A novel myxosporean parasite Myxobolus klamathellus n. sp. (Cnidaria: Myxosporea) from native blue chub (Gila coerulea) in Klamath Lake, Oregon.

Blue chub, Gila coerulea Girard, 1856 is a freshwater cyprinid fish native to inland drainages of western North America. It has not previously been recorded as a host of any myxosporean parasite (Cnidaria: Myxosporea), despite myxosporeans being cosmopolitan in freshwater and marine fishes worldwide and sympatric with this host. Herein, we describe a novel myxosporean from subcutaneous cysts in native blue chub from Klamath Lake, Oregon. Myxospores were consistent with genus Myxobolus, being obovoid but compressed in thickness, length 14.3 ± 0.4 (13-15) µm, width 9.7 ± 0.4 (9-10) µm, thickness 7.7 ± 0.3 (7-8) µm; two polar capsules ovoid slightly dissimilar in size, length 6.4 ± 0.4 (6-7) µm, width 3.8 ± 0.3 (3-4) µm, with four (3-5) turns of the polar filament (tubule); capsule openings apical, one in each valve cell. The small subunit ribosomal DNA sequence was up to 97 % similar to Myxobolus spp. from other cyprinids from North America and Europe. Given the novel host, unique myxospore morphometrics, and DNA sequence, we describe this as Myxobolus klamathellus n. sp.

Sphaerospora sensu stricto: taxonomy, diversity and evolution of a unique lineage of myxosporeans (Myxozoa).

Myxosporeans (Myxozoa) are eukaryotic parasites, primarily of fish, whose classification is in a state of flux as taxonomists attempt to synthesize the traditional morphology-based system with emerging DNA sequence-based phylogenies. The genus Sphaerospora Thélohan, 1892, which includes pathogenic species that cause significant impacts on fisheries and aquaculture, is one of the most polyphyletic taxa and exemplifies the current challenges facing myxozoan taxonomists. The type species, S. elegans, clusters within the Sphaerospora sensu stricto clade, members of which share similar tissue tropism and long insertions in their variable rRNA gene regions. However, other morphologically similar sphaerosporids lie in different branches of myxozoan phylogenetic trees. Herein, we significantly extend taxonomic sampling of sphaerosporids with SSU+LSU rDNA and EF-2 sequence data for 12 taxa including three representatives of the morphologically similar genus Polysporoplasma Sitjà-Bobadilla et Álvarez-Pellitero, 1995. These taxa were sampled from different vertebrate host groups, biogeographic realms and environments. Our phylogenetic analyses and statistical tests of single and concatenated datasets revealed Sphaerospora s. s. as a strongly supported monophyletic lineage, that clustered sister to the whole myxosporean clade (freshwater+marine lineages). Generally, Sphaerospora s. s. rDNA sequences (up to 3.7 kb) are the longest of all myxozoans and indeed metazoans. The sphaerosporid clade has two lineages, which have specific morphological, biological and sequence traits. Lineage A taxa (marine Sphaerospora spp.) have a single binucleate sporoplasm and shorter AT-rich rDNA inserts. Lineage B taxa (freshwater/brackish Sphaerospora spp.+marine/brackish Polysporoplasma spp.) have 2-12 uninucleate sporoplasms and longer GC-rich rDNA inserts. Lineage B has four subclades that correlate with host group and habitat; all Polysporoplasma species, including the type species, cluster together in one of these subclades. We thus suppress the genus Polysporoplasma and the family Polysporoplasmidae and emend the generic diagnosis of the genus Sphaerospora. The combination of morphological, biological and DNA sequence data applied in this study helped to elucidate an important part of the taxonomic puzzle within the phylum Myxozoa.

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.