Planktonic ciliates occasionally form brief rapid increases in numbers (blooms) that can be trophically important. Although model simulations and mesocosm studies indicate that blooms occur over 10 to 20 days, field data are rarely suffi ciently detailed to reveal their occurrence and demise. Our data (collected over 57 weeks across a coastal lagoon) offer insights into the population dynamics of a single species, place these in the context of the entire ciliate assemblage, and provide guidance on what should continue to be examined. Specifically, to evaluate population dynamics we examine two species of Cyrtostrombidium, characterise temporal and spatial variation of their abundance, and relate these to abiotic phenomena and biological factors. This is also the first report of Cyrtostrombidium in a tropical coastal lagoon. Collectively our analysis reveals key aspects of the dynamics of this genus: 1) small-scale peaks in abundance are ~30 m in size and can persist for ~10–30 days, reaching a maximum of 100 cells ml–1; 2) these increases are driven by biotic factors (revealed through autocorrelation analysis); 3) long-term trends are driven by the shift between dry and rainy seasons and by the periods of isolation of lagoon from the sