Phylogenetic position of Ancyrocephalus (sensu lato) curtus Achmerov, 1952 (Monopisthocotylea, Dactylogyridae), a parasite of fish Perccottus glenii Dybowski, 1877(Gobiiformes: Odontobutidae).

The genus Ancyrocephalus sensu lato is a large assemblage of species of dactylogyrid monopisthocotyleans without clear taxonomic boundaries. Despite an urgent need for revision, only three representatives of this taxon have been molecularly characterised so far. We found specimens of Ancyrocephalus curtus, a previously non-genotyped species, in gills of Perccottus glenii caught in the River Syumnyur, Amur Basin, Russia. The aim of this study was to assess the phylogenetic position of this parasite using partial sequences of 28S rRNA gene. In the phylogenetic tree, A. curtus appeared as a sister taxon to the dactylogyrine genus Gobioecetes. The new molecular evidence supports the hypothesis about the non-monophyletic status of Ancyrocephalus sensu lato.

Integrative Taxonomy of Urocleidoides spp. (Monogenoidea, Dactylogyridae) Parasites of Pseudanos trimaculatus (Characiformes: Anostomidae) from Eastern Amazon, Brazil.

Two new species of Urocleidoides are described from the gills of Pseudanos trimaculatus (Characiformes: Anostomidae) from the coastal drainages of the Eastern Amazon, Brazil. Urocleidoides itabocaensis n. sp. is characterized by having a sclerotized, tubular, sigmoid male copulatory organ (MCO), a circular sclerotized tandem brim associated with the base of the MCO; an accessory piece articulated with the MCO, a V-shaped, divided into two subunits, distal subunit spoon-shaped; and a vaginal pore dextroventral with opening marginal. Urocleidoides omphalocleithrum n. sp. is characterized by presenting a C-shaped or sigmoid MCO; an accessory piece articulated with the MCO, L-shaped, divided into two subunits, distal subunit gutter-shaped; a vaginal pore dextroventral with opening marginal; and a ventral bar broadly V-shaped, with anteromedial projection. Molecular phylogenetic analysis based on partial 28S rDNA and COI mtDNA genes indicate that U. itabocaensis n. sp. and U. omphalocleithrum n. sp. are closely related and appear as a sister group to other Urocleidoides species (U. paradoxus, U. digitabulum and U. sinus) parasitizing anostomid fishes. This study represents the first record of monogenoids from the gills of P. trimaculatus for the Eastern Amazon.

Parasites (Monogenea) of tilapias Oreochromis niloticus and Coptodon rendalli (Cichlidae) in a river spring in Brazil.

In the present study, we examined 30 individuals of introduced African cichlids, Oreochromis niloticus and Coptodon rendalli, collected in a river spring of the Pardo River, Paranapanema River basin, southeastern Brazil. Based on morphological and molecular analyses of the partial LSU rDNA gene, we identified four species of monogeneans, Cichlidogyrus tilapiae, C. thurstonae, C. mbirizei, and Scutogyrus longicornis on the gills of O. niloticus, whereas individuals of C. rendalli were infested only with C. papernastrema. This is the first record of C. mbirizei and C. papernastrema in tilapias from Brazil. The ecological consequences of the introduction of exotic species of tilapia such as O. niloticus and C. rendalli along with their monogenean parasites in a wild environment represented by a river spring are discussed. Our new molecular data on Cichlidogyrus and Scutogyrus contribute to the investigation of the phylogenetic interrelationships of these widely distributed genera of monogeneans since their species composition is still unsettled.

Title: Parasites (Monogenea) des tilapias Oreochromis niloticus et Coptodon rendalli (Cichlidae) dans une source au Brésil. Abstract: Dans la présente étude, nous avons examiné 30 individus de cichlidés africains introduits, Oreochromis niloticus et Coptodon rendalli, collectés dans une source fluviale du fleuve Pardo, bassin du fleuve Paranapanema, dans le sud-est du Brésil. Sur la base d'analyses morphologiques et moléculaires du gène partiel de l'ADNr LSU, nous avons identifié quatre espèces de monogènes, Cichlidogyrus tilapiae, C. thurstonae, C. mbirizei et Scutogyrus longicornis sur les branchies d'O. niloticus, alors que les individus de C. rendalli étaient infestés uniquement par C. papernastrema. Il s'agit du premier signalement de C. mbirizei et C. papernastrema chez des tilapias du Brésil. Les conséquences écologiques de l'introduction d'espèces exotiques de tilapia telles que O. niloticus et C. rendalli ainsi que leurs monogènes parasites dans un environnement sauvage représenté par une source fluviale sont discutées. Nos nouvelles données moléculaires sur Cichlidogyrus et Scutogyrus contribuent à l'étude des interrelations phylogénétiques de ces genres de monogènes largement distribués puisque leur composition spécifique est encore incertaine.

Two new Neotetraonchus species (Dactylogyridea, Dactylogyridae) parasitising the Peruvian sea catfish Galeichthys peruvianus (Siluriformes, Ariidae), including molecular data.

As part of a parasitological survey, several specimens of two new monopisthocotylean species, Neotetraonchus celsomanueli sp. nov. and N.peruvianus sp. nov. (Dactylogyridea, Dactylogyridae), were collected from the gill filaments of the Peruvian sea catfish Galeichthys peruvianus (Siluriformes, Ariidae) off Puerto Pizarro, Tumbes region, Peru. Neotetraonchus celsomanueli sp. nov. is characterised by an MCO with a T-shaped distal end and an accessory piece that is ribbed and expanded proximally with a worm-shaped termination. Neotetraonchus peruvianus sp. nov. is typified by its MCO, which has a sledgehammer-shaped distal end and an accessory piece with a claw-shaped distal end. Additionally, N.peruvianus sp. nov. is characterised by its jellyfish-shaped onchium. A partial 28S rDNA sequence was obtained from N.celsomanueli sp. nov., and a phylogenetic analysis was conducted. This analysis revealed the phylogenetic position of Neotetraonchus celsomanueli sp. nov. within a clade comprising monopisthocotylean parasites of diadromous and marine ariid catfishes, including Hamatopeduncularia spp., Chauhanellus spp., Thysanotohaptor Kritsky, Shameem, Kumari & Krishnaveni, , and Neocalceostomoides spinivaginalis Lim, 1995. This finding brings the number of known Neotetraonchus species to seven and represents the first described Neotetraonchus species infecting marine catfishes from Peru.

Identification of a new gregarine parasite associated with mass mortality events of freshwater pearl mussels (Margaritifera margaritifera) in Sweden.

Freshwater bivalves play key ecological roles in lakes and rivers, largely contributing to healthy ecosystems. The freshwater pearl mussel, Margaritifera margaritifera, is found in Europe and on the East coast of North America. Once common in oxygenated streams, M. margaritifera is rapidly declining and consequently assessed as a threatened species worldwide. Deterioration of water quality has been considered the main factor for the mass mortality events affecting this species. Yet, the role of parasitic infections has not been investigated. Here, we report the discovery of three novel protist lineages found in Swedish populations of M. margaritifera belonging to one of the terrestrial groups of gregarines (Eugregarinorida, Apicomplexa). These lineages are closely related-but clearly separated-from the tadpole parasite Nematopsis temporariae. In one lineage, which is specifically associated with mortality events of M. margaritifera, we found cysts containing single vermiform zoites in the gills and other organs of diseased individuals using microscopy and in situ hybridization. This represents the first report of a parasitic infection in M. margaritifera that may be linked to the decline of this mussel species. We propose a tentative life cycle with the distribution of different developmental stages and potential exit from the host into the environment.

DNA Methylation Analysis Reveals Potential Mechanism in Takifugu rubripes Against Cryptocaryon irritans Infection.

Takifugu rubripes (T. rubripes) is a valuable commercial fish, and Cryptocaryon irritans (C. irritans) has a significant impact on its aquaculture productivity. DNA methylation is one of the earliest discovered ways of gene epigenetic modification and also an important form of modification, as well as an essential type of alteration that regulates gene expression, including immune response. To further explore the anti-infection mechanism of T. rubripes in inhibiting this disease, we determined genome-wide DNA methylation profiles in the gill of T. rubripes using whole-genome bisulfite sequencing (WGBS) and combined with RNA sequence (RNA-seq). A total of 4659 differentially methylated genes (DMGs) in the gene body and 1546 DMGs in the promoter between the infection and control group were identified. And we identified 2501 differentially expressed genes (DEGs), including 1100 upregulated and 1401 downregulated genes. After enrichment analysis, we identified DMGs and DEGs of immune-related pathways including MAPK, Wnt, ErbB, and VEGF signaling pathways, as well as node genes prkcb, myca, tp53, and map2k2a. Based on the RNA-Seq results, we plotted a network graph to demonstrate the relationship between immune pathways and functional related genes, in addition to gene methylation and expression levels. At the same time, we predicted the CpG island and transcription factor of four immune-related key genes prkcb and mapped the gene structure. These unique discoveries could be helpful in the understanding of C. irritans pathogenesis, and the candidate genes screened may serve as optimum methylation-based biomarkers that can be utilized for the correct diagnosis and therapy T. rubripes in the development of the ability to resist C. irritans infection.

Description of two new species of dactylogirids (Monogenoidea: Dactylogyridae) from Mylossoma albiscopum (Cope, 1872) (Characiformes: Serrasalmidae) from the Peruvian Amazonia.

INTRODUCTION: Two new dactylogyrid monogeneans, Anacanthorus cultro n. sp. and Notozothecium palometae n. sp., are described based on specimens collected from the gill filaments of Mylossoma albiscopum (Cope, 1872) (Characiformes: Serrasalmidae), a pelagic and herbivore teleost collected in the Tigre river, Loreto, Peru. MATERIALS AND METHODS: Some monogeneans were stained with Gomori's trichrome and mounted in Canada Balsam to determine internal soft structures. Others were cleared in Hoyer's medium for the study of sclerotized structures. Drawings were made using a drawing tube and a microprojector. RESULTS: Anacanthorus cultro n. sp. is characterized by the presence of a rod-shaped male copulatory organ (MCO) lacking featherlike structures, and a knife-shaped accessory piece with a submedial knob. Notozothecium palometae n. sp. can be distinguished from all congeners by its MCO with a subbasal spur and an accessory piece with inverted hammer shaped. CONCLUSIONS: This is the first data on the parasites of M. albiscopum, a popular fish in local markets. Anacanthorus cultro n. sp. is the twenty-fifth documented species of the genus in Peru, while N. palometae n. sp. represents the seventh species of the genus known to infect freshwater fish species in Peru.

Identification of new amoebae strains in rainbow trout (Oncorhynchus mykiss, Walbaum) farms affected by nodular gill disease (NGD) in Northeastern Italy.

Nodular gill disease (NGD) is an emerging condition associated with amoeba trophozoites in freshwater salmonid farms. However, unambiguous identification of the pathogens still must be achieved. This study aimed to identify the amoeba species involved in periodic NGD outbreaks in two rainbow trout (Oncorhynchus mykiss) farms in Northeastern Italy. During four episodes (February-April 2023), 88 fish were euthanized, and their gills were evaluated by macroscopic, microscopic and histopathological examination. The macroscopic and microscopic severity of the lesions and the degree of amoebae infestation were scored and statistically evaluated. One gill arch from each animal was put on non-nutrient agar (NNA) Petri dishes for amoeba isolation, cultivation and subsequent identification with SSU rDNA sequencing. Histopathology confirmed moderate to severe lesions consistent with NGD and mild to moderate amoeba infestation. The presence of amoebae was significantly correlated with lesion severity. Light microscopy of cultured amoebae strains and SSU rDNA analysis revealed the presence of a previously characterized amoeba Naegleria sp. strain GERK and several new strains: two strains from Hartmannelidae, three vannelid amoebae from the genus Ripella and cercozoan amoeba Rosculus. Despite the uncertainty in NGD etiopathogenesis and amoebae pathogenic role, identifying known and new amoebae leans towards a possible multi-aetiological origin.

Establishment of a gill cell line from yellowfin seabream (Acanthopagrus latus) for studying Amyloodinium ocellatum infection of fish.

Amyloodinium ocellatum is among the most devastating protozoan parasites, causing huge economic losses in the mariculture industry. However, the pathogenesis of amyloodiniosis remains unknown, hindering the development of targeted anti-parasitic drugs. The A. ocellatum in vitro model is an indispensable tool for investigating the pathogenic mechanism of amyloodiniosis at the cellular and molecular levels. The present work developed a new cell line, ALG, from the gill of yellowfin seabream (Acanthopagrus latus). The cell line was routinely cultured at 28°C in Dulbecco's modified Eagle medium (DMEM) supplemented with 15% fetal bovine serum (FBS). ALG cells were adherent and exhibited an epithelioid morphology; the cells were stably passed over 30 generations and successfully cryopreserved. The cell line derived from A. latus was identified based on partial sequence amplification and sequencing of cytochrome B (Cyt b). The ALG was seeded onto transwell inserts and found to be a platform for in vitro infection of A. ocellatum, with a 37.23 ± 5.75% infection rate. Furthermore, scanning electron microscopy (SEM) revealed that A. ocellatum parasitizes cell monolayers via rhizoids. A. ocellatum infection increased the expression of apoptosis and inflammation-related genes, including caspase 3 (Casp 3), interleukin 1 (IL-1), interleukin 10 (IL-10), tumour necrosis factor-alpha (TNF-α), in vivo or in vitro. These results demonstrated that the in vitro gill cell monolayer successfully recapitulated in vivo A. latus host responses to A. ocellatum infection. The ALG cell line holds great promise as a valuable tool for investigating parasite-host interactions in vitro.

A new species of Urocleidoides Mizelle & Price 1964 (Monogenea: Dactylogyridae) parasite of Hemiodus orthonops Eigenmann & Kennedy, 1903 (Hemiodontidae) from the upper Paraná River floodplain.

During the study of ectoparasites (Platyhelminthes) of fish in the floodplain of the Upper Paraná River - Brazil, a new species of Urocleidoides, present in the gill filaments of Hemiodus orthonops (Hemiodontidae), is described using morphological description and molecular data from the mitochondrial region of cytochrome c oxidase, subunit 1 (COI) and the partial region of the 28S rDNA gene. Urocleidoides luquei n. sp. differs from all its congeners by the presence of a filament that joins the accessory piece to the base of the male copulatory organ and resembles U. paradoxus and U. surianoae. Phylogenetic analyses using molecular data revealed that U. luquei n. sp. forms a paraphyletic group concerning the other Urocleidoides species. In this way, as well as contributing to the description of a new species, we seek to encourage and contribute to the increase in research using integrative taxonomy, thus making it possible to elucidate some unresolved questions about the genus Urocleidoides.

Essential oil of Piper hispidum (Piperaceae) has efficacy against monogeneans, and effects on hematology and gill histology of Colossoma macropomum.

