Light and electron microscopic studies of Myxobolus stomum n. sp. (Myxosporea: Myxobolidae) infecting the blackspotted grunt Plectorhynicus gaterinus (Forsskal, 1775) in the Red Sea, Egypt

Morphological and molecular description of a new species of Myxobolus (Myxosporea: Myxobolidae) infecting Planiliza macrolepis (Smith, 1846) from India

The present paper describes a novel species of Myxobolus parasitizing the gill filaments of the largescale mullet, Planiliza macrolepis from Cochin backwaters, Kerala, India. The parasite develops in the gill filaments; plasmodia elongated, milky white, measured 1.37-2.18 (1.78 ± 0.35) mm × 0.07-0.12 (0.10 ± 0.02) mm in size. Mature myxospores ovoid in valvular view, biconvex in sutural view with smooth shell valves and measured 6.24-7.02 (6.63 ± 0.23) × 5.01-6.18 (5.68 ± 0.25) μm in size. Polar capsules equal, oval with pointed anterior ends, 3.07-3.58 (3.33 ± 0.12) × 1.68-2.42 (2.09 ± 0.18) μm in size. Polar filaments with 4 coils, measured 29.61 ± 4.75 μm in length when extruded. Sporoplasm binucleate with a rudimentary nucleus and a vacuole. A comparison with related Myxobolus species revealed significant morphological and morphometric differences. In BLASTN and genetic distance analysis, the present parasite showed high divergence with other myxosporean sequences, indicating its molecular uniqueness. In Maximum Likelihood and Bayesian Inference analysis, the present species stands out with M. ramadus as sister branch within the Myxobolus clade. In infected gill filaments, the plasmodia caused swelling/deformation, compression of lamellae and reduction in respiratory surface area. Three of 222 P. macrolepis screened were infected, indicating a prevalence of 1.3%. Considering the morphological, morphometric, molecular and phylogenetic differences with the previously described species of myxosporeans, along with the dissimilarities in host and geographical locations, the present parasite is treated as a new species and the name Myxobolus cochinensis n. sp. is proposed.

Morphological re-description and phylogenetic relationship of five myxosporean species of the family Myxobolidae infecting Nile tilapia

Freshwater fish have a major economic and nutritional importance worldwide. Myxosporeans are highly dangerous parasites that infect different fish species, causing severe damage to a large number of economically important species, especially in aquaculture. We conducted a survey of myxosporean parasites infecting Nile tilapia Oreochromis niloticus (Perciformes: Cichlidae) collected from different localities along the River Nile passing through Giza province, Egypt. Out of 100 fish specimens collected, 45 were found to be naturally infected with these parasites in the region of the trunk kidney. Light microscopic examination revealed the presence of 5 distinct myxosporean species belonging to 2 different genera, viz. Myxobolus and Triangula, belonging to the family Myxobolidae; all 5 species have been previously described. Morphological characteristics, host specificity and geographical distribution, tissue tropism, and molecular analysis of the partial sequence of small subunit ribosomal DNA gene revealed that the recovered myxosporean species described herein were genetically distinct from other myxozoan species but had 95% sequence similarity to M. cerebralis. Also, phylogenetic analysis placed the present myxosporean species in the freshwater Myxobolus clade, which is a sister group of freshwater Myxobolus/Henneguya species.

Histopathological and ultrastructural studies of Myxobolus turpisrotundus from allogynogenetic gibel carp Carassius auratus gibelio in China

During an ongoing systematic survey on species diversity of myxozoans parasitising allogynogenetic gibel carp Carassius auratus gibelio (Bloch) in China, plasmodia were detected in the fins, lip, jaw, gill chamber, gill arches, operculum and oral cavity of infected fish. Combining the morphological and molecular data, the present species was identified as Myxobolus turpisrotundus Zhang, Wang, Li et Gong, 2010. Histopathological examination revealed that despite infecting different organs, M. turpisrotundus always occurred in dermis, demonstrating its affinity to this tissue. Histopathological effect of M. turpisrotundus on the host is relatively mild except parasites in the gill arches producing compression of the adipose tissue and heavy adductor muscles deformation with lymphohistiocytic infiltrates. In addition, the plasmodia in different sites were with the same complex structure arrangement: cup-like cells with unknown derivation, a thin collagenous fibril layer, areolar connective tissue, basement membrane and host epithelial cell. Ultrastructural analysis showed that the parasite has monosporic pansporoblast and sporogenesis followed the usual pattern of most of the myxosporeans.

