871152) from an epinephelid, Sphaerospora formosa (FJ790308) from a gadid, and Sphaerospora olsoni (KJ526213) from an atherinid host.

Conclusions: Morphological and molecular analyses identify these myxosporeans as potential novel species within the Sphaerospora (sensu stricto) lineage. Their close phylogenetic relationship to S. sparidarum supports the hypothesis of host-driven diversification in this genus [1] and suggests that a hidden diversity of Sphaerospora species infecting sparids remains to be discovered. Their distant positioning from Sphaerospora sparis (JX286624) further strengthens the notion that the acquisition of sparids as intermediate hosts occurred independently at least twice during the evolutionary history of Sphaerospora.

[1] Patra et al., Parasit. Vectors 2018, 11: 347.

[2] Rocha et al., PeerJ. 2023, 11: e14599.

[3] Sirin et al., Parasitol. Res. 2018, 117, 2035-2041.

Funding: National funds through FCT (project PTDC_BIA-BMA_6363_2020).

1. ROCHA, SÓNIA, School of Medicine and Biomedical Sciences (ICBAS), University of Porto, Portugal, Presenter
2. ROCHA, SÓNIA, Institute for Research and Innovation in Health (i3S), University of Porto, Portugal, Presenter
3. SÁ, MÓNICA, School of Medicine and Biomedical Sciences (ICBAS), University of Porto, Portugal, Author
4. SÁ, MÓNICA, Institute for Research and Innovation in Health (i3S), University of Porto, Portugal, Author
5. RANGEL, LUÍS FILIPE, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Portugal, Author
6. RANGEL, LUÍS FILIPE, Faculty of Sciences (FCUP), University of Porto, Portugal, Author
7. SEVERINO, RICARDO, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Portugal, Author
8. SANTOS, MARIA JOÃO, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Portugal, Author
9. SANTOS, MARIA JOÃO, Faculty of Sciences (FCUP), University of Porto, Portugal, Author
10. RODRIGUES, PEDRO, School of Medicine and Biomedical Sciences (ICBAS), University of Porto, Portugal, Author
11. RODRIGUES, PEDRO, Institute for Research and Innovation in Health (i3S), University of Porto, Portugal, Author
12. CASAL, GRAÇA, School of Medicine and Biomedical Sciences (ICBAS), University of Porto, Portugal, Author
13. CASAL, GRAÇA, Associate Laboratory i4HB, Institute for Health and Bioeconomy, University Institute of Health Sciences – CESPU, Portugal, Author
14. CASAL, GRAÇA, UCIBIO, Toxicologic Pathology Research Laboratory, University Institute of Health Sciences (1H-TOXRUN, IUCS-CESPU), Portugal, Author

Survey of Kudoa spp. in Atlantic horse mackerel (Trachurus trachurus) in the Portuguese coast

Introduction:

Myxospores of Kudoa (Myxozoa: Multivalvulida) are frequently detected parasitizing the muscles of marine and estuarine fish worldwide, where occasionally whitish cysts are formed. These parasites have minimal effects on living fish but can cause tissue degradation after death, leading to myoliquefaction. This often results in the rejection of fishery products causing economic losses for commercial fisheries. Apart from that, some Kudoa spp. are now known to be zoonotic when fish is ingested raw. The present study aims to evaluate and characterize the presence of Kudoa spp. in Atlantic horse mackerel (Trachurus trachurus), a popularly consumed fish species in Portugal, one the highest seafood consumers in the world.

Methodology:

During the year of 2024, 197 samples (136 in winter and 81 in summer) of Atlantic horse mackerel were collected from four localities in mainland Portugal. The fish specimens were individually dissected and visually inspected for macroscopic cystic alterations. Two dorsal muscle samples were taken from each fish, one from the anterior and another from the posterior portion of the body. Tissue samples were individually macerated in saline solution (0.9% NaCl), filtered and observed under a light microscope for the detection of Kudoa myxospores.