This study investigated for the first time the effectiveness of therapeutic baths with essential oil (EO) of Piper hispidum against monogeneans Anacanthorus spathulatus, Notozothecium janauachensis, Mymarothecium boegeri and Linguadactyloides brinkmanni from the gills of Colossoma macropomum, as well as the hematological and histological effects on this fish. In therapeutic baths, 100 mg/L of P. hispidum essential oil and two control groups (water from the culture tank and water from the culture tank with 70% alcohol) were exposed for 1 h/day, with intervals of 48 hours for 3 days, and three replicates each were used. Therapeutic baths with 100 mg/L of P. hispidum essential oil had an efficacy of 78.6% against monogeneans. The toxicity of this essential oil was low, since there were a few physiological and histopathological changes that did not compromise the functioning of the gills of the fish. Therefore, 100 mg/L of P. hispidum essential oil was effective for controlling monogeneans in C. macropomum, when short therapeutic baths were used without compromising the health of the exposed fish.

New species of Demidospermus (Monogenoidea: Dactylogyridae) from the gills of Pseudoplatystoma punctifer (Siluriformes: Pimelodidae) collected in the Peruvian Amazonia.

Pseudoplatystoma punctifer is a catfish species that occupies the first place in the statistics of fishing landings in the region of Loreto, being of economic importance in the Peruvian Amazonia. As an initiative to know the parasites present in the gills of P. punctifer from the Peruvian Amazonia, a study was carried out with fish collected in the Belén Market, in Loreto-Peru. Specimens were provided between June and October 2018 from local fishermen from the Belén Market, in Loreto-Peru and samples were processed and analyzed in the "Laboratorio de Parasitología y Sanidad Acuícola" from the "Instituto de Investigaciones de la Amazonía Peruana" (IIAP) in Iquitos, Loreto-Peru. The analyzes of the gills revealed the presence of two new species of Monogenoidea: Demidospermus aureagarciae n. sp. and D. doncellae n. sp. These species are unique among congeners by the morphology of the copulatory complex and vagina. Demidospermus aureagarciae n. sp presents a male copulatory organ as a coiled tube, with a complete counterclockwise ring, with dilated base with a developed sclerotized margin, from which a flap projects; a concave accessory piece, with a tapered and curved distal part and a saculiform vaginal vestibule, connected to the vaginal canal. Demidospermus doncellae n. sp. presents a copulatory complex that is an elongated coiled tube, with approximately three clockwise rings, with dilated base with a developed sclerotized margin, from which a flap projects; an accessory piece sheath like, and a sclerotized vagina with dextral position, with saclike vaginal vestibule, connected to an elongated canal.

Species-specific in situ hybridization confirms arrested development of Henneguya ictaluri in hybrid catfish (Channel Catfish × Blue Catfish) under experimental conditions, with notes on mixed-species infections in clinical cases of proliferative gill disease from Mississippi catfish aquaculture.

OBJECTIVE: Proliferative gill disease (PGD) in Channel Catfish Ictalurus punctatus and hybrid catfish (Channel Catfish × Blue Catfish I. furcatus) is attributed to the myxozoan Henneguya ictaluri. Despite evidence of decreased H. ictaluri transmission and impaired parasite development in hybrid catfish, PGD still occurs in hybrid production systems. Previous metagenomic assessments of clinical PGD cases revealed numerous myxozoans within affected gill tissues in addition to H. ictaluri. The objective of this study was to investigate the development and pathologic contributions of H. ictaluri and other myxozoans in naturally and experimentally induced PGD. METHODS: Henneguya species-specific in situ hybridization (ISH) assays were developed using RNAscope technology. Natural infections were sourced from diagnostic case submissions in 2019. Experimental challenges involved Channel Catfish and hybrid catfish exposed to pond water from an active PGD outbreak, and the fish were sampled at 1, 7, 10, 12, 14, 16, 18, and 20 weeks postchallenge. RESULT: Nine unique ISH probes were designed, targeting a diagnostic variable region of the 18S ribosomal RNA gene of select myxozoan taxa identified in clinical PGD cases. Partial validation from pure H. ictaluri, H. adiposa, H. postexilis, and H. exilis infections illustrated species-specific labeling and no cross-reactivity between different myxozoan species or the catfish hosts. After experimental challenge, mature plasmodia of H. ictaluri and H. postexilis formed in Channel Catfish but were not observed in hybrids, suggesting impaired or delayed sporogenesis in the hybridized host. These investigations also confirmed the presence of mixed infections in clinical PGD cases. CONCLUSION: Although H. ictaluri appears to be the primary cause of PGD, presporogonic stages of other myxozoans were also present, which may contribute to disease pathology and exacerbate respiratory compromise by further altering normal gill morphology. This work provides molecular confirmation and more resolute developmental timelines of H. ictaluri and H. postexilis in Channel Catfish and supports previous research indicating impaired or precluded H. ictaluri sporogony in hybrid catfish.