Ultrastructural description of Myxobolus cuneus (Myxosporea) in the skeletal muscle and kidney of tropical farmed fish Piaractus mesopotamicus (Characiformes: Characidae)

This study characterizes by transmission electron microscopy (TEM) and morphometric features the myxozoan Myxobolus cuneus (Myxosporea) in Piaractus mesopotamicus and reports the skeletal muscle and kidney as site of infection. The register was based in 21 young fish from intensive fish farming in Southeast Brazil and the spores were analyzed in fresh-mounted slides of the infected organs stained with Toluidine blue and processed as usual for TEM. It differs from Myxobolus cunhai from the fish host and different polar capsule size, and from Myxobolus serrasalmi on the pyriform spore shape and an oval macrospore, differently to that reported in this study. Morphometric characteristics and TEM study confirmed the present material as M. cuneus.

Morphological, ultrastructural, and molecular description of Unicapsula fatimae n. sp. (Myxosporea: Trilosporidae) of whitespotted rabbitfish (Siganus canaliculatus) in Omani waters

Investigations regarding the parasite fauna of wild whitespotted rabbitfish (Siganus canaliculatus) Park, 1797 revealed white, spherical, loosely attached cysts measuring 896 (375-1406) μm in diameter in the inner endothelial wall of the esophagus and stomach. Mature spores inside these cysts corresponded to the original description of spores belonging to the genus Unicapsula Davis, 1924. Unicapsula fatimae n. sp. spores were 6.23 (5.60-6.60) μm in length and 6.80 (6.12-7.39) μm in width. The length of large polar capsule was 2.62 (2.18-2.97) μm and width was 2.65 (2.32-2.90) μm, and the extended large polar capsule filament length was 15.50 (11.71-19.99) μm. Transmission electron microscope images of the plasmodia revealed a complex cyst structure that was unique among other Unicapsula spp. Ultrastructural details of the host-parasite interface and developmental stages of a species from the Unicapsula genus are described for the first time. Histology of an infected esophagus revealed some abnormalities and changes in the host tissue around the infection site, including hypertrophy of host esophagus epithelial cells and hyperplasia of host glandular tubules. The parasite presented here has been added to the genus Unicapsula using comparative morphological analysis and ultrastructural investigations supported by 18S small subunit ribosomal DNA molecular analysis.

Prevalence, site and tissue preference of myxozoan parasites infecting gills of cultured fish in Punjab (India)

Native carp species cultured in Indian farms in Punjab (catla Catla catla, rohu Labeo rohita, mrigal Cirrhinus mrigala, exotic carps such as silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella, common carp Cyprinus carpio and a catfish Sperata seenghala) were examined for the presence of myxozoan parasites infecting gills. Firstly, the gills were examined under a zoom-stereomicroscope for the presence of plasmodia. The number of plasmodia per gill was counted to determine the index for the intensity of infection. Infected tissues were processed for histology, and 3-4 µm sections of infected gills were stained with haematoxylin & eosin and Luna's method. A total of 19 species of myxosporean were found infecting various cell types in the gills. Of these, 14 species belonged to the genus Myxobolus, 3 species to the genus Thelohanellus and 2 species to the genus Henneguya. Species belonging to the genus Myxobolus formed the interlamellar and intralamellar vascular (LV) type plasmodia, and species belonging to the genus Thelohanellus and Henneguya formed intrafilamental vascular (FV) type plasmodia. Mixed infections comprising 2, 3 or 4 different myxozoan species were noted in individual fish. The most common type of parasitism was polyparasitism due to 4 myxobolids co-occuring in fish with an infection rate of 23.16%. All species caused mild to severe haemorrhagic gill disease with little clinical symptomatology.

