Morphological, histological, and molecular aspects of Myxobolus zaikae n. sp., a parasite of the roach Rutilus rutilus, in Lake Baikal

Occurrence of Myxobolus spp. (Myxozoa) in the blood of Metynnis lippincottianus (Osteichthyes: Serrasalmidae) from eastern Amazon, Brazil

Myxozoans are obligatory parasites and can be found in various organs and bloodstreams of fish, thus, the objective of this work was to describe the occurrence of Myxobolus spp. in the circulating blood of Metynnis lippincottianus from River Curiaú, Macapá City, eastern Amazon, Brazil. The samples of M. lippincottianus (11) were caught using cast net and gillnets. The fish blood was collected by puncturing the caudal vessel, using needles and syringes containing 10% of EDTA solution. Blood smear were prepared and panchromatic stained with a combination of May Grunwald-Giemsa-Wright, for observation and examination of the parasitic structures in optical microscope. Tissues from the kidney was examined using specific stereoscopic binoculars to check for the presence of cysts, lesions and parasites. The prevalence of Myxobolus spp. infecting the circulating blood of the fish was 36.36% (4/11) and 15 spores of mixosporyds were visualized. Myxobolus spp. had a prevalence of 54.55% (6/11) in host's kidney tissue and the morphometric spores data converge with observed in the blood. The morphological characteristics of the spores in the blood samples revealed two morphotypes of Myxobolus spp. This is the sixth occurrence recorded of Myxobolus spp. infecting fish blood in Brazil.

Effect of 80% ethanol or 10% formalin fixation, freezing at −20 °C and staining on Myxobolus (Myxosporea) spores to be deposited in parasitological collections

The preparation of myxosporeans for the description of myxospores and their preservation as type material in parasitological collections show great variations. Most frequently, formalin and ethanol are used for fixation and Giemsa solution for staining spores. In this work, authors studied the effect of 80% ethanol and 10% formalin fixation, freezing at −20 °C and staining on the size and transparency of two Myxobolus species of cyprinid fishes, M. bramae and M. bliccae spore, and recommended a new method for the deposition of type material to parasitological collections in museums. The studies have commended that fresh spores from mature plasmodia are the best material for measuring the size and studying the inner structures, the number of polar tubules in polar capsules and the morphological characters of the intercapsular appendix. The obtained quantitative data suggest that cryo- and chemical preservation do not have a notable negative effect on spores compared to fresh samples but they decrease the transparency of spores. Staining the spores with Ziehl–Neelsen has proved to be a useful method for studying the fine structure without size reduction, while Giemsa staining induced a shrinkage of spores so it seems to be not ideal for description of a new species. When treating spores of Myxobolus spp. with Lugol's solution, iodinophilous vacuoles in the sporoplasm were not recognised but visualisation of the coils of polar tubules was enhanced. As a type material for newly described species, authors suggest phototypes and spores fixed in 80% ethanol to be deposited into collections, as this preservation method is suitable for subsequent research, such as re-measurements and molecular analysis.

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The effect of fixation, freezing at −20 C and staining on myxospores was studied.

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Model materials were myxospores of Myxobolus bramae and M. bliccae.

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No changes in size were observed on frozen at −20 C and 80% ethanol- or 10% formalin-fixed spores.

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A shrinkage of spores was noticed when staining spores with Giemsa solution.

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Phototypes and 80% ethanol-fixed spores are recommended for collections as type material.

Phylogenetic analysis and characterization of a new parasitic cnidarian (Myxosporea: Myxobolidae) parasitizing skin of the giant mottled eel from the Solomon Islands

Myxosporeans are microscopic cnidarians associated with severe diseases in aquaculture and wild fish populations. This group of parasitic cnidarians thus warrants close attention concerning its potential impact on susceptible fish stocks. At present, little is known about this group of parasites infecting anguillid eels. From myxospore specimens collected from a freshwater eel (Anguilla marmorata) in the Solomon Islands, we describe a new species belonging to the genus Myxobolus based on an integrative taxonomic analysis of morphological, biological traits and molecular data. Furthermore, we determined the phylogenetic position and relationships of this species among other platysporine myxosporeans. Molecular phylogenetic assessment of small subunit ribosomal DNA showed that the species clusters together with Myxobolus portucalensis and Echinactinomyxon type 5 Özer, Wootten and Shinn, 2002, in a well-supported subclade. This is the first report of a myxosporean parasite infecting fish from the Solomon Islands.

Novel and known myxobolids (Cnidaria, Myxozoa) infecting Chondrostoma angorense (Cypriniformes: Leuciscidae) in Turkey

Turkey has more than 200 endemic freshwater fish species, one of which is the Ankara nase, Chondrostoma angorense Elvira, 1987 (Cypriniformes: Leuciscidae), a food fish in northern Turkey. Like most endemic fish species in Turkey, its myxosporean parasite fauna (Cnidaria: Myxosporea) are not yet described. We surveyed twenty C. angorense from Lâdik Lake in northern Turkey, and identified two myxosporean parasites from gills of these fish: Myxobolus arrabonensis Cech, Borzák, Molnár, Székely, 2015, and a co-infection of a novel species, Myxobolus polati sp. nov. We characterized both infections based on myxospore morphology, morphometry, tissue tropism, small subunit ribosomal DNA sequence and phylogenetic analysis. Plasmodia of both species were observed in gills, but had distinct tropism: M. arrabonensis is an intrafilamental vascular type, and M. polati sp. nov. is an intralamellar vascular type. We identified M. arrabonensis on the basis of myxospore characters and 100% similarity to the type DNA sequence from the closely-related host C. nasus. The small subunit ribosomal DNA sequence of M. polati sp. nov. (1946 base pairs; GenBank Accession number MH392318) had a maximum similarity of 98% with any Myxobolus sp. from other Eurasian cypriniforms. Phylogenetic analysis revealed that M. polati sp. nov. is most closely related to gill-infecting Myxobolus diversicapsularis from Rutilus rutilus (L.). The present study is the first record of myxosporean species infecting C. angorense comprising a novel species, M. polati sp. nov. and a known species M. arrabonensis.