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

Abstract

Myxosporeans of the genus Ortholinea have a worldwide distribution and infect organs and tissues of exclusively marine fishes. Here we describe the morphological and molecular characteristics of Ortholinea mullusi sp. nov. parasitizing the urinary bladder and kidney tubules of red mullet Mullus barbatus collected from the coastal zone of Sinop in the Black Sea, Turkey. Polysporic plasmodia with immature spores were either elongate, 37.0 ± 4.5 SD (30-50) µm long and 45.0 ± 3.8 (40-55) µm wide, or were round, up to 100.0 µm in diameter. Mature, free spores were spherical in the frontal view and measured 9.3 ± 0.2 (9.0-9.7) µm in length, 8.7 ± 0.3 (8.2-9.3) µm in width and 7.7 ± 0.1 (7.5-7.9) µm in thickness. We observed 2 polar capsules of equal size, which measured 3.1 ± 0.1 (3.0-3.2) µm long by 2.5 ± 0.1 (2.4-2.6) µm wide, and the tips of the polar capsules were open towards the sutural line. The prevalence of infection by O. mullusi sp. nov. was 24.5%. Phylogenetic analysis based on nuclear small subunit ribosomal DNA (SSU rDNA) clearly suggested O. mullusi to be a new species, clustered within a lineage comprising O. labracis and O auratae. Pairwise nucleotide similarities and DNA distance values between O. mullusi sp. nov. and sister Ortholinea species also supported this suggestion.

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

“…Myxospore dimensions of the new species are smaller than those of O. orientalis from navaga Eleginus gracilis (Tilesius, 1810) and Eleginus nawaga (Walbaum, 1792) but larger than those of O. orientalis from Atlantic herring Clupea harengus Linnaeus, 1758, Pacific herring, Clupea pallasi Valenciennes, 1847, Alaska Pollock, Gadus chalcogrammus Pallas, 1814, red mullet, Mullus barbatus ponticus Essipov, 1927, Black Sea shad, Alosa tanaica (Grimm, 1901) (Shulman and Shulman-Albova, 1953 ; Aseeva, 2000 ; Karlsbakk and Køie, 2011 ; Özer et al ., 2015 a ). The polar capsules of the new species are larger than those of O. orientalis from C. pallasii and E. nawaga , O. labracis from the European seabass, Dicentrarchus labrax (Linnaeus, 1758), O. scatophagi from the spotted scat, Scatophagus argus (Linnaeus, 1766) but, smaller than those of O. mullusi from M. barbatus ponticus, O. auratae from the gilthead seabream, Sparus aurata (Linnaeus, 1758), O. alata from the northern butterflyfish, Chaetodon rainfordi McCulloch, 1923, and O. striateculus from silver fish, Leptatherina presbyteroides (Richardson, 1843) (Shulman and Shulman-Albova, 1953 ; Kent and Moser, 1990 ; Su and White, 1994 ; Özer et al ., 2015 a ; Rangel et al ., 2017 ; Gürkanlı et al ., 2018 ; Chandran et al ., 2020 ). Ortholinea saudii from marbled spinefoot Siganus rivulatus (Abdel-Baki et al ., 2015 ) own too large polar capsules and myxospores compared to the new species in the present study.…”

“…Ortholinea (Shulman, 1962 ), the target myxozoan genus in this study, is composed of coelozoic 26 binominal parasite species that infect mainly the urinary bladder of mostly marine and rarely freshwater fishes (Lom and Dyková, 2006 ; Shin et al ., 2023 ). Despite its limited biological diversity when compared with some other myxosporean genera such as Myxobolus , Myxidium, etc., reported species from fishes of this genus reveal a worldwide distribution (Lom and Dyková, 1992 ; Rangel et al ., 2014 , 2015 , 2017 ; Gürkanlı et al ., 2018 ; Shin et al ., 2023 ). Concordant with this data, 4 Ortholinea species ( O. divergens , O. gobiusi , O. orientalis, O. mullusi ) have been reported from the Black Sea coasts of Türkiye thus far (Özer et al ., 2015 a , 2015 b ; Gürkanlı et al ., 2018 ).…”

“…Myxozoans are the cnidarian parasites that have been reported from fish inhabiting freshwater, brackish water and marine environments (Lom and Dyková, 2006 ; Gürkanlı et al ., 2018 ; Okkay and Özer, 2020 ). Description of myxozoan parasites is mainly based on myxospore morphology and according to this traditional criteria, species of the genus Ortholinea Shulman, 1962 have spherical or subspherical myxospores that are lightly flattened or tapered posterior parallel to the sutural plane, containing 2 polar capsules, subspherical or pyriform, and some species have surface stripes (Lom and Dyková, 2006 ).…”

“…Ortholinea is probably a genus known to have ancestors reviving marine habitats and it has recently been transferred from Ortholineidae to Myxobilatidae due to phylogenetic proximity (Karlsbakk et al ., 2017 ). This genus is represented by 26 species worldwide including 4 species that have been reported from marine fishes in the Black Sea coasts of Türkiye (Lom and Dyková, 1992 ; Karlsbakk, 2001 , Rangel et al ., 2014 , 2015 , 2017 ; Özer et al ., 2015 a , 2015 b ; Gürkanlı et al ., 2018 ; Shin et al ., 2023 ). Most of the Ortholinea species have been generally reported in the urinary bladder, but rarely in the kidney, gallbladder, and gill tissues of their host fishes (Rangel et al ., 2014 , 2015 , 2017 ; Gürkanlı et al ., 2018 ).…”

“…This genus is represented by 26 species worldwide including 4 species that have been reported from marine fishes in the Black Sea coasts of Türkiye (Lom and Dyková, 1992 ; Karlsbakk, 2001 , Rangel et al ., 2014 , 2015 , 2017 ; Özer et al ., 2015 a , 2015 b ; Gürkanlı et al ., 2018 ; Shin et al ., 2023 ). Most of the Ortholinea species have been generally reported in the urinary bladder, but rarely in the kidney, gallbladder, and gill tissues of their host fishes (Rangel et al ., 2014 , 2015 , 2017 ; Gürkanlı et al ., 2018 ). In a recent study, Okkay and Özer ( 2020 ), based on morphological criteria, reported Ortholinea orientalis from the urinary bladder of European anchovy, Engraulis encrasicolus (Linnaeus, 1758) and Pontic shad, Alosa immaculata Bennett, 1835, Ortholinea divergens from the kidney of grey wrasse, Symphodus cinereus (Bonnatterre, 1788) and Ortholinea sp.…”