Morphology and molecular phylogeny of Ortholinea mullusi sp. nov. (Myxozoa) in Mullus barbatus from the Black Sea

Synopsis of the species of Ortholinea Shulman, 1962 (Cnidaria: Myxosporea: Ortholineidae)

A synopsis of Ortholinea Shulman, 1962 (Cnidaria: Myxosporea: Ortholineidae) is presented and identifies 26 nominal species presently allocated within this genus. Species morphological and morphometric features, tissue tropism, type-host, and type-locality are provided from original descriptions. Data from subsequent redescriptions and reports is also given. Accession numbers to sequences deposited in GenBank are indicated when available, and the myxospores were redrawn based on original descriptions. The information gathered shows that Ortholinea infect a wide taxonomic variety of freshwater and marine fish. Nonetheless, the broad host specificity reported for several species is not fully supported by morphological descriptions and requires molecular corroboration. The members of this genus are coelozoic and mainly parasitize the urinary system, with few species occurring in the gallbladder. Ortholinea visakhapatnamensis is the only exception, being histozoic in the visceral peritoneum. Molecular data of the small subunit ribosomal RNA gene (SSU rDNA) is available for about one third of Ortholinea species, with genetic interspecific variation ranging between 1.65% and 29.1%. Phylogenetic analyses reveal Ortholinea to be polyphyletic, with available SSU rDNA sequences clustering within the subclades of the highly heterogenous freshwater urinary clade of the oligochaete-infecting lineage. The life cycles of two Ortholinea species have been clarified based on molecular inferences and identify triactinomyxon actinospores as counterparts, and marine oligochaetes of the family Naididae as permissive hosts to this genus.

New molecular evidence on the members of the genus Ortholinea (Cnidaria, Myxozoa) and the description of Ortholinea hamsiensis n. sp. infecting the urinary bladder of European anchovy Engraulis engrasicolus in the Black Sea

Members of the genus Ortholinea are among the worldwide distributed myxozoan parasites that mainly infect marine fish. In this study, a new myxosporean species, Ortholinea hamsiensis n. sp., was isolated from the urinary bladder of European anchovy Engraulis engrasicolus collected from the Sinop coasts of the Black Sea. The prevalence and density values of infection were 1.4% and 1–5 individuals in the field of view (1 + ), respectively. Mature myxospores are subspherical with slight tapering down to the less pronounced tip in the frontal view and subspherical in the sutural view. Myxospores measured 9.1 ± 0.25 (8.8–9.9) μm in length, 9.2 ± 0.11 (8.9–9.4) μm in thickness, and 8.4 ± 0.33 (8.2-9.1) μm in width. Two polar capsules equal in size measured 3.1 ± 0.11 (3.0–3.3) μm in length and 2.7 ± 0.11 (2.6–2.9) μm in width. The polar tubule had 3–4 coils. Along with morphological peculiarities, the results of the 18S rDNA also revealed it to be a new species for science compared to the other species of the genus. In this study, another myxosporean species O. gobiusi was also detected in round goby Neogobius melanostomus with a prevalence of infection value of 4.8% and a density of 1–5 individuals in the field of view (1 + ). The present study also provided the first data of 18S rDNA of O. gobiusi from N. melanostomus and type species of the genus O. divergens from Gobius niger and the phylogenetic relationships of these species with other Ortholinea species have been revealed.

Ortholinea nupchi n. sp. (Myxosporea: Ortholineidae) from the urinary bladder of the cultured olive flounder Paralichthys olivaceus, South Korea

A new myxosporean parasite, Ortholinea nupchi n. sp. (Myxozoa; Bivalvulida), was isolated from the urinary bladder of the olive flounder Paralichthys olivaceus cultured on Jeju Island, Korea. Mature spores were subspherical in the valvular and apical views and ellipsoidal in the sutural view. The spores measured 7.6 ± 0.5 μm in length, 6.7 ± 0.3 μm in thickness, and 7.3 ± 0.5 μm in width. Two pyriform polar capsules measured 3.2 ± 0.1 μm in length and 2.7 ± 0.1 μm in width and were located at the same level at the anterior half of the myxospores. The suture line was straight in the middle of the spores, and the surface ridges ranged between five and seven, forming an intricate pattern. The result of the 18S rDNA comparison showed ≤ 93.0% similarity with other Ortholinea species. The phylogenetic tree demonstrated that O. nupchi n. sp. was closest to O. auratae and clustered with oligochaete-infecting myxosporeans (OIM) having urinary system infection tropism. Based on the comparison of environmental and host factors in the phylogenetic groups of the OIM clade, we propose that the infection of O. nupchi n. sp. originated from marine oligochaetes.

