Interaction of two myxozoan parasites from naked goby Gobiosoma bosc, in Lake Pontchartrain, Louisiana.

During a parasitological survey of naked gobies ( Gobiosoma bosc ) in Lake Pontchartrain, Louisiana, U.S.A., 2 myxozoan parasites were found infecting the gall bladders of 84 of 90 fish. Parasite plasmodia of each were morphologically distinct; plasmodia bearing Ellipsomyxa-like spores were elongate and fusiform (1,126 by 403 μm), and those bearing Sphaeromyxa-like spores were large and discoid (1,400 μm diameter). Neither parasite conformed to any described species of myxozoan, and both are described here. Sphaeromyxa kenti n. sp. bears boomerang-shaped spores ranging 17.5-19.8 μm long by 3.8-5.2 μm wide. Two unequal sized polar capsules contain ribbon-like polar filaments characteristic of this genus. Ellipsomyxa adlardi n. sp. bears ovoid spores 11.3-14.4 by 7.1-8.8 μm, with 2 rounded polar capsules oriented in opposite directions relative to the longitudinal plane of the spore. Phylogenetically both species cluster with sequenced members of their respective genera. Plasmodia of E. adlardi n. sp. were encountered in 72.2% of gobies examined, and S. kenti n. sp. in 25.6%. Overall, 6.7% of animals were uninfected, and only 4.4% of the 90 fish examined were infected with both species. The observed co-occurrence was lower than expected by chance, strongly suggestive of an interaction between these species.