The first report of two Sphaeromyxa species (Myxozoa: Bivalvulida) from the South China Sea: Sphaeromyxa scorpaena n. sp. from long-fingered scorpionfish (Scorpaenodes albaiensis) and Sphaeromyxa theraponi from tiger perch (Terapon jarbua).

Two myxosporean species of the genus Sphaeromyxa were isolated from the gallbladders of marine fish in the South China Sea. Sphaeromyxa scorpaena n. sp. was collected from Scorpaenodes albaiensis Evermann and Seale, 1907. The mature myxospores were arcuate-shaped with tapered to pointed ends, and a length of 14.1 ± 0.7 (13.8-15.1) μm and a width of 5.2 ± 0.3 (4.9-5.8) μm. The polar capsules (PCs) were pyriform with a length of 3.2 ± 0.2 (3.1-3.5) μm and a width of 1.6 ± 0.1 (1.4-1.8) μm, and containing ribbon-like polar filaments irregularly folded 1.5-2.5 turns. Molecular characteristics and phylogenetic analysis based on 18S rDNA as well as morphological comparison confirmed that S. scorpaena n. sp. was a previously undescribed species. Sphaeromyxa theraponi, isolated from Terapon jarbua Forsskål, 1775, was reported for the first time from the South China Sea. The mature myxospores were slightly arched, tapering to bluntly rounded ends, with a length of 17.3 ± 0.9 (15.5-19.4) μm and a width of 4.8 ± 0.3 (4.1-5.3) μm. A sporoplasm was situated in the space between PCs in the myxospore. The PCs were pyriform, which contained ribbon-like polar filaments irregularly folded by 2-3 turns, with a length of 7.0 ± 0.5 (5.8-8.1) μm and a width of 2.6 ± 0.2 (2.2-3.0) μm. Our morphological and phylogenetic analyses suggest that the pointed ends of S. scorpaena n. sp. might be a secondarily acquired characteristic rather than an ancestral trait.