Molecular and morphological description of Myxidium parvum (Cnidaria) from Salaria pavo (Blenniidae) in the Black Sea

Members of the predominantly coelozioc genus Myxidum Bütschli, 1882 with more than 232 species have been reported from a wide variety of marine and freshwater fish species worldwide. In this study, 25 specimens of peacock blenny, Salaria pavo, were collected from Sinop on the Turkish Black Sea coast. The gills, fins, skin, urinary bladder, gal bladder, kidney, liver, gonads and smooth muscle tissue of the collected samples were investigated for myxosporean parasites. Myxidium parvum Yurakhno, 1991 was the only myxosporean found in the gall bladder of host fishes. Based on spore morphology, M. parvum had mostly overlapping measurement data of original description in spore length and width, polar capsule length but differed slightly in width; however, they were within the ranges previously reported from other blenniid host fish species in the Black Sea. Moreover, in this study, molecular analysis of the 18S rDNA gene of M. parvum isolates from S. pavo was done for the first time and our M. parvum genotypes appeared as sister to Myxidium incurvatum within the "Lineage II" of the marine Myxidium clade.

Morphological and molecular descriptions of Sphaeromyxa sevastopoli (Cnidaria) from host fishes from Sinop on the Black Sea coast

Members of the genus Sphaeromyxa Thélohan, 1892 have been reported from a wide variety of fish species worldwide. In the present study, specimens of rusty blenny, Parablennius sanguinolentus, collected from Sinop on the Turkish Black Sea coast were investigated for myxosporean parasites by using both conventional and molecular methods. Sphaeromyxa sevastopoli Naidenova 1970 was the only myxosporean parasite found in the gall bladder of host fishes. The morphology peculiarities of obtained S. sevastopoli spores are in good agreement with those of original description and the morphometric data overlapped in spore length and width but differed in polar capsule length and width; however, they were within the ranges previously reported from 18 host fish species. Moreover, in the present study, molecular analysis of the 18S rDNA gene of S. sevastopoli isolate in our P. sanguinolentus as well as isolates from shore rockling Gaidropsarus mediterraneus and knout goby Mesogobius batrachocephalus which were previously morphologically identified and reported by Okkay and Özer (Acta Zool Bulg 72(1):123-130, 2020) was done for the first time and our three S. sevastopoli genotypes were allocated to the "balbianii" group which is characterized by straight or slightly curved and fusiform or ovoid spores with ovoid polar capsules.

Ortholinea scatophagi (Myxosporea: Ortholineidae), a novel myxosporean infecting the spotted scat, Scatophagus argus (Linnaeus 1766) from southwest coast of India

A new species of myxosporean, Ortholinea scatophagi n. sp. infecting the urinary bladder of the spotted scat, Scatophagus argus (Linnaeus 1766) is described. O. scatophagi n. sp. is characterized by spherical myxospores with a slightly flattened anterior end and equal spore valves with extra sutural ridges on its surface; measured 7.34 ± 0.67 μm in length, 6.90 ± 0.71 μm in width and 6.48 ± 0.37 μm in thickness. Two polar capsules, equal, spherical to oval in shape, arranged diametrically opposite and measured 2.59 ± 0.42 μm in length and 2.24 ± 0.35 μm in width. Polar filaments, 21.84 ± 2.86 μm long, with four to five coils. Scanning electron microscopy revealed the presence of extra sutural ridges on spore surface. Pansporoblasts spherical to irregular in shape, measured 31.08 ± 2.67 μm in length and 13.88 ± 5.40 μm in width; Monosporic, disporic and polysporic plasmodial stages were observed; plasmodia spherical or irregular in shape with granular cytoplasm containing refractile granules. The species was compared with 23 existing nominal species of Ortholinea, based on morphology and morphometry. Molecular analysis resulted in a 1773 bp long SSU rDNA sequence (GenBank accession number MN 310514). In phylogenetic analyses the present parasite clustered with other members of Ortholinea, under the freshwater urinary clade. Considering the morphologic, morphometric and molecular differences with previously described species of Ortholinea, and differences in host and geographic locations, the present species is treated as new and the name Ortholinea scatophagi n. sp.is proposed.