Ultrastructural characteristics of the sporogenesis of genus Myxobolus infecting some Nile fishes in Egypt

Fins infestation induced by Myxobolus xiantaoensis in yellow catfish Tachysurus fulvidraco Richardson, 1846: Some pathophysiological and molecular insights

The myxozoan parasite Myxobolus xiantaoensis is a fin pathogen of commercially important yellow catfish Tachysurus fulvidraco Richardson, 1846, in the freshwater ponds of China. In the present work, four geographical isolates of M. xiantaoensis were sampled from the fins of yellow catfish. It was found that the spores of four isolates exhibited few markable differences in morphometrics. The small subunit ribosomal DNA (SSU rDNA) sequences of four isolates were conspecific to the SSU rDNA sequence of M. xiantaoensis. No genetic level variation was observed, even in the characteristically more variable internal transcribed spacer (ITS) region. This absence of variability suggests high gene flow as a result of panmixia in the parasitic populations. ITS phylogeny placed four isolates of M. xiantaoensis in a clade together with myxozoans species infecting Siluriformes. The M. xiantaoensis infection inflicted severe hemorrhages on epidermis of ray-fins, which grew into inflammatory epithelial hyperplasia and lytic cartilage signs. The histochemical analysis of infected fins biopsies is characterized by damage of collagen components of cartilage, resulting in weakness, breaks, and missing fin rays. These tissue sections also had a remarkable inflammatory response around the fin cartilage, with the absence of mature spores and chondrocytes. These results indicate that the fin cartilage damage appeared before the development of tissue inflammation and the parasitic infestation of the fins. The present four geographical isolates of M. xiantaoensis were identified by a holistic approach of species characterization based on biological, morphological, and molecular evidence. These four isolates showed some morphological and genetic variations but within the intraspecific range.

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.

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

Forty-three out of 120 (35.8%) Clarias garipenus fish were found to be naturally infected with Henneguya suprabanchiae. The infection appeared as clusters of ovoid to ellipsoidal plasmodia being embedded within the hyaline cartilage of the suprabranchial organ of the fish. Histological studies indicate tissue distortion at the sites of infection. The continuous growth of the plasmodium led to deformation of the filament structure as well as disorganization and displacement of the gill lamellae. Also, a severe atrophy occurred in the hyaline cartilage of the gills and also in the gill lamellae. Based on the structure and measurements of fresh spores by light microscopy, this parasite was identified as H. suprabranchiae. Spores are oval in shape, and they measure 13 (11-14) × 3 (2-5) μm length by width. It has two polar capsules inside, each measures 3 (2.5-5) × 1 (1.5-4) μm length by width. Each polar capsule has a spirally coiled (7-9 turns) polar filament. The ultrastructural analysis showed that the plasmodia were surrounded by single-unit membrane. The generative cells and the early developmental stages were arranged at the periphery of the plasmodia, while immature and mature spores were centrally arranged. The developmental stages characterizing sporogenesis, capsulogenisis, and valvogenesis of the present parasite were ultrastructurally studied. The small subunit 18 S rDNA (SSU rDNA) gene sequences from different isolates was sequenced and compared with the sequence of the same gene from the Henneguya sp. isolated from GenBank. The phylogenetic position of the present Henneguya sp. within the genus was determined using sequence analysis of all related taxa available in GenBank, and the phylogenetic tree derived from this study is elucidated and compared with the current taxonomy of the available myxosporeans. Comparison of the nucleotide sequences and divergence showed that the SSU rDNA gene of this Henneguya species revealed 92.2% sequence identity with Henneguya exilis (acc. no. AF021881) differing in 30 nucleotides with lower divergence value.

Ultrastructure and host parasite relationships of Kudoa pagrusi (Myxozoa) infecting the heart muscles of sea bream Pagrus pagrus (L.) from the Red Sea

The present study is a part of a continuous investigation of myxosporean parasites-infecting fish of the Red Sea using light and electron microscopy. Out of 120, 80 (67%) Pagrus pagrus fish were found to be naturally infected with Kudoa pagrusi. The infection was intensive and appeared as clusters of ovoid to ellipsoidal plasmodia being restricted to the cardiac muscles. Histological studies elaborated tissue distortion at the sites of infection and the adjacent layers. The development of the plasmodia reduced the functional area of the heart muscle. Ultrastructural analysis showed that the plasmodia were surrounded by single-unit membrane with numerous projections and pinocytotic channels extended toward the host cell. The generative cells and the different developmental stages were arranged at the periphery of the plasmodia while immature and mature spores were centrally arranged. The present study showed the main criteria of this genus: the spores possess four polar capsules with four shell valves.

Light and electron microscopic study on Henneguya suprabranchiae Landsberg, 1987 (Myxozoa: Myxosporea) infecting Oreochromis niloticus, a new host record

Out of 58 live tilapia fish, five Oreochromis niloticus were found to be naturally infected with Henneguya suprabranchiae (8.62%). Such infection was recorded only during winter season from Bahr Shebin, a tributary of the River Nile at Menoufia Governorate, Nile Delta, Egypt. Based on the structure and measurements of fresh spores, this parasite was identified as H. suprabranchiae. Spores are oval in shape and they measure 15 (13-16) x 5 (4-6) microm length by width. It has two polar capsules inside and they measure 4 (5-7) x 1 (2-3) microm length by width. Each polar capsule has spirally coiled (7-9 turns) polar filament. The plasmodia as well as all other parasitic stages were described using light and transmission electron microscopy and discussed regarding to those of other fish hosts especially those of Africa.