Unraveling the host-parasite interaction: immune response in Oreochromis mossambicus to Cymothoa eremita (Isopoda, Cymothoidae) infection.

The host immune response in Oreochromis mossambicus during natural infection with the isopod Cymothoa eremita was investigated. The naturally infected fishes were examined for enzyme profile, viz., respiratory burst activity (RBA), myeloperoxidase activity (MPO), and expression of immune-related genes, viz., toll-like receptor 22 (TLR 22), interleukin-1ß (IL-1ß), tumor necrosis factor α (TNF-α), complement component (C3), chemokine (CXCa), and ß-actin in tissues of various organs (buccal cavity, gills and anterior kidney). Significant reduction (P < 0.05) in RBA and MPO was observed in the parasite-infected fishes when compared to the uninfected control fishes. In the buccal cavity, the expression of the immune-related genes was significantly (P < 0.05) upregulated, whereas all the genes except IL-1ß were significantly (P < 0.05) upregulated in the anterior kidney. In the case of gill tissue, the expressed genes showed a varied type of regulation. The immunological responses in O. mossambicus during isopod infection have not been investigated in detail so far, and this is the first study unveiling such insights. Hence, this study will help to improve our molecular understanding of the host-immune response to parasitic isopod infection.

Live Freshwater Parasite, Salmincola californiensis (Copepoda: Lernaeopodidae), on the Gills of an Ocean-Migrating Steelhead Trout (Oncorhynchus mykiss) and Discussion on the Origin and Survival of the Parasite at Sea.

Salmincola californiensis is a parasitic copepod of freshwater salmonids in the North Pacific rim countries. Sixteen adult females of the species were found alive on the gills of an ocean-age 4, maturing steelhead trout, Oncorhynchus mykiss, caught in offshore waters (50°30'N, 179°30'W) of the North Pacific Ocean in July 1997. This is the first evidence of live individuals of S. californiensis from ocean-migrating salmonids. When found, copepods were attached to the distal ends of gill filaments, and their bodies were observed to be slowly moving in Petri dishes with seawater. Ocean-migrating steelhead trout comprise individuals originating from western Kamchatka (Russia) and western North America. Based on the date and catch location of the infected fish, it is inferred that it originated from western North America, where it acquired S. californiensis infection in fresh water. As this fish spent about 4 years in the ocean, the copepods likely survived the same period at sea. However, if the fish was a kelt, the survival period of the copepods in the ocean may be shorter than four years. To confirm identification of the copepods, adult females of S. californiensis are briefly described using the specimens collected from the fish.

Description of a new species, Pseudodiscocotyla mikiae n. sp. (Monogenea: Discocotylidae) parasitic on gills of Pristipomoides filamentosus from off Okinawa-jima island in Japan, with redescription of Pseudodiscocotyla opakapaka.

