The ciliate community of the Bay of Quinte, Lake Ontario was assessed over a six year period from 2003 – 2008. One eutrophic site in the upper bay (Belleville) and one more oligotrophic site in the lower bay (Conway), were included in the survey. Both sites contained a mixture of Haptoria, Strobilidium, Halteria, Strombidium, and Vorticella, although the relative proportions varied among sites resulting in different community structures. Ciliate biomass was found to be significantly higher at Belleville (mean: 100.2 ± 14.1 mg m^–3) compared to Conway (mean: 37.1 ± 3.5 mg m^–3), but could be explained by sudden pulses of Haptoria, primarily species of Mesodinium, which peaked as high as 678.1 mg m^–3. Canonical Correspondence Analysis showed a clustering of Halteria, Strobilidium, Tintinnina, Urotricha and Vorticella with surface temperature along with autotrophic picoplankton as a potential prey item. The results suggest that autotrophic picoplankton may be an important food resource for the ciliate community and that there is a strong seasonal gradient to community structure. Future research should be directed at understanding how ciliates influence the transfer of both primary and secondary production to higher trophic levels.

Aloricate ciliates are essential members of the pelagic microbial foodweb and are easy to identify in samples, yet the taxonomic database is insufficient and many species have yet to be described. Individuals from the Phylum Ciliophora Doflein, 1901, Order Choreotrichida Small and Lynn, 1985 were collected from the epilimnion (upper 20m) of Lake Ontario in the spring, summer and autumn of 1990 and 1991. They were fixed and silver-stained. Here we describe the morphospecies of five species from the genus Rimostrombidium Jankowski, 1978: Rimostrombidium kyoskota n.sp., Rimostrombidium pentagrammum n.sp., Rimostrombidium trioeumekes n.sp., Rimostrombidium paravelox Kahl, 1932 n.comb., Rimostrombidium brachykinetum Krainer, 1995 and one from the genus Pelagostrobilidium Petz et al., 1995: Pelagostrobilidium limnospirale n.sp. Increasing the taxonomic database allows for a more detailed monitoring of the biodiversity and energy transfer within a system, which in turn can better inform ecosystem management decisions.

Conchophthirus curtus is a scuticociliate found in the mantle cavity of unionid bivalve mussels; it is considered by most to be an endocommensal. It was previously redescribed and its morphogenesis has been carefully defined and evaluated. Conchophthirus stomatogenesis along with its enigmatic deep kinetosomal unit as compared with other scuticociliates, peniculines, and peritrichs suggested possible homologies and affinities. Thus, a comparison of Conchophthirus with common molecular markers to all other ciliates was a goal of this study. We collected Conchophthirus spp. in California from two unionid bivalve hosts: Anodonta californiensis in the Pit River and Lake Merced, and Margaritifera falcata from the Trinity River. The ciliates analyzed were predominantly C. curtus although other conchophthirids were present. The small subunit rRNA and the cytochrome c oxidase subunit 1 genes were sequenced. Phylogenetic analyses of these data were analyzed and maximum likelihood for the small submit rRNA dataset and neighbor-joining for the cytochrome c oxidase subunit 1 dataset. The cytochrome c oxidase subunit 1 sequences obtained from M. falcata populations were virtually identical. The analysis placed these sequences with 96% bootstrap support as sister to Dexiotricha sp. The small submit rRNA sequences obtained from populations from both hosts were almost identical, and they showed them to be sister, with 99% support to two unpublished sequences from Chinese populations of Conchophthirus cucumis and C. lamellidens, and sister to a Dexiotricha sp. These data and their analyses confirm Conchophthirus to be a scuticociliate, but not closely related to either philasterine or pleuronematine scuticociliates nor the peniculines or peritrichs. Further analysis awaits additional data. The North American distribution of Conchophthirus, niche analyses, and potential homologous structures are discussed as well as the use of these endocommensals as indicators of water quality and pollution.

Dinoflagellates can serve as predators or parasites of tintinnid ciliates. Known predators feed on the ciliate from outside the tintinnid lorica, while parasites either grow in the host cytoplasm or feed inside in the lorica while attached to the outside of the host cell. Here we report mixotrophic species of Scrippsiella that enter the lorica to consume the ciliate zooid of Helicostomella subulata from Denmark and multiple tintinnid species from Korea. We contrast morphology and life-history stages of these mixotrophic predators with dinokaryote parasites of tintinnids and address phylogenetic relationships based on rDNA sequences. Mixotrophic Scrippsiella species sometimes attack tintinnids that are simultaneously infected by syndinean dinoflagellates, complicating study of life histories and potentially leading to confusion about trophic status and taxonomy.

We reinvestigated Pycnothrix monocystoides Schubotz, 1908 from the intestine of the African Rock Hyrax (Procavia capensis) collected from Saudi Arabia, using protargol impregnation and electron microscopy. Pycnothrix is a unique, up to 5mm long intestinal ciliate with about two million cilia and many cytostomes (i.e. actual cytostome plus cytopharynx; polycytopharyngy) in the oral furrow (∼vestibulum) that extends on both sides of the cell. Both walls of the furrow are covered by adoral membranelle-like ciliary polymerizations. To the right of the furrow and the cytostomes there are small ciliary fields, very likely homologous to the “dorsal brush” found in free-living litostomateans. The molecular investigations show Pycnothrix as sister to Balantidium and endemic Australian intestinal ciliates, e.g. the genus Bandia. We propose that the common ancestor had both an oral furrow and a special ciliary field both similar to that found in Balantidium. The unique morphology (polycytopharyngy) and the rather distinct molecular separation suggest maintenance of the family status given by Poche (1913).

Ciliated protozoa are important components of the plankton of aquatic systems with ability to recycle nutrients and to link microbial food webs to metazoans. This is because they are numerous and have higher growth rates compared to other unicellular eukaryotes of similar size. Predation and competition are some of the factors that negatively affect their abundance and growth. Studies documenting the impact of predation by zooplankton on ciliates have been conducted in marine and freshwaters waters but are lacking in tropical waters especially soda lakes in Kenya. In this study, growth rates of planktonic ciliates were estimated in four soda lakes, Lakes Bogoria, Elmenteita, Simbi and Sonachi, using predator exclusion experiments. In the experiments, ciliate populations increased faster in incubations of lake water with the >40 µm fraction removed than in untreated controls. The difference in these rates was taken as an estimate of predation by zooplankton >40 µm (M_z), and ranged from 0.091 to 3.171 d^–1. Our best estimates of growth rates for particular ciliates abundant enough to derive estimates for ranged from 0.18 to 4.78 d^–1. When removing the >40 µm fraction did not result in increased numbers of ciliates relative to controls, we hypothesized that this was due to predators within the <40 µm fraction (M_c) and their release from zooplankton predators. We assessed and supported this hypothesis by looking at the production of ciliates in different feeding guilds. The significance of predation on ciliates to the food webs of soda lakes is discussed.