Results:

Despite only one cyst was observed in one of the specimens of Atlantic horse mackerel during visual inspection, myxospores of Kudoa were detected in 95 to 100% of the fishery products analysed. When infected the fish would exhibit myxospores in both anatomical locations surveyed. On the next stage of the study, the molecular identification of the species involved will be determined.

Conclusions:

These preliminary results indicate a widespread dispersion of this parasitic genus in Atlantic horse mackerel from several localities in Portugal. This highlights the need for proper quality and sanitary checks in fishery products. More research is also required to clarify the life cycle and epidemiology of these parasites.

1. Gomes, Tiago, Faculty of Veterinary Medicine, Lusófona University; I-MVET; Veterinary and Animal Research Centre (CECAV), Presenter
2. Medeiros, Monalisa, Faculty of Veterinary Medicine, Lusófona University, Author
3. Abegão, Leonor, Faculty of Veterinary Medicine, Lusófona University, Author
4. Almeida, Laura, Faculty of Veterinary Medicine, Lusófona University, Author
5. Mendes, Beatriz, Faculty of Veterinary Medicine, Lusófona University, Author
6. Barbosa, Ricardo, Faculty of Veterinary Medicine, Lusófona University, Author
7. Moita, Tomás, Faculty of Veterinary Medicine, Lusófona University, Author
8. Mira, Inês, Faculty of Veterinary Medicine, Lusófona University; University of Évora, Author
9. Ramos, Sónia, Faculty of Veterinary Medicine, Lusófona University; I-MVET; Veterinary and Animal Research Centre (CECAV), Author
10. Munhoz, Ana, Faculty of Veterinary Medicine, Lusófona University; I-MVET; Veterinary and Animal Research Centre (CECAV), Author

Expansion of Proliferative Kidney Disease (PKD) in Rainbow Trout in Piedmont (Italy): Emerging Challenges for Regional Aquaculture

Proliferative kidney disease (PKD), caused by the myxozoan parasite Tetracapsuloides bryosalmonae, has never been found in Piedmont, west of the Ticino river, limiting its range to north-eastern Italy. This study resports the appareance  of PKD in rainbow trout (Oncorhynchus mykiss) farms across the region, with clinical manifestations peaking during warmer months when water temperatures exceed 15°C. The parasite’s life cycle involves freshwater bryozoans, such as Fredericella sultana, as intermediate hosts, facilitating its persistence and dissemination in aquatic environments.

In summer 2024, 50 rainbow trout from the same farm were brought to the ichthyopathology laboratory in Turin. All showed gill anaemia, cutaneous melanosis, apathetic behaviour, swollen abdomen and the kidney was severely hyperplasic. Molecular tests conducted on kidney and spleen samples of the subjects led to the diagnosis of PKD.

The expansion of PKD in Piedmont correlates with environmental factors, including rising water temperatures and the widespread presence of bryozoan populations in local water bodies. Infected fish exhibit clinical signs such as lethargy, darkened skin, abdominal distension, and gill anemia, leading to significant mortality rates that can reach up to 90% under favorable conditions for the parasite.

These outbreaks have substantial economic implications for the regional aquaculture industry, affecting fish health, farm productivity, and sustainability. Currently, there are no effective vaccines or treatments available for PKD, and control measures are limited. Management strategies focus on environmental monitoring, maintaining optimal water quality, and reducing stressors in fish populations to mitigate disease impact.