Two species of Pseudodiscocotyla Yamaguti, 1965 (Monogenea: Discocotylidae) were collected from crimson jobfish Pristipomoides filamentosus (Valenciennes) (Perciformes: Lutjanidae) off Okinawa-jima island, southern Japan. Pseudodiscocotyla opakapaka is redescribed and represents the first Japanese record. A new species, Pseudodiscocotyla mikiae n. sp., differs from Ps. opakapaka in the absence of spines around the male genital pore, the shape of the vaginal pore, the presence of spines inside the vaginal pore, and the shape of the clamp. The locations of the male genital atrium and the vaginal pore in both species were similar, and the observed armament differences of the male copulatory organ are therefore presumed to establish reproductive isolation. The phylogenetic trees for the Mazocraeidea based on the partial 28S rDNA sequences were created using new sequences of Pseudodiscocotyla mikiae n. sp., and Discocotylidae formed a sister group with the species Diclidophoridae, Macrovalvitrematidae, and Plectanocotylidae. Pristipomoides filamentosus is widely distributed across the Indo-Pacific, and Pseudodiscocotyla mikiae n. sp. could share the distribution of the host.

Morphological, histopathological, ultrastructural and phylogenetic analysis of Henneguya archosargus n. sp. (Cnidaria, Myxosporea) infecting the sparid fish Archosargus probatocephalus in Brazilian waters.

The introduction of new fish species to the aquaculture industry is essential to halt the progressive decline of natural fish stocks. The sheepshead Archosargus probatocephalus is a commercially valuable sparid fish with potential for breeding in captivity, but with limited information regarding parasitic infections that could pose a significant threat for its sustainable production. Thus, the present study aimed to study the myxozoan diversity infecting A. probatocephalus. A novel Henneguya sp. was detected forming plasmodia in the gill lamellae of specimens inhabiting the Brazilian coast, and is characterized based on morphological, histopathological, ultrastructural, molecular, and phylogenetic data. Myxospore total length was 21.3 ± 0.8 µm, with myxospore body 10.0 ± 0.5 µm long, 6.2 ± 0.3 µm wide, and 4.8 ± 0.5 µm thick. Caudal appendages were 10.3 ± 0.5 µm long and did not present any type of coating. Two pyriform polar capsules, 3.4 ± 0.3 µm long and 1.5 ± 0.2 µm wide, each containing an isofilar polar tubule with 4-5 coils. Histopathological analyses showed large intralamellar polysporic plasmodia associated with vascular congestion of the gill filament and gill lamellae, as well as epithelial hyperplasia causing partial or total fusion of gill lamellae. Maximum likelihood and Baysesian inference SSU rDNA-based phylogenetic analyses showed the novel sequence grouped within the marine clade of Henneguya spp. that mostly parasitize fishes belonging to Eupercaria incertae sedis.

l-fucoside localization in the gills of the genus Takifugu and its possible implication in the parasitism of Heterobothrium okamotoi (Monogenea: Diclidophoridae).

BACKGROUND: The monogenean parasite Heterobothrium okamotoi only parasitizes the gills of Takifugu rubripes. In this study, we hypothesized that the carbohydrates contribute to high host specificity of H. okamotoi. METHODS: T. rubripes, T. niphobles, T. snyderi, and T. pardalis were used for UEA I staining of the gills and an in vivo challenge test against H. okamotoi. To examine the effect of l-fucose, an in vitro detachment test was conducted using the host's gills. Additionally, fucosylated proteins were isolated from the membrane proteins of T. niphobles gills. RESULTS: The location of l-fucoside and the infection dynamics in four species were correlated to some extent; H. okamotoi detached relatively quickly from T. niphobles possessing l-fucoside both on the surface of the gills and in certain types of cells, including mucus cells, but detached slowly from T. snyderi possessing l-fucoside in only certain types of cells, including mucus cells. Under the conditions examined, H. okamotoi exhibited minimal detachment from T. rubripes and T. pardalis, and l-fucoside was not detected. The significantly higher detachment rate of H. okamotoi from the host's gills incubated in l-fucose-containing medium compared with the controls suggests that l-fucose in the non-host gills induced detachment of H. okamotoi. Four fucosylated proteins, including mucin5AC-like, were identified as potential factors for the detachment of H. okamotoi. CONCLUSIONS: Fucosylated proteins covering the surface of non-host gills might contribute to H. okamotoi detachment. GENERAL SIGNIFICANCE: This research shows the possible involvement of oligosaccharides in the host specificity of monogenean parasites.

