Myxobolus spp. (Cnidaria: Myxozoa) in introduced yellow perch Perca flavescens (Mitchill, 1814)

Morphological and molecular characterisation of two closely related species: Myxobolus tihanyensis n. sp. and Myxobolus sandrae Reuss, 1906

Based on spore morphology and small subunit ribosomal DNA sequences, we describe a new Myxobolus species, Myxobolus tihanyensis n. sp., parasitizing the European perch (Perca fluviatilis) from Lake Balaton in Hungary. The brownish plasmodia were found in various locations of the body, mainly in the muscle adjacent with fins and vertebrae. The spores were ovoid, and measured 9.84 ± 0.38 μm in length, 7.69 ± 0.23 μm in width, and 5.35 ± 0.21 μm in thickness, with 8-10 sutural (edge) markings. The polar capsules were mostly equal in size, with 4.91 ± 0.39 μm in length and 2.27 ± 0.24 μm in width. The polar tubule length is 38.15 μm ± 2.70, and coiled 6-7 times. In particular, these morphological data overlap with those of Myxobolus sandrae Reuss1906 infecting the European perch (Perca fluviatilis), the pikeperch (Sander lucioperca), and the Volga pikeperch (Sander volgensis) according to previous descriptions and the taxonomic data here described. However, the phylogenetic analyses separate the two species as sister clades with 16.8% genetic distance. This study has demonstrated that the two species of Myxobolus exhibit phenotypic similarity while displaying significant genetic divergence. Therefore, the importance of including molecular data in the taxonomic description of myxozoans is emphasized.

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.

Synopsis of the species of Myxobolus (Cnidaria, Myxozoa, Myxosporea) described between 2014 and 2020

A synopsis of the species of Myxobolus Bütschli, 1882 (Cnidaria, Myxosporea, Myxobolidae) described from 2014 up till now is presented. It includes 122 nominal species described all over the world. For each of the species, the most relevant morphological and morphometric data, as well as data are provided related to the location in the host, type host and type locality. The GenBank accession numbers are provided whenever possible, and the spores were redrawn based on the original descriptions. The bibliography includes all the papers containing the species descriptions.

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.

Four novel Myxobolus species (Cnidaria: Myxozoa) infecting Anatolian khramulya Capoeta tinca (Cyprinidae) in northern Turkey

We identified Myxobolus anatolicus Pekmezci, Yardimci, Yilmaz & Polat, 2014 and 4 novel Myxobolus species from the Anatolian khramulya Capoeta tinca (Cyprinidae) in northern Turkey based on morphology, histology, and phylogenetic analysis. M. karaeri sp. nov. plasmodia were observed in the skin doublets between fin rays, the surfaces of the operculum, the gill arch membrane, and in the skin of the fin base. M. samsunensis sp. nov. plasmodia were observed in epithelial tissue inside and on the surface and midline of the gill filaments. M. cakmaki sp. nov. presented as a typical vascular species, which develops in large plasmodia at the end of the gill filaments. The chondrophilic M. ekingeni sp. nov. was detected by histology inside the cartilaginous gill arch and the cartilaginous gill rays of the filaments. Phylogenetic analysis of small subunit ribosomal DNA sequences revealed that M. karaeri sp. nov. and M. samsunensis sp. nov. were clustered with Myxobolus species that infect gills, scales, and fins of cyprinids. M. cakmaki sp. nov. grouped with Myxobolus species that exclusively infect the gills of cyprinids. No molecular data were available for M. ekingeni sp. nov.

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

A new myxobolid species, Myxobolus zaikae n. sp., was found in the connective tissue near the kidney and liver blood vessels of the common roach Rutilus rutilus, while fish myxosporean fauna were being investigated in Lake Baikal, Russia. The parasites were studied on the basis of spore morphology as well as with histological and molecular methods. Mature spores of M. zaikae n. sp. are round or ellipsoidal in the frontal view and lemon-shaped in the lateral view, measuring 11.37 ± 0.11 µm (10.2-14.0 µm) in length, 10.29 ± 0.10 µm (9.6-11.0 µm) in width, and 6.3 ± 0.08 µm (5.8-7.1 µm) in thickness (mean ± SD; n = 50). Polar capsules are equal and pyriform, measuring 4.5 ± 0.07 µm (3.4-5.2 µm) in length and 2.9 ± 0.03 µm (2.6-3.3 µm) in width. Polar capsules contained polar filaments coiled with 5 to 6 turns. Phylogenetic analysis showed that this newly described species clusters with other myxobolid species infecting the connective tissue of different organs from Palearctic cyprinid fish.