Morphology and small subunit ribosomal DNA sequence of Henneguya suprabranchiae (Myxozoa), a parasite of the catfish Clarias gariepinus (Clariidae) from the River Nile, Egypt

Novel insights into immune stress markers associated with myxosporeans gill infection in Nile tilapia (molecular and immunohistochemical studies)

Nile tilapia (Oreochromis niloticus) is valued in aquaculture because of its quick development and ability to thrive in various environments. Myxosporeans are among the fish parasites that affect fish productivity, as they impact fish growth and reproduction, resulting in large fish deaths in farms and hatcheries. This study has been focused on morpho-molecular identification for the myxosporean parasites infecting Nile tilapia from three governorates in Egypt and assessment of gene expression of different cytokines (Interleukin-1βeta (IL-1β), major histocompatibility complex class II (MHC-II), and clusters of differentiation 4 (CD-4) and 8 (CD-8)) in tissues. Additionally, this work aimed to correlate the developed histopathological alterations and inflammatory reactions in gills with immunohistochemical expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-α). Finally, the infected fish's cortisol levels and blood glucose were assessed. Results of BLAST sequence analysis of the 18S rRNA for the collected protozoans confirmed Myxobolus agolus, M. brachysporus, M. tilapiae, and Henneguya species. The molecular characterization of the immunological status of gills revealed marked upregulation of different inflammatory cytokines in the gills of infected fish. There was a significantly increased serum cortisol and glucose level in infected fish compared with control, non-infected ones. Severe histopathological alterations were observed in the infected fish gills, associated with increased expression of iNOS and TNF-α and related to myxosporean infection. The present study provides new insights into oxidative stress biomarkers in Nile tilapia infected with Myxosporeans and elucidates the gill's immune status changes as a portal of entry for protozoa that contribute to tissue damage.

Characterizing Two New Henneguya Species in the Respiratory Organs of African Sharptooth Catfish

Henneguya species are myxozoans, a suborder of Cnidaria, which can affect the gills and extrarespiratory organs of the African sharptooth catfish, Clarias gariepinus. This research describes natural infection-induced histological alterations caused by the Henneguya species present. The Henneguya species were also identified molecularly using DNA sequenced from infected tissue cysts, and phylogenetically analyzed. Clinical investigations revealed cyst-like nodules on the fish gill filaments and extrarespiratory organs. Within a milky fluid inside the cysts were several Henneguya-like spores. Henneguya sp. infested 27.5% of the fish, with the highest prevalence in the gills compared to the extrarespiratory organs. The Henneguya species parasitized the gill and the dendritic tissues, resulting in histopathological characteristics. The plasmodia's developmental stages resulted in destructive damage which manifested as marked necrosis, which was replaced by a focal aggregation of inflammatory cells. Amplification of the 18S ribosomal DNA from the fish parasites was followed by sequencing, which confirmed their identities as new species Henneguya qenabranchiae n. sp. and Henneguya qenasuprabranchiae n. sp. with 99.53 and 99.64% identities, respectively, to Henneguya sp. 1 HS-2015. The two C. gariepinus myxozoans shared some characteristics based on morphologic and phylogenetic analysis as previously published, where it was proposed that they were a sister lineage to Henneguya species in Egypt, and it is now proposed that they are new species.

Henneguya species infecting the gastrointestinal tract of Clarias gariepinus from the Nile River

As part of a study on parasitic infection in the African sharptooth catfish Clarias gariepinus, we found cysts of varying sizes in the stomach and intestine that contained myxospores with morphological features resembling those of the genus Henneguya. The present investigation was carried out with data on spore morphology and histopathology. Additionally, the myxozoan was identified using a molecular-based approach with 18S small subunit rDNA sequences. Based on the morphological characterization and tissue specificity of Myxozoa, 2 species of Henneguya were identified in the catfish stomach and intestine. Several histopathological changes were observed in the intestine which may affect fish performance and survival. The phylogenetic position of nucleotide sequences of the Henneguya species identified here were clustered with other fish-infecting Henneguya species. These sequences were deposited in GenBank. It appears that they potentially represent 2 species, denominated Henneguya sp. 1 and Henneguya sp. 2 according to the samples originating from the stomach and intestine, respectively. Although future investigations are needed for detailed morphological and molecular descriptions, this study documents the likely occurrence of infection with Henneguya noted for the first time, to our knowledge, in the digestive system of C. gariepinus in Egypt.

Characterisation of myxozoan fauna of western mosquitofish, Gambusia affinis (Baird and Gerard) (Cyprinodontiformes: Poeciliidae), inhabiting experimental catfish ponds in Mississippi, USA

Characterising myxozoan taxa parasitising fish hosts in catfish aquaculture ponds is crucial to understanding myxozoan community dynamics in these diverse and complex ecological systems. This work investigated the myxozoan fauna of the western mosquitofish, Gambusia affinis, a common, incidental species found in catfish aquaculture ponds in the southeastern United States. 598 fish were sampled in May of 2018 and 2019 from the pond facility of the Thad Cochran National Warmwater Aquaculture Center in Stoneville, Mississippi, USA. Fish were examined microscopically using wet mount preparations of fresh tissue and histology for myxozoans. 18S rRNA gene sequences were amplified from myxospores obtained at necropsy. Updated morphologic, histologic, and 18S rRNA gene sequence features are provided for Henneguya gambusi, Myxobolus pharyngeus, and Myxidium phyllium. Two potentially novel myxozoans were observed during this survey, an undocumented Myxobolus sp. associated with chondrolysis of bones throughout the body and a putative Myxobilatus sp. observed histologically in the renal tubules, ureters, and urinary bladder. However, inadequate samples were obtained for proper species descriptions. Lastly, the life cycle of M. pharyngeus, which is thought to utilize the oligochaete worm Dero digitata as their definitive host, was putatively confirmed by 18S rRNA sequence matching to actinospore stages from oligochaetes in catfish ponds in Mississippi. This work provides novel and expanded morphologic, histologic, molecular and biologic data of five myxozoan parasites of G. affinis, expanding our knowledge of myxozoan diversity in catfish aquaculture ponds.

Henneguya sacacaensis n. sp. (Myxozoa: Myxosporea) parasitizing gills of the acará bicudo Satanoperca jurupari (Osteichthyes: Cichlidae) in eastern Amazon

This study describes Henneguya sacacaensis n. sp. in specimens of the Osteichthyes Satanoperca jurupari (Heckel, 1840), collected in the Rio Curiaú Environmental Protection Area in the city of Macapá, state of Amapá Brazil. Using optical microscopy and molecular analysis, these cyst-shaped parasites were analyzed. The gills of 57.14% of the analyzed S. jurupari contained hundreds of spores. The cysts found on the gill lamellae were oval-shaped and whitish. The Henneguya spores had an average length of 46.5 (41.3-56.92) µm. The fusiform body of the Henneguya measured 16.5 (13.16-20.01) µm long and 5.1 (3.91-6.12) µm in width, the two polar capsules had a taper of 3.83 (3.4-4.32) µm and a width of 1.68 (1.4-1.99) µm, and the tail measured 30 (22.47-41.67) µm in length, containing a polar filament coiled seven to nine times. Morphogical and phylogenetic analysis allowed the preposition of a new species, Henneguya sacacaensis n. sp, that belongs to the family Myxobolidae and the genus Henneguya.

Morphological and Molecular Identification of a Novel Species, Ceratomyxa siganicola n. sp. (Myxozoa: Ceratomyxidae) from Siganus fuscescens, in East China Sea

INTRODUCTION

Ceratomyxa Thélohan, 1892 is one of the largest genera under Myxosporea Butschli, 1881, and has a worldwide distribution, but little attention has been paid to myxosporean parasites from the Chinese seawaters, East China Sea.

METHODS

Morphology and molecular biology methods were combined for species identification and phylogenetic analysis.

RESULTS

A new coelozoic myxosporean species, Ceratomyxa siganicola n. sp., was found to infect the gallbladder of Siganus fuscescens (Houttuyn, 1782) (Perciformes, Siganidae) from coastal waters of Xiamen, East China Sea, China. Mature myxospores of the novel species exhibited the morphologically typical features of the genus Ceratomyxa. They were slightly crescent shaped with rounded ends, measuring 5.6 ± 0.5 (4.8-6.5) μm in length and 19.1 ± 1.8 (16.0-22.1) μm in thickness. The posterior angle was slightly convex to straight and measured 177.1 ± 0.5 (175.2-178.4)°. Spore valves were slightly unequal and smoothly ovoid in the lateral view. Two polar capsules were spherical, equal in size and measured 2.7 ± 0.2 (2.1-3.0) μm in diameter. The 18S rDNA sequence of C. siganicola n. sp. was unique among all myxozoans, and the highest similarity was 97.4% with Ceratomyxa barnesi. Phylogenetic analysis showed that C. siganicola n. sp. was clustered within the clade of siganid ceratomyxids. The present results also indicated that the species radiation of Ceratomyxa occurred not only within host affinity but also within locality.

Morphology and 18S rDNA sequencing of Henneguya peruviensis n. sp. (Cnidaria: Myxosporea), a parasite of the Amazonian ornamental fish Hyphessobrycon loretoensis from Peru: A myxosporean dispersal approach

Myxosporean are endoparasitic cnidarians of wide distribution and responsible for important economic losses in fisheries and aquaculture. A new myxosporean species, Henneguya peruviensis n. sp., is herein described as obtained from the gill filaments of Hyphessobrycon loretoensis caught in the Nanay River, Department of Loreto, Peru. The parasite was found in 37 of 45 (82.2%) examined H. loretoensis. The new species was characterized based on morphological features and 18S rDNA gene sequence data. The sequencing of the 18S rDNA gene from the spores of H. peruviensis n. sp. resulted in 1632 nucleotides and this sequence did not match any of the myxozoan available in the GenBank. Phylogenetic analysis showed that H. peruviensis n. sp. closed together with H. leporinicola. Nonetheless, the 18S rDNA sequences of H. peruviensis n. sp. and H. leporinicola have only 82% similarity. This is the first description and molecular study of a Myxozoa parasitizing fish of the genus Hyphessobrycon in the Amazon basin. Given the importance of the ornamental fish industry in translocation of aquatic organisms worldwide, the international movement of myxosporeans in infected fish is discussed in terms of disease outbreaks and the need for preventative action.

Morphology and small subunit rDNA-based phylogeny of a new Henneguya species, infecting the ornamental fish Corydoras leucomelas from the Peruvian Amazon

A new species of Myxosporea, Henneguya loreotoensis n. sp. is described parasitizing the gill filaments from 17 of 35 specimens (48.5%) of Corydoras leucomelas (Siluriformes: Callichthyidae) caught in the Nanay River, near village Ninarumi, in the Loreto state, Peru. Mature spores were ellipsoidal in shape from the frontal view, measuring 36.2±0.1μm (36.1-36.3) in total length, 14.3±0.1μm (14.2-14.4) in body length, 5.1±0.1μm (4.9-5.3) in width and 21.9±0.1μm (21.8-22.0) in the caudal process. The two polar capsules were symmetrical and elongated, measuring 5.1±0.1μm (4.9-5.3) in length and 2.4±0.2μm (2.1-2.7) in width, containing a polar filament with five coils arranged obliquely to the longitudinal axis. The sporoplasm was binucleate. Partial sequencing of the ssu-rDNA of H. loretoensis n. sp. resulted in a total of 1676 nucleotides, and this sequence did not match any of the myxozoan available in the GenBank. The phylogenetic analysis shows H. loretoensis n. sp. as a sister species of Henneguya paraensis, another amazonian myxozoan parasite of Cichla temensis (Perciformes: Cichlidae).

Myxobolus sp. and Henneguya sp. (Cnidaria: Myxobolidae) natural co-infection in the kidney of Piaractus mesopotamicus (Characiformes: Serrasalmidae)

This study evaluated the myxozoan infection and histopathology of the kidney of freshwater fish Piaractus mesopotamicus from intensive fish farming in Brazil. A total of 55 fish were examined for myxozoan infection. Infected organs were processed by usual histology and stained with hematoxylin-eosin (H&E) and Ziehl-Neelsen (ZN). From the total of 55 fish analyzed, 47 (85.45%) presented myxospores, being 9.09% (5/55) only with Myxobolus sp., 5.45% (3/55) only with Henneguya sp., and 70.91% (39/55) presenting both parasites. The presence of myxospores was associated with histological alterations in both stromal and renal parenchyma. Myxospores were found mostly in the peritubular interstitial tissue and in low intensity in the glomerulus which caused nuclear hypertrophy and loss of Bowman space. An increase in the glomerular tuft and a reduction in the lumen of the collector tubules were also observed, besides the high number of melanomacrophage cells in the glomerulus. This study reports for the first time detection of myxozoan mixed infection in one organ of pacu and discuss the possible transportation of myxospores in the circulating blood.

Morphological and molecular characterization of a new cyprinid gall bladder-infecting Chloromyxum species, Chloromyxum peleci sp. n. (Myxozoa: Chloromyxidae), from Pelecus cultratus (L.) in Russia

Extensive sampling to get rich data is very important to resolve the current taxonomic problem of Chloromyxum genus and elucidate the nature phylogenetic relationships among congeneric species. During the parasitological survey of cyprinid fish in Gulf of Finland off the coast of St. Petersburg, a new Chloromyxum species, named as Chloromyxum peleci sp. n., was found to infect the gall bladder of sichel, Pelecus cultratus (L.). Here, we provided the morphological, ultrastructural, and molecular features to describe it. Infection was represented by mono- or disporic plasmodia and mature free-floating spores in the gall bladder. Mature spores are typical of freshwater Chloromyxum species, spherical or subspherical in lateral view, measuring 8.8 ± 0.5 μm (7.4-9.5) in length, 7.8 ± 0.3 μm (7.0-8.8) in width, and 7.5 ± 0.4 μm (6.8-8.2) in thickness. Spores have a cog-like appearance in apical view for sutural ridge, and eight to ten widely spaced extrasutural ridges per valve protrude from the spore valve margin. The surface ridge patterns of the new species are similar with those of Chloromyxum auratum and Chloromyxum cristatum, with some branching. Four polar capsules of slightly unequal in two pairs were oval in apical view and pyriform in side view, locating at the anterior end of the spores. Polar filaments coil with four to five turns. The obtained almost full length of 18S ribosomal DNA (rDNA) of Ch. peleci sp. n. does not match any sequences available in GenBank but was most closely related to that of Chloromyxum fluviatile (97.9%). Phylogenetic analysis indicated that Ch. peleci sp. n. clustered in a Chloromyxum subclade infecting the gall bladder of freshwater teleost, with robust nodal support. However, Chloromyxum sensu lato infecting gall bladder of freshwater teleost was again proved to be polyphyletic. The possible evolutionary history of Chloromyxum morphotype of Chloromyxum sensu lato was discussed based on the rDNA-referred phylogeny. This is the second Chloromyxum species from sichel.

Morphological and genetic characterization of Kudoa whippsi (Myxosporea: Multivalvulida) from Cheilodactylus zonatus in the western Pacific Ocean off Japan, and two new Kudoa spp. (K. akihitoi n. sp. and K. empressmichikoae n. sp.) from Acanthogobius hasta in the Sea of Ariake, Japan

Molecular genetic characterization using the ribosomal RNA (rDNA) gene accrues a wealth of knowledge regarding the true nature of species diversity of Kudoa Meglitsch, 1947 (Myxozoa: Myxosporea: Multivalvulida) and the biogeographical relationships of isolates from different host fish and sea areas. In the present study, we characterized morphologically and genetically three Kudoa spp. with four shell valves and polar capsules (SV/PC), forming pseudocysts in the myofiber of trunk muscles of Cheilodactylus zonatus or Acanthogobius hasta in the natural seawater around Japan. Myxospores from C. zonatus fished in the western Pacific Ocean off Kochi, Japan, were unequal quadrangular pyramids with one large and three smaller SV/PC, morphologically closest to Kudoa whippsi recorded in various pomacentrid and apogonid fish from the Australian Coral Sea. The 18S and 28S rDNA nucleotide sequences of the Japanese isolate were highly similar to some Australian K. whippsi isolates, but also displayed less similarity to other K. whippsi isolates from the same sea mainly due to instability of nucleotides at certain base positions and/or segments of different isolates. All the K. whippsi isolates including the present Japanese isolate, however, were distinct from Kudoa gunterae, K. whippsi's closest kudoid species in morphology, molecular phylogeny, and biogeography. Our detection of K. whippsi from C. zonatus in the natural seawater around Japan is a new host and geographical record. Kudoid myxospores from A. hasta from the Sea of Ariake, a deep bay of the western part of Japan, exhibited two morphotypes, one resembling K. whippsi and the other Kudoa quadricornis with distinct posteriolateral SV projections. However, rDNA nucleotide sequencing revealed that these two Kudoa spp. were distinct from any known congeners; thus, Kudoa akihitoi n. sp. and Kudoa empressmichikoae n. sp. were erected. The morphological differentiation of K. akihitoi n. sp. from multiple Kudoa spp. with scalene stellate myxospores containing one large and three smaller SV/PC was difficult, whereas K. empressmichikoae n. sp. with spherical spore bodies extending small posteriolateral SV projections was distinct from known congeners with similar but elongated spore bodies and PC, i.e., K. quadricornis and Kudoa paraquadricornis, found in the trunk muscle of carangid fish from the Australian Coral Sea.

Molecular and morphological descriptions of Ceratomyxa collarae n. sp. and Ceratomyxa leucosternoni n. sp. from marine ornamental fishes of Indian waters

Two novel species of Ceratomyxa infecting marine ornamental fishes from Indian waters are described. Marine ornamentals, Chaetodon collare and Chaetodon decussatus, collected from Vizhinjam, along the southwest coast of India and Acanthurus leucosternon collected from Lakshadweep islands of Arabian Sea revealed Ceratomyxa infections in their gall bladders. Mature spores of Ceratomyxa from Chaetodon collare and Chaetodon decussatus were elongate and slightly crescentic, with rounded ends, and measured 5.20 ± 0.32 μm in length and 16.32 ± 1.29 μm in thickness. Polar capsules spherical, equal in size and measured 2.23 ± 0.16 μm long and 2.24 ± 0.20 μm wide. Posterior angle measured 157.75 ± 8.650. Principle Component Analysis and molecular analysis using partial SSUrDNA sequences showed the isolates from these two hosts to be identical. Morphological, morphometric and molecular analysis using partial SSUrDNA sequences revealed the taxonomic novelty of isolates and are hence treated as Ceratomyxa collarae n. sp. Mature spores of Ceratomyxa from Acanthurus leucosternon were elongate, slightly tapering with rounded ends, and measured 7.34 ± 0.92 μm in length and 24.37 ± 2.34 μm in thickness. Shell valves were equal, joined by a narrow suture line. Polar capsules spherical in shape, equal in size, 2.59 ± 0.32 μm long and 2.46 ± 0.32 μm wide, and polar filament measured 18.68 ± 2.54 μm. Based on morphological, morphometric and molecular analyses, the present species of Ceratomyxa is distinct, considered as a new species and named Ceratomyxa leucosternoni n. sp. The paper also discusses the prevalence of the recovered parasites and host specificity of Ceratomyxa collarae n. sp.

Ultrastructural, ssrDNA sequencing of Myxobolus prochilodus and Myxobolus porofilus and details of the interaction with the host Prochilodus lineatus

Myxobolus prochilodus and Myxobolus porofilus are parasites of Prochilodus lineatus, an economically important South American fish found in La Plata and Paraiba do Sul river basins. This study focusing on parasite-host interaction provides an ultrastructural and phylogenetic analysis, the latter based on ssrDNA sequencing of these parasites respectively infecting the gill filaments and fins of P. lineatus taken from the Mogi Guaçu River, São Paulo, Brazil. A total of 13 adult specimens were examined in this study. The prevalence of infection was 7.69 % for M. prochilodus and 15.38 % for M. porofilus. Phylogenetic analysis showed M. prochilodus and M. porofilus clustered in a subclade composed of parasites of the Prochilodontidae family. In M. prochilodus infecting gill filaments, where cellular degeneration in the epithelium was observed, the plasmodia were surrounded by a capsule composed of layers of fibrocyte-like cells, with cellular projections joined to the projections of other fibrocyte-like cells by desmosomes, and more externally typical fibroblast layers. Some granular leukocytes were seen interspersed among these layers. In M. porofilus infecting the fins, the capsule of connective tissue was represented only by loosely arranged collagen fibers, and no granular leucocytes were observed. Finally, several unusual vacuoles with filamentous content and some characteristics usually described as degenerative alterations, as myelin figure, were noted in plasmodia and pansporoblasts of both myxosporean species. The possible influence of inflammatory response and xenobiotics was considered to be the explanation for the alterations observed in Myxobolus species and its host.

Histological location of myxosporean plasmodia in fish tissue with Luna's method

In the present study, a staining technique, Luna's method, has been used for detection and tissue location of myxosporean spores/plasmodia in histological sections of gills and liver. The Luna's staining was performed on the sections of the tissue fixed in Bouin's, embedded in paraffin wax. The mature plasmodia were stained in bright red color and pansporoblasts and gill tissue stained in blue. This staining helped to detect and locate even a single myxospore of less than 15 μm in size located within the tissues of the host.

Prevalence, morphology and scanning electron microscopy study of myxozoan parasites

The present study was conducted from Garia, West Bengal, India to study the Prevalence, Morphology, Severity of infestation and Scanning Electron Microscopy of Myxozoan parasites in Indian Major Carps. A total of 155 fishes were examined, out of which 80 were found infected with myxozoan parasites (51.61 %) and severity of infestation varied from 0.5 to 2. Three known species Myxobolus orissae, M. carnaticus and Thelohanellus caudatus were found infecting various organs such as gills and fins of Indian major carps. Spores of the species, T. caudatus measures 12.84 ± 0.77 (11.4-14.2) μm × 8.5 ± 0.71 (7.6-9.6) μm and was elongated pyriform in shape with rounded posterior and tappering anterior end. Parietal folds were absent. The single polar capsule is rounded to oval shaped with slightly pointed anterior end and broad posterior end with size measuring 6.15 ± 2.09 (4.2-10.4) μm × 3.85 ± 1.18 (2.3-4.9) μm. M. orissae, size of the mature spore measures 15.6-19.7 (17.25) μm × 5.7-9.3 (6.70) μm and was elongated pyriform in shape. Two polar capsules are distinctly unequal. Large one measures 6.8-13.5 (8.75) × 1.4-3.1 (1.90) μm and smaller one 6.9-11.5 (7.44) × 1.7-2.4 (1.57) μm in size. Both are broadly pyriform with pointed pointed anterior end and rounded posterior end. Myxobolus carnaticus mature histozoic spores measures 8.1-12.9 (9.49) × 7.2-10 (8.27) µm are creamy white to yellow in colour tear shaped in valvular view with rounded posterior and bluntly pointed anterior ends.

Morphological and molecular aspects of Ceratomyxa mehlhorni n. sp., a parasite of the golden trevally Gnathanodon speciosus in the Arabian Gulf off the Saudi Arabian coast, with data on its seasonal prevalence

During a survey of the myxosporean fauna of the golden trevally Gnathanodon speciosus from the Arabian Gulf off Saudi Arabia, a species of Ceratomyxa that did not conform to any known species was recorded. The infection was detected as a large number of mature spores free-floating in the bile. Mature spores were hat- or helm-like in the frontal view with two short and unequal valves. The spores measured 8 (7-9) × 12 (10-14). The two polar capsules were spherical, equal in size and measured 3 (2-4) in diameter with three filament turns. Sporoplasm was binucleated and filled the whole extracapsular space. The small subunit ribosomal DNA sequence of this species did not match any available sequences in GenBank. The lowest genetic distance was 0.017, observed with Ceratomyxa moseri infecting Pomacentrus wardi from Australia's Great Barrier Reef. A maximum likelihood phylogenetic tree showed a close association between the new species and a variety of ceratomyxid species, including Ceratomyxa arabica reported from the Arabian Gulf. Given the morphological and molecular differences between this species and other Ceratomyxa spp., we proposed the present form was a new species and the name Ceratomyxa mehlhorni sp. n. for this parasite from the gallbladder of G. speciosus.

