Ceratomyxa gouletti n. sp. (Myxosporea: Ceratomyxidae), a parasite of the red scorpionfish Scorpaena scrofa (L.) from Tunisian waters

Ceratomyxa gouletti n. sp. is a new parasite described from the gallbladder of the red scorpionfish Scorpaena scrofa (Scorpaeniformes: Scorpaenidae) collected from La Goulette in the Northeast of Tunisia. The parasite develops disporic plasmodia, elliptical to ovoid in shape, measuring up to 33.1 ± 3.6 (28.0–38.2) μm in length and 12.5 ± 2.1 (11.3–14.0) μm in width. Mature spores are elongated transversely and crescent-shaped with rounded ends and unequal shell valves, measuring 8.1 ± 1.27 (7.2–9.0) μm in length and 32.0 ± 2.5 (27.0–38.2) μm in thickness. Sutural line is straight and visible between valves. Polar capsules are subspherical with 3.15 ± 0.63 (2.7–3.6) μm long and 1.9 ± 0.14 (1.8–2.0) μm wide. Posterior spore angle is slightly concave 160°–175°. Molecular analysis based on the small subunit 18S rDNA sequence shows that C. gouletti n. sp. is different from all other ceratomyxid species DNA sequences in GenBank. Phylogenetic trees clustered the new species with long-branching Ceratomyxa species, and it was closely related to the species Ceratomyxa longipes from two gadid fish hosts with 89% bootstrap support.