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. 2020 Apr;147(4):448-464.
doi: 10.1017/S0031182019001793. Epub 2019 Dec 26.

Phylogenetic characterisation of seven Unicapsula spp. (Myxozoa: Myxosporea: Multivalvulida) from commercial fish in southern China and Japan

Ying-Chun Li  1 , Souhei Tamemasa  2 , Jin-Yong Zhang  3 , Hiroshi Sato  2
Affiliations

Phylogenetic characterisation of seven Unicapsula spp. (Myxozoa: Myxosporea: Multivalvulida) from commercial fish in southern China and Japan

Ying-Chun Li et al. Parasitology. 2020 Apr.

Abstract

The myxozoan genus Unicapsula Davis, 1924 (Myxosporea: Multivalvulida: Trilosporidae) is characterized as having one functional polar capsule (PC) and two rudimentary PCs in a three-valved myxospore. The plasmodia of Unicapsula spp. grow either in the myofibres or in the gills, oesophageal walls and urinary organs of marine fish. Few studies have investigated the taxonomy of Unicapsula spp. including the type species Unicapsula muscularis. Accordingly, the taxonomy of the genus was explored in the present study by using 15 new isolates of seven Unicapsula spp. (U. muscularis, U. galeata, U. andersenae, U. pyramidata, U. pflugfelderi, and two new species) that had formed pseudocysts in the trunk myofibres of commercial fish collected in southern China and Japan from November 2015 to January 2019. Two new species Unicapsula trigona n. sp., and Unicapsula motomurai n. sp. exhibited unique myxospore morphologies (semi-triangular and spherical myxospores, respectively) and 18S and 28S rDNA sequences that were distinct from those of the other Unicapsula spp. Phylogenetic analysis of the 18S and 28S rDNA sequences confirmed the monophyletic status of Unicapsula.

Keywords: Integrated taxonomy; Myxozoa; Unicapsula; Unicapsula motomurai n. sp.; Unicapsula trigona n. sp.; new host record; rDNA.

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Figures

Fig. 1.
Fig. 1.
Microscopic view of myxospores of Unicapsula spp. collected in the present study. (A–F) Unicapsula andersenae (A, isolate Li1-1; B, Li1-6; C, Li4-1; D, Li3-4; E, Li4-2; and F, Li1-9); (G) Unicapsula pyramidata (Li3-3); (H–J) Unicapsula galeata (H, Li1-3; I, Li2-3; and J, Li2-4); (K) Unicapsula muscularis (Aburakarei); (L) Unicapsula pflugfelderi (Li2-2); (M) Unicapsula motomurai n. sp. (Li2-1); and (N) Unicapsula trigona n. sp. (Itoyoridai). All photographs at the same magnification (scale bar in N).
Fig. 2.
Fig. 2.
Stylized diagrams of Unicapsula spp. collected in the present study. (A) Unicapsula andersenae: (B) Unicapsula pyramidata; (C) Unicapsula galeata; (D) Unicapsula muscularis; (E) Unicapsula pflugfelderi; (F) Unicapsula motomurai n. sp.; and (G) Unicapsula trigona n. sp. Unicapsula spores consist of three shell valves with one prominent PC (pPC) and two rudimentary PCs (rPC) as examples are shown in (A). Unicapsula pyramidata myxospores have caudal filamentous appendages (CFA).
Fig. 3.
Fig. 3.
Microscopic view of myxospores of Unicapsula muscularis (isolate Aburakarei) collected in the present study.
Fig. 4.
Fig. 4.
Microscopic view of myxospores of Unicapsula motomurai n. sp. (isolate Li2-1) collected in the present study.
Fig. 5.
Fig. 5.
Microscopic view of myxospores of Unicapsula trigona n. sp. (Itoyoridai) collected in the present study.
Fig. 6.
Fig. 6.
Maximum likelihood phylogenetic tree of 18S rDNA sequence (A: 722 characters, and B: 1621 characters) from Unicapsula spp. Each species name is followed by the name of its fish host, the sea [country] from which it was collected and DDBJ/EMBL/GenBank accession number in parentheses. Abbreviation of sea names: AS, Arabian Sea; BS, Bering Sea; CS, Coral Sea around Australia; EAO, East Atlantic Ocean; ISJ, Inland Sea of Japan; JS, Japan Sea; MS, Mediterranean Sea; PS, Philippine Sea off Kochi, Japan; and SC, South China Sea. Abbreviation of country names: AU, Australia; CN, People's Republic of China; ES, Spain; JP, Japan; OM, Oman; US, United States of America; and VN, Vietnam.
Fig. 7.
Fig. 7.
Maximum likelihood phylogenetic tree of 28S rDNA sequence (A: 540 characters, and B: 2156 characters) from Unicapsula spp. Labelling of each isolate and abbreviations of sea and country names are similar to those described in the legend for Fig. 6.
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