A new myxosporean species Myxobolus sclerii sp. nov. and one known species M. stomum Ali et al. 2003 from two Indian major carp fishes

The present communication deals with description of one new species of Myxobolus (Myxozoa: Myxosporea: Bivalvulida), M. sclerii sp. nov. infecting eye ball of Catla catla (Hamilton) and redescription of M. stomum infecting scales of Labeo rohita (Hamilton), two major carps of Kanjali and Ropar Wetlands respectively. Spores of M. sclerii sp. nov. measure 7.9-9.5(8.7 ± 1.13) × 4.3-5.7(5 ± 0.98) μm in size. Parietal folds absent. Polar capsules two, equal and measuring 4-5.4(4.7 ± 0.98) × 1-2.6(1.8 ± 1.31) μm in size. A rod-shaped medium-sized intercapsular process is present. Iodinophilous vacuole present measuring 2.19-4.13(3.16 ± 1.37) μm in diameter. Spores of M. stomum Ali et al.2003 measure 9.8-10.3(10.0 ± 0.35) × 7.9-8.7(8.3 ± 0.56) μm in size, with rounded anterior and posterior end. Spore valves smooth, symmetrical, thick measuring 0.88 μm in thickness. Parietal folds absent. Two anteriorly situated polar capsules are equal, pear-shaped measuring 4.8-5.2(5.0 ± 0.28) × 1.5-2.3(1.9 ± 0.56) μm in size, each with a neck leading to a fine duct opening independently. Both polar capsules converge slightly anteriorly but diverge apart posteriorly occupying more than half of spore body. Intercapsular appendix is absent. Earlier, the parasite was recorded in the buccal cavity, muscles and lips of Plectorhynchus gaterinus (Forsskal), Egypt. A new locality-Ropar Wetland, a new location-scales and a new host- Labeo rohita (Hamilton) are recorded for this parasite.

Site adaptations of Acanthogyrus (Acanthosentis) tilapiae: observations through light and scanning electron microscopy

Acanthogyrus (Acanthosentis) tilapiae parasites were collected from the intestines of 300 fish belonging to three tilapia species sourced at the River Nile, Giza, Egypt. The proboscis of the parasite was characterized by three rows of hooks that curved towards the posterior of the body. The first row is supported by unmodified hooks. The parasite tegument has a series of alternative folds and a large number of pores. Sensory ganglia are located on the surface of the proboscis and body. Acanthogyrus (Acanthosentis) tilapiae provokes an aggressive host response indicated by hyperplasia of the intestinal goblet cells and focal eosinophil infiltrations. This acanthocephalan parasite shows a highly modified adaptation to its site of host infection.

Zschokkella egyptica n. sp. (Myxosporea: Bivalvulaida) infecting the gallbladder of the eel catfish Plotosus lineatus Thunberg, 1787 and the freckled goatfish Upeneus tragula Richardson, 1846 in the Red Sea, Egypt

A new myxosporean, Zschokkella egyptica n. sp. was found in the gallbladder of two hosts: the eel catfish Plotosus lineatus and the freckled goat fish Upeneus tragula from the Red Sea at Suez City, Egypt. The plasmodia were polysporic, kidney to elliptical shaped with hairy holdfast projection and measured 109 x 70 microm. Mature spores were fusiform with 9 to 11 longitudinal striations. The mean spore dimensions were 13.0 x 10.5 microm. Spherical polar capsules are 4.8 microm in diameter; the polar filament showed four turns and were arranged perpendicular to the longitudinal axis of the capsule.

Myxobolus lubati n. sp. (Myxosporea: Myxobolidae), a new parasite of haffara seabream Rhabdosargus haffara (Forsskal, 1775), Red Sea, Egypt: a light and transmission electron microscopy

A new myxosporean parasite, Myxobolus lubati n. sp., was described from the wall of the intestine of haffara seabream Rhabdosargus haffara (Forsskal 1775), Red Sea, Egypt. Macroscopic plasmodia of about 300 mum diameter were located in the circular muscle layer of the intestine. The spores were ovoid and sometimes ellipsoid and measured 9.8 x 7.2 mum. The shell wall of the spore was thickened at the posterior end and marked with 5-7 sutural markings. Polar capsules were equal and pyriform with three polar filament turns situated in the posterior half of the polar capsule. Polar capsules measured 4.2 x 1.6 mum. Histological evaluation of the infection revealed a slight distention of the intestinal layer of muscularis. Ultrastructure of the plasmodial wall and sporogenesis of the present species followed the usual pattern valid for most studied myxosporean species.

Synopsis of the species of Myxobolus Butschli, 1882 (Myxozoa: Myxosporea: Myxobolidae)

A synopsis of 744 nominal species of Myxobolus Butschli, 1882 (Myxozoa, Myxosporea, Myxobolidae) is presented. For each species, the relevant morphometric and morphological data are indicated, as well as the host(s), site(s) of infection within the host and type-locality.