1. BONDAVALLI, FABIO, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Presenter
2. ESPOSITO, GIUSEPPE, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
3. PASTORINO, PAOLO, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
4. COLUSSI, SILVIA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
5. GINI, MARTINA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
6. MILANESE, GIULIA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
7. SCALA, SONIA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
8. BERGAMINO, CINZIA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
9. BOZZETTA, ELENA, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author
10. PREARO, MARINO, ISTITUTO ZOOPROFILATTICO SPERIMENTALE DEL PIEMONTE, LIGURIA E VALLE D’AOSTA, Author

Detecting the myxozoan parasite Tetracapsuloides bryosalmonae though highly invasive dreissenid mussels

Introduction
The Great Lakes watershed was recently invaded by Zebra (Dreissena polymorpha) and Quagga (D. bugensis) mussels. Reproducing and growing fast, they became widespread across large and small lakes and rivers in North America, altering ecosystems and threatening local freshwater fisheries. Dreissenid mussels may bio-accumulate substances and microorganisms that could become harmful for animals and people relying on impacted freshwater ecosystems. The myxozoan Tetracapsuloides bryosalmonae (Malacosporea) propagates through a two-host lifecycle and may cause Proliferative Kidney Disease (PKD) in salmonids. Infected freshwater bryozoans, moss filter-feeding organisms, release waterborne malacospores that can be infectious to susceptible salmonids. We recently confirmed the presence of T. bryosalmonae in several salmonid species and bryozoans across the Great Lakes region.
Methodology
Zebra and Quagga mussels were collected from rivers and lakes around Michigan, to assess whether they may be acting as vectors or paratenic hosts for T. bryosalmonae. Whole organisms and selected internal organs (e.g., gills, digestive glands) were screened for T. bryosalmonae detection by PCR, targeting the malacosporean 18S rDNA, followed by histological evaluation of relevant samples.
Results
Dreissenid mussels were often found sharing the same substrates with several bryozoan species, which also grow on their shells. Zebra mussels from distinct locations were found positive to T. bryosalmonae. At least in one instance, this kind of detection allowed the discovery of the parasite presence in a new lake in Michigan, from which no fish samples were available.Conclusions
Defining the possibility of detecting myxozoan parasites from highly invasive filter-feeder shellfish, which are much easier to collect than bryozoans, will determine if they could be used as bioindicators to help detect this regulatory fish pathogen. Defining how myxozoans interact with dreissenid mussels may provide further insights on how the parasite life cycle may be completed.

1. Ahmad Ali, Suhaylah, Fish Pathobiology and Immunology Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA, Author
2. Fusianto, Cahya K., Fish Pathobiology and Immunology Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA, Author
3. Buszkiewicz, John, Michigan Department of Natural Resources, Waterford, MI, USA, Author
4. GORGOGLIONE, BARTOLOMEO, Fish Pathobiology and Immunology Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA, Presenter

Phylogeny and histopathology of three Henneguya species parasitizing the Amazonian fish Cynodon gibbus

Introduction

Henneguya is a genus of endoparasitic myxozoans primarily known to infect freshwater fish. The Amazon Basin, one of the most biodiverse regions on Earth, harbors a vast array of fish species, many of which remain poorly studied from a parasitological perspective. Among this diverse ichthyofauna are members of the family Cynodontidae, which hold both economic and social importance due to their role in local fisheries and subsistence fishing. The present study reports three species of Henneguya infecting the gills of the cynodontid Cynodon gibbus, contributing to a broader understanding of parasite diversity in this ecosystem.

Methodology

Twelve specimens of C. gibbus were collected from the Capim River, in the municipality of Ipixuna do Pará, State of Pará, Brazil, in January 2024, in collaboration with local fishermen. The fish were examined for myxosporean infections, and the parasites found were analyzed using morphological, molecular, and histological techniques. DNA was extracted from the spores, and the small subunit ribosomal DNA (SSU rDNA) was sequenced using Oxford Nanopore Technologies. Phylogenetic analyses were performed using the Maximum Likelihood method.