Histopathological and ultrastructural studies of a Henneguya species (Myxozoa: Myxosporea) infesting the intestine of Clarias gariepinus from Benin (West Africa)

Fish culture is the best alternative to fill the gap between natural fish catches and estimated needs of populations in animal protein consumption. In West Africa, this goal required to have suitable fishes for aquaculture which are Clariidae and Tilapia. Clarias gariepinus (Clariidae) fetches a higher price than tilapias as it can be sold alive at the market but a high infestation by Henneguya leads to decrease this commercial value. Those reasons lead us to perform studies on seasonal variations, histopathological aspects and life cycle of Henneguya sp. infecting the intestine of C. gariepinus using light and electron microscope. From November 2011 to December 2012, 339 specimens were collected from Ouémé River (Benin) and examined. An overall prevalence of 7.37 % was recorded for plasmodia of Henneguya sp. Parasite occurrence did not vary significantly between seasons (χ(2) = 12.235; df = 3; p > 0.05), nor sexes (χ(2) = 2.992; df = 7; p > 0.05) while differences were significant between classes of weight (χ(2) = 39.929; df = 5; p < 0.05). The highest prevalence was recorded in host ranging from 300 to 374 g. Histopathological analysis showed that the mass continuous development of the plasmodium produced thickening of the intestine wall and compressed neighboring tissues and destroyed villi and smooth muscle layers. The stages of the parasite development including sporogenesis, capsulogenesis, and valvogenesis were asynchronous. Investigations are still running by molecular approaches in order to identify accurately this species.

18S rRNA gene sequencing identifies a novel species of Henneguya parasitizing the gills of the channel catfish (Ictaluridae)

In the southeastern USA, the channel catfish Ictalurus punctatus is a host to at least eight different species of myxozoan parasites belonging to the genus Henneguya, four of which have been characterized molecularly using sequencing of the small subunit ribosomal RNA (SSU rRNA) gene. However, only two of these have confirmed life cycles that involve the oligochaete Dero digitata as the definitive host. During a health screening of farm-raised channel catfish, several fish presented with deformed primary lamellae. Lamellae harbored large, nodular, white pseudocysts 1.25 mm in diameter, and upon rupturing, these pseudocysts released Henneguya myxospores, with a typical lanceolate-shaped spore body, measuring 17.1 ± 1.0 μm (mean ± SD; range = 15.0-19.3 μm) in length and 4.8 ± 0.4 μm (3.7-5.6 μm) in width. Pyriform-shaped polar capsules were 5.8 ± 0.3 μm in length (5.1-6.4 μm) and 1.7 ± 0.1 μm (1.4-1.9 μm) in width. The two caudal processes were 40.0 ± 5.1 μm in length (29.5-50.0 μm) with a spore length of 57.2 ± 4.7 (46.8-66.8 μm). The contiguous SSU rRNA gene sequence obtained from myxospores of five excised cysts did not match any Henneguya sp. in GenBank. The greatest sequence homology (91% over 1,900 bp) was with Henneguya pellis, associated with blister-like lesions on the skin of blue catfish Ictalurus furcatus. Based on the unique combination of pseudocyst and myxospore morphology, tissue location, host, and SSU rRNA gene sequence data, we report this isolate to be a previously unreported species, Henneguya bulbosus sp. nov.

Remarks on the validity of Myxobolus ampullicapsulatus and Myxobolus honghuensis (Myxozoa: Myxosporea) based on SSU rDNA sequences