Myxobolus coriumicus n.sp. (Cnidaria: Myxozoa) Causing Scale Disease Associated with Skin Lesions in Indian Cultured Carp, Cirrhinus mrigala in Punjab.

PURPOSE: The motive of the present study was to investigate incidences of myxozoan parasite infection in commercially important fishes and their characterization using morphological attributes and molecular approach. METHODS: The specimens of cultured Cirrhinus mrigala were sampled and various organs were examined. The plasmodia were detected on the scales. The identification of species was based on the myxospore morphology and 18S rDNA sequence analyses. For phylogenetic analysis, maximum likelihood (ML) and Bayesian inference (BI) methods were employed. The SEM and histological studies were performed to assess the damage to the scales. RESULTS: The infected fishes had white patches on the scales and red haemorrhagic lesions on the skin. The plasmodia of Myxobolus coriumicus n. sp. were located on the dorsal surface of the scale towards its exposed part. SEM study indicated that lepidonts were damaged in the infected scales. The myxospores were spherical in shape, 9.0-10.0 × 8.0-9.0 [Formula: see text]m in size, with two ovoid equal polar capsules 3.13-4.0 × 2.03-2.33 [Formula: see text]m in size, having 4-5 sutural edge markings at the posterior-lateral margins of the shell valves and binucleated sporoplasm. BLAST search based on 18S rDNA revealed 93.87% sequence similarity with M. rewensis, (MZ230381). The prevalence of infection was 6.3% and Scale Plasmodium Index (SPI) was 3 indicating heavy infection. CONCLUSION: Morpho-molecular data generated during this study enables us to conclude that the present species, M. coriumicus n. sp. infecting scales of C. mrigala is new to the science causing significant damage to the scales.

Integrative taxonomy of Urocleidoides spp. (Monogenoidea: Dactylogyridae) parasites of characiform and gymnotiform fishes from the coastal drainages of the Eastern Amazon, Brazil.

Eight species (four new) of Urocleidoides are reported from Characiformes and Gymnotiformes fishes of the coastal drainages of the Eastern Amazon. Urocleidoides vanini n. sp. is characterized by having a male copulatory organ (MCO) with three and a half counterclockwise rings, absence of vaginal sclerite, and a V-shaped ventral bar. Urocleidoides atilaiamarinoi n. sp. has MCO with two and a half counterclockwise rings, dumbbell-shaped accessory piece, similar anchors, open V-shaped ventral bar, and open U-shaped dorsal bar. Urocleidoides macrosoma n. sp. exhibits an elongate and robust body, MCO comprising one counterclockwise ring, similar anchors with wavy point, and dumbbell-shaped ventral and dorsal bars. Urocleidoides nataliapasternakae n. sp. has MCO comprising two and a half counterclockwise rings, vaginal canal convoluted, point of the dorsal anchor with ornamentation as sclerotized shredded filaments, elongate dumbbell-shaped ventral bar, and U-shaped dorsal bar. Urocleidoides naris and Urocleidoides brasiliensis from H. malabaricus (Characiformes) and the incertae sedis species, Urocleidoides gymnotus and Urocleidoides carapus, from Sternopygus macrurus (Gymnotiformes) are reported, and their molecular sequences are presented in this study. Phylogenetic analyses based on molecular data (28S rDNA and COI mtDNA) reveal that species of Urocleidoides lacking vaginal sclerite are closely related to species that possess vaginal sclerite, suggesting that the absence of vaginal sclerite in Urocleidoides may be the result of a secondary loss. The relationships between species of Urocleidoides and other Neotropical dactylogyrids are also addressed.