A new species of Sphaeromyxa (Myxosporea: Sphaeromyxina: Sphaeromyxidae) in devil firefish, Pterois miles (Scorpaenidae), from the northern Red Sea: morphology, ultrastructure, and phylogeny.

Sphaeromyxa zaharoni n. sp. (Myxosporea) is described from the gallbladder of devil firefish, Pterois miles (Scorpaenidae), from coral reefs of the Gulf of Eilat, Israel, northern Red Sea. The parasite was found also in bearded scorpionfish, Scorpaenopsis barbata, from the same area. This is the first report on Sphaeromyxa sp. from this zoogeographical region. The plasmodia are amoeboid when young, becoming disc-shaped and elongated when mature. In paraffin sections, the plasmodium periphery appears as a finely granulated, strongly eosinophilic layer with an intricate surface membrane network. Sphaeromyxa zaharoni n. sp. is polysporous, disporoblastic, and has asynchronous sporogenesis. The mature spore is elongated and fusiform, has delicately ridged valves, and contains a single, binucleated sporoplasm. In valvular view, the tips are truncated. The mean spore size is length 14.5 microm, width 4.8 microm, and polar capsule 4.8 x 3.4 microm. The 2 equally sized ovoid polar capsules are positioned at opposite ends of the spore, each containing a filament loosely folded in 2 loops. The fine structure of the sporoblast and spore corresponded with previously studied Sphaeromyxa species. According to small-subunit ribosomal DNA gene sequence analysis, S. zaharoni n. sp. is most closely related to 2 Myxidium spp. The close phylogenetic relatedness of Sphaeromyxa and Myxidium and similar spore morphology raises the question whether these 2 genera should be maintained in separate families and suborders.