Results

Plasmodia containing three distinct Henneguya myxospore morphotypes were identified: basifilamental, intrafilamental, and intralamellar. The respective measurements obtained were as follows: total myxospore lengths of 36 µm, 38 µm, and 37 µm; myxospore body lengths of 12 µm, 9.8 µm, and 10 µm; myxospore widths of 3.6 µm, 3.9 µm, and 3.8 µm; and caudal appendage lengths of 24 µm, 28 µm, and 27 µm. Nematocysts of similar size measured 5.1 × 1.4 µm, 4.0 × 1.5 µm, and 4.0 × 1.0 µm. All species showed 3–4 tubule coils. Histological analysis revealed that the intrafilamental-type parasite developed in the connective tissue near blood vessels, causing compression of adjacent tissues. The intralamellar type developed in the epithelial region, leading to deformation of the lamellar structure. SSU rDNA analysis confirmed that these morphotypes represent three previously undescribed Henneguya species. Phylogenetic analysis indicated that the basifilamental and intrafilamental types are sister species, suggesting a recent speciation event. The intralamellar morphotype was identified as a sister species to Henneguya tietensis, previously described from Prochilodus lineatus.

Conclusion

This study reports three previously undescribed species of Henneguya infecting C. gibbus, representing the first record of Myxozoa in this host species. These findings highlight the high, yet understudied, parasite diversity of the Amazon Basin.

Funded by São Paulo Research Foundation – FAPESP (Thematic Project #2018/24980-8;Doctoral Fellowship #2023/06420-3.

1. FIGUEREDO, RAYLINE T. A., UNICAMP, Presenter
2. LONG, PAUL F., King’s College London, Author
3. ADRIANO, EDSON A., UNIFESP, Author

Infection of the gibel carp (Carassius auratus gibelio Berg, 1932) with myxozoan parasites in a pond farm of Hungary

Introduction: Gibel carp is a native and economically important freshwater species in China, but is considered a highly invasive species in Europe, where its wide-range habitat use threatens native fish populations, such as the crucian carp. Nowadays, gibel carp can be found in most European waters and fish farms. While over 40 myxozoan parasites have been reported from gibel carp in China, only two myxozoan species have been reported in Hungary. Due to its invasive nature and limited economic importance in Hungary, parasitological studies on this fish species have often been overlooked. Given the limited number of myxosporean species documented from gibel carp in Hungary, a comprehensive survey was conducted on this species.

Methodology: Between November 2023 and June 2024, ninety-four gibel carp were caught by gillnet from earth ponds at a fish farm in Ócsárd near Pécs, Hungary. The fish were dissected, and all organs were thoroughly examined for myxozoan infections under stereo and light microscopes. Spores were photographed under a light microscope and measured following the guidelines of Lom and Arthur (1989). For molecular analysis, 18S rDNA gene of the myxospores was amplified in direct or nested PCR reactions with various primer combinations. Phylogenetic trees were constructed using both Maximum Likelihood (ML) in MEGA X and Bayesian Inference (BI) in MrBayes 3.2.4.

Results: This study reports on six myxozoan parasites, including three different Myxobolus spp., one Thelohanellus sp., one Sphaerospora sp., and one Zschokkella sp. infecting various organs and tissues. Based on the morphological and molecular data, we described four new species: Myxobolus ocsardiensis n. sp., found in the kidney and liver; Myxobolus pecsensis n. sp., found in the gill cartilage; Thelohanellus imrei n. sp. found in the connective tissues of the gill arch and pharynx; and Zschokkella chezhachei n. sp. found in the bile duct. Additionally, we identified spores resembling those of Myxobolus diversus, a parasite of goldfish fins, and Sphaerospora molnari known from the gills of crucian carp and common carp. The original description of these species lacked several important information, such as spore measurements and molecular data, required for the redescription.

Conclusion: We describe four new species, proposing the names Myxobolus ocsardiensis n. sp., Myxobolus pecsensis n. sp., Thelohanellus imrei n. sp., and Zschokkella chezhachei n. sp., and redescribe M. diversus and S. molnari, with their first report in gibel carp.

1. Suhaimi, Nadhirah Syafiqah, HUN-REN Veterinary Research Institute, Presenter
2. Cech, Gábor, HUN-REN Veterinary Research Institute, Author
3. Molnár, Kálmán, HUN-REN Veterinary Research Institute, Author
4. Székely, Csaba, HUN-REN Veterinary Research Institute, Author
5. Sellyei, Boglárka, HUN-REN Veterinary Research Institute, Author

Occurrence of Kudoa sp. induced post-mortem myoliquefaction in Atlantic mackerel (Scomber scombrus) landed in Ireland

Atlantic mackerel (Scomber scombrus) is Ireland’s most valuable wild-caught fish species. In recent years, Irish pelagic processors have noted an increase in the occurrence of post-mortem myoliquefaction, most commonly known as ‘soft flesh’ or ‘jelly flesh’. Studies from across the Northeast Atlantic on Atlantic mackerel have linked post-mortem myoliquefaction to a myxosporean parasite called Kudoa thyrsites, which is known to infect many freshwater and marine fish species. Despite mackerel’s economic importance, the number of incidents remain largely unknown in Ireland, and the causative agent has not previously been confirmed. Here, we examined Kudoa in Atlantic mackerel displaying post-mortem myoliquefaction and assessed the occurrence of ‘jelly flesh’. We confirmed the presence of K. thyrsites in the muscle tissue of affected mackerel collected from a major fishing port in the northwest of Ireland (Killybegs). Our K. thyrsites isolate matched the identity of previous isolates obtained from Atlantic mackerel in Scotland and Norway. During the 2024/2025 fishing season, the occurrence of ‘jelly flesh’ in commercial-sized mackerel was recorded as part of the quality control procedure at an Irish fish processing facility and was found to be low. Myoliquefaction was detected in only 0.5% of individuals (n=55/18610), with the majority of affected fish falling within the economically important size range of 300-500g. The findings build upon our understanding of K. thyrsites in Atlantic mackerel and highlight the need for long-term monitoring to elucidate sources of infection, routes of transmission, and temporal and spatial trends in the occurrence of the parasite. Ultimately, developing a robust comprehension of K. thyrsites infection is essential to assess its impact on the pelagic fishing industry in the wider Northeast Atlantic region.

1. Kiralyova, Viktoria, Marine and Freshwater Research Centre, Atlantic Technological University (ATU), Galway, Ireland, Presenter
2. Brophy, Deirdre, Marine and Freshwater Research Centre, Atlantic Technological University (ATU), Galway, Ireland, Author
3. O’Dwyer, Katie, Marine and Freshwater Research Centre, Atlantic Technological University (ATU), Galway, Ireland, Author
4. Talbot, Anita, Marine and Freshwater Research Centre, Atlantic Technological University (ATU), Galway, Ireland, Author
5. Gallagher, Michael, Bord Iascaigh Mhara (BIM), Killybegs Fisheries Harbour Centre, Killybegs, Ireland, Author
6. Giulietti, Lucilla, Institute of Marine Research (IMR), Nordnes, Bergen, Norway, Author

Morphological, molecular, and Phylogenetic characterization of the first African species of Hennegoides (Myxozoa : Myxobolidae) parasite of Citharinus gibbosus from Kadey River in Cameroon

