Comparative morphological and molecular studies on Myxobolus spp. infecting chub from the River Danube, Hungary, and description of M. muellericus sp. n.

Abstract

During a survey on fishes from the River Danube, the occurrence of 8 Myxobolus species (Myxozoa: Myxobolidae) was registered in chub Leuciscus cephalus L. Most species had a specific location within the fish host. M. cycloides was found in the wall of the swimbladder; the branched plasmodia of M. dujardini were located typically in the epithelium of the non-lamellar part of gill filaments; the plasmodia of M. ellipsoides infected fins between 2 fin rays; M. muelleri and Myxobolus sp. 2 formed large elongated plasmodia in the afferent gill artery of filaments, while the round cysts of M. muellericus sp. n. filled the capillary network of the gill lamellae. Intramuscular plasmodia of M. pseudodispar proved to be the most common, although large cysts of Myxobolus sp. 1 were also frequently found in the intestinal wall. Despite similarities of some species in spore morphology, 18S rDNA sequences showed clear differences between the species examined.KEY WORDS: Myxozoa · Occurrence · Histology · Site selection · Molecular phylogeny Resale or republication not permitted without written consent of the publisherDis Aquat Org 73: [49][50][51][52][53][54][55][56][57][58][59][60][61] 2006 relatively strict host specificity, such as M. drjagini Achmerov, 1954, which forms plasmodia only in Hypophthalmichthys molitrix and does not develop in its closely related cyprinid species, H. nobilis. On the other hand, M. cerebralis Hofer, 1903 has a wide host range and infects several salmonid fishes (Hoffman 1999), although experiments performed by El-Matbouli et al. (1999) proved that there were important differences in the susceptibility of different salmonids to M. cerebralis. Moreover, the lake trout Salvelinus namaycush seems to be resistant to M. cerebralis, as has been reported by Blazer et al. (2004) on the basis of in vivo experiments.Similarly, little is known about the affinity to different fish tissues of Myxobolus spp. infecting chub. For M. cycloides infection, Holzer & Schachner (2002) reported a special swimbladder location. Molnár (1994) suggested that most myxozoans had a well-defined tissue and organ specificity. The variations of locations in gills and fins, and the tissue preferences of different Myxobolus species were summarised by Molnár (2002a,b). This author differentiated developments in the gill arch, gill filaments and gill lamellae as locations typical of different species. Gill-infecting Myxobolus spp. from cyprinids in Hungary were also studied by molecular biological methods. The phylogenetic positions of Myxobolus species examined showed that there was a correlation between site preference and the genetic relationships among Myxobolus species (Eszterbauer 2004).Our paper presents data on the spore morphology and molecular biology of 8 Myxobolus species found in chub, on the typical locations of infection and the histological changes caused by it. In addition, the authors describe M. muellericus sp. n. on the basis of molecular biological findings and the location of plasmodia within fish ...

Myxobolus taibaiensis sp. n. (Myxozoa: Myxosporea) infecting the intestinal wall of common carp Cyprinus carpio Linnaeus in China

“…Our result also support the previous conclusion that tissue specificity of sporulation can truly indicate evolutionary relationship (Molnár et al 2006(Molnár et al , 2009, because M. taibaiensis and M. cyprinicola, with different tissue tropism, appear in two different clades. Interestingly, M. shantungensis showed close genetic affinity with M. taibaiensis, although M. shantungensis was reported from gill arches of common carp and is morphological different from the new species.…”

“…(Molnár 2002, Fiala 2006. About 60 among more than 800 species of Myxobolus were found to infect fish intestine (Eiras et al 2005(Eiras et al , 2014, but only five species were described by the current approach (Molnár et al 2006, 2009, Liu 2014, Liu et al 2016a. These are M. shaharomae Molnár, Eszterbauer, Marton, Cech et Székely, 2009, M. erythrophthalmi Molnár, Eszterbauer, Marton, Cech et Székely, 2009, M. gayerae Molnár, Marton, Eszterbauer et Székely, 2007, M. cyprinicola and M. miyairii Kudoa, 1919.…”

“…To explore the phylogenetic relationships of the present species with related myxobolids, 43 sequences were retrieved from GenBank and aligned using Clustal X 1.8 program (Thompson et al 1997) with defaulting setting. The data set for alignment consisted of the top BLAST search matches and representatives of neighbouring clades based on earlier analyses of myxobolids (Molnár et al 2006, Liu et al 2016a). The alignment was corrected manually using the alignment editor of MEGA6.0 software (Tamura et al 2013).…”

Morphological and molecular characterization of Myxobolus mucosus sp. n. (Myxosporea: Myxobolidae) with basifilamental sporulation in two cyprinid fishes, Rutilus rutilus (L.) and Leuciscus leuciscus (L.) in Russia

“…However, it is still ambiguous to what extent of sequence variation can be determined to be intraspecific or interspecific. Myxobolus dujardini was reported to have as much as 3.6 % intraspecific sequence variation (Molnár et al 2006), while Myxobolus honghuensis is 98.5 % similar to Myxobolus ampulicapsulatus (Liu et al 2012). Molecular markers with high resolution probably give better insight into the process of species differentiation of myxosporean parasites.…”

“…Thus, a comprehensive strategy including spore morphology, exact location of sporulation, tissue specificity, host specificity, and molecular data was widely thought to be essential for differentiation of the large number of species with morphological similarity. Additionally, some new Myxobolus species with specific habitat have been recently reported in roach in Hungary (Molnár et al 2006(Molnár et al , 2008(Molnár et al , 2010. To further correctly uncover the myxosporean diversity of freshwater fish in Finish Bay by applying the late taxonomic criteria, we performed a myxosporean fauna investigation of three consecutive years (2012)(2013)(2014).…”