Use of endocommensal molluscan ciliated protozoa as indicators of water quality and pollution in Illinois waters

Fifteen species of unionid bivalves from seventeen localities in Central Illinois were carefully examined for ciliate protozoan infections. Many ciliates appeared occasionally, but the thigmotrich ciliates Conchophthirus and Heterocinetopsis unionidarum appeared abundantly and consistently. New observations on the morphology of Conchophthirus and their ultimate effect upon speciation within the genus are to be developed further by the junior author. H. unionidarum was found abundantly at one location. Although Conchophthirus and Heterocinetopsis were the only thigmotrichs uncovered in this study, the isolation of Heterocinetopsis suggests that other thigmotrich ciliates may also be found in Illinois. The ciliates Conchophthirus and Heterocinetopsis were tested for their ability to react as very delicate indicators of water quality. This was accomplished by planting infected bivalves in areas of known pollution in the Salt Fork Vermilion River dra.ina.ge system. At intervals after planting, individuals were recovered and carefully examined for the relative abundance of Conchophthirus and Heterocinetopsis. The preliminary results suggest that Heterocinetopsis may be the most critical indicator of biological pollution currently available for Illinois waters.U.S. Department of the InteriorU.S. Geological SurveyOpe

Molecular Phylogeny and Evolutionary Relationships between the Ciliate Genera Peniculistoma and Mytilophilus (Peniculistomatidae, Pleuronematida)

Peniculistoma mytili and Mytilophilus pacificae are placed in the pleuronematid scuticociliate family Peniculistomatidae based on morphology and ecological preference for the mantle cavity of mytiloid bivalves. We tested this placement with sequences of the small subunit rRNA ( SSUrRNA) and cytochrome c oxidase subunit 1 ( cox1) genes. These species are very closely related sister taxa with no distinct genetic difference in the SSUrRNA sequence but about 21% genetic difference for cox1, supporting their placement together but separation as distinct taxa. Using infection frequencies, M. pacificae, like its sister species P. mytili, does not interact with Ancistrum spp., co-inhabitants of the mantle cavity. On the basis of these ecological similarities, the fossil record of host mussels, and features of morphology and stomatogenesis of these two ciliates, we argue that M. pacificae derived from a Peniculistoma-like ancestor after divergence of the two host mussels. Our phylogenetic analyses of pleuronematid ciliates includes the SSUrRNA gene sequence of Sulcigera comosa, a Histiobalantium-like ciliate from Lake Baikal. We conclude: ( i) that the pleuronematids are a monophyletic group; ( ii) that the genus Pleuronema is paraphyletic; and ( iii) that S. comosa is a Histiobalantium species. We transfer S. comosa to Histiobalantium and propose a new combination Histiobalantium comosa n. comb