Introduction Citharinus gibbosus belongs to the family Citharinidae, one of the endemic fish families of African freshwaters. Little is known about its myxozoan diversity despite its distribution in several rivers across the continent. Methodology Morphological and molecular screening of myxospores was performed on 10 specimens of C. gibbosus collected from the Kadey River, a tributary of the Sangha River in the Congo Basin in Cameroon. Phylogenetic analysis was performed using maximum likelihood and Bayesian inference methods. Results Myxozoan infection was detected in the gills of 60% of the fish and the infection was characterized as intrafilamental-epithelial type. The cysts were filled with myxospores of Hennegoides africanus sp. nov. The myxospore body was vaulted from one side, with a narrow end, and measured 13.5 (12.4 – 14.8) x 2.1 (1.9 – 2.5) µm. The caudal appendages were divided into two segments; the thick segment was 7.2 (5.6-8.9) µm long while the filamentous segment was 31.3 (25.4-34.93) µm long. The two polar capsules were elongated, different in size, and had different positions in the myxospore body. The smaller polar capsule is close to the anterior end of the myxospore and measures 2.8 (2.18-3.54) x 0.9 (0.7-1.1) µm, while the larger capsule located posterior to the smaller one, measures 3.8 (3.21-4.45) x 1.4 (1.2-1.7) μm. A BLAST search revealed that the newly obtained 18 rDNA sequence had a low sequence similarity to sequences available in GenBank. Phylogenetic analysis of the SSU rRNA gene placed the new species with two undetermined species of Henneguya and Myxobolus, which infect the gills of African characiformes fishes. Conclusion This study reports for the first time the genus Hennegoides outside Asia, America and India.

1. Onana Ateba, Nelly Ornelle, UNIVERSITY OF YAOUNDE I, Presenter
2. Lekeufack Folefack, Guy Benoît, UNIVERSITY OF YAOUNDE I, Author
3. Fadanka Wapouo, Stephane, International Center for Genetic Engineering and Biotechnology, Author
4. Berinyuy Tata, Gloria, MboaLab Biotech, Author

The local transcriptomic response of Atlantic salmon skin to salmon louse chalimi and adults

Introduction:

Salmon lice (Lepeophtheirus salmonis) parasitize the skin of salmonids and pose a significant problem to salmonid aquaculture. Unlike resistant salmonids, the immune response of Atlantic salmon does not efficiently clear any of the various salmon louse life stages, probably due to immuno-modulation of the host by the lice, for example by secretes from the labial glands. A better understanding of the molecular reactions of salmon skin in contact with lice can help to explain this host-parasite interaction. Previous studies have focused on a few pre-selected genes, whereas a few holistic studies have only looked at few life stages. Here, we aimed to analyze the transcriptomic response of Atlantic salmon to chalimus and adult lice.

Methodology:

RNA-Seq data was used to analyze the gene expression directly at the attachment site of chalimus and adult lice. Reads were mapped to the transcriptome using the Salmon tool and differentially expressed genes (DEGs) were identified with DeSeq2. In a follow-up experiment, salmon were co-infested with chalimi and adult lice and samples were taken from both unaffected and infested areas. While one sample per fish was taken underneath adult lice, five samples were collected under chalimi. Moreover, to standardize the analyzed skin area size, a subsample was punched out from each chalimus sample including the lice. Gene expression of immune-related genes in addition to salmon louse labial gland genes was measured using qPCR.

Results:

RNA-Seq analysis revealed a highly localized cutaneous response to chalimi and adult lice. The gene expression in samples from infested fish taken from non-attachment sites resembled that of non-infested fish. At the attachment sites, however, many genes were differentially expressed, with a substantial overlap between DEGs seen under both stages. Still, there were stage-specific DEGs, especially under adult lice. The data also indicated a higher influx of macrophages and neutrophils to the attachment site of adult lice than to that of chalimi. The qPCR results revealed that the skin reaction to chalimi is mostly limited to a very small region close to the lice, where the expression of salmon immune genes was independent of the expression of louse labial gland genes The co-infestation experiment confirms, however, that skin inflammation is stronger towards the adult lice stage.

Conclusions:

The results shed light on the molecular responses of salmon skin to two different lice stages, contributing knowledge that might aid in the development of immuno-based treatment and preventative options against salmon lice.

1. Borchel, Andreas, University of Bergen, Presenter
2. Midtbø, Helena Marie Doherty, University of Bergen, Author
3. Øvergård, Aina-Cathrine, University of Bergen, Author