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.

一种新的粘孢子寄生虫，Ortholinea nupchi n。sp。(Myxozoa; Bivalvulida)，是从韩国济州岛养殖的橄榄比目鱼Paralichthys olivaceus的膀胱中分离出来的。成熟的孢子在瓣膜和顶端视图中呈亚球形，在缝合视图中呈椭圆形。孢子的长度为 7.6 ± 0.5 μm，厚度为 6.7 ± 0.3 μm，宽度为 7.3 ± 0.5 μm。两个梨形极性胶囊长 3.2 ± 0.1 μm，宽 2.7 ± 0.1 μm，位于粘孢子前半部分的同一水平。孢子中间的缝合线笔直，表面有五到七条脊线，形成错综复杂的图案。18S rDNA 比对结果显示与其他邻线亚目相似度≤ 93.0%物种。系统发育树表明O. nupchi n。sp。最接近O. auratae并且与具有泌尿系统感染趋向性的寡毛类感染粘孢子虫（OIM）聚集在一起。基于 OIM 进化枝系统发育群中环境和宿主因素的比较，我们提出O. nupchi n的感染。sp。起源于海洋寡毛纲。