In the present study, we isolated three populations of Myxobolus ampullicapsulatus from the gills of crucian carp, Carassius auratus auratus, two from Yongchuan, Chongqing area and one from Poyang Lake, Jiangxi area, China, sequenced their complete small subunit ribosome RNA gene, analyzed their genetic distance and gene similarity, and explored their relationship based on Bayesian inference and maximum likelihood analyses of their small subunit ribosomal DNA. The results combined with their morphological characteristics suggest that M. ampullicapsulatus infecting the gills and pharynx of allogynogenetic gibel carp, Carassius auratus gibelio, should be Myxobolus honghuensis. This study highlights the importance of DNA sequence comparisons for distinguishing Myxobolus species and indicates that the intra-species identification for the two Myxobolus species mentioned in the present research should be less than ten variation sites. In morphology, M. honghuensis Liu et al. (2012) parasitic on the gills of C. auratus auratus (goldfish) was collected from Chongqing area, and its mature spore was 16.5–19.5 × 8.5–10.0 μm in size, polar capsule was 7.0–10.0 × 2.5–4.0 μm in size, and polar filament had 9–10 coils. M. honghuensis Liu et al. (2012) isolated from the pharynx of C. auratus gibelio was sampled in Hubei area, and its mature spore was 15.1–19.5 × 9.0–11.3 μm in size, polar capsule was 7.9–8.1 × 3.0–4.5 μm in size, and polar filament had 7–8 coils.

Characterization of active ribosomal RNA harboring MITEs insertion in microsporidian Nosema bombycis genome

Microsporidia are a group of obligate intracellular parasites of medical and agricultural importance, which can infect almost all animals, including human beings. Using the genome data of Nosema bombycis, four families of miniature inverted-repeat transposable elements (MITEs) in ribosomal DNA (rDNA) were characterized in the microsporidian N. bombycis and were named LSUME1, ITSME1, SSUME1, and SSUME2, respectively. The genome-wide investigation of these MITEs shows that these MITEs families distribute randomly in N. bombycis genome. All insertion sequences have conserved characteristics of MITEs, the direct repeat sequence and terminal inverted-repeat sequence at both ends of each MITEs sequence. Additionally, using the CLC RNA Workbench Software, secondary structures of rRNA containing MITEs sequence have been predicted and were located in variable region or expansion segment. Furthermore, using two different probes, one is prepared by MITE sequence only (short probe) and the other is prepared by MITE sequence flanking partial rDNA sequence (long probe); northern blotting and dot blotting have been performed to detect the transcriptional and functional activity of the rDNA containing MITEs insertion. Fortunately, we found that the rDNA, which harbors the MITE, not only can be transcripted but also can form a complete ribosome. This is an interesting thing that one gene can keep active even when it has been inserted with another sequence. But the biological and structural significance of this observation is not readily apparent.

Thelohanellus niloticus sp. nov. (Myxozoa: Myxosporea), a parasite of the Nile carp Labeo niloticus from the River Nile, Egypt

In the present study, the morphology and morphometric characterization of Thelohanellus niloticus sp. nov., a new myxozoan belonging to genus Thelohanellus Kudo, 1933 (Myxosporea, Bivalvulida) infecting the gills of Labeo niloticus (Osteichthyes, Cyprinidae), were described for the first time from the River Nile at El-Minia Governorate, Egypt. Forty-one out of 78 (52.6 %) of the examined fish were infected. The infection was observed as irregular, milky whitish, cyst-like plasmodia (up to 0.8 mm in diameter) attached to the gill filaments of the host fish. These plasmodia contained tear-shaped myxospores with slightly tapering anterior and rounded posterior ends. Each spore has a single pyriform polar capsule. Spores measured about 23.3 ± 0.3 (20.4-27.1) μm long and 13.4 ± 0.4 (11.5-14.2) μm wide. The polar capsule was 11.7 ± 0.3 (9.2-12.5) μm long and 4.7 ± 0.3 (3.5-6.2) μm wide, containing a polar filament coiled perpendicular to the longitudinal axis of the spore body making eight turns. Occasionally, an oblong, irregular-shaped mass of protoplasm with a slightly oval nucleus (1.4 μm in diameter) and a small iodinophilous vacuole measured 0.85 ± 0.2 μm (0.73-1.2 μm) were observed in the spore. Due to the lack of the second polar capsule characterizing Myxobolus sp., the present parasite is placed within the genus Thelohanellus. Based on morphological differences (compared with other members of Thelohanellus Kudo, 1933) and the host specificity, this species is described as a new one of the genus Thelohanellus recorded for the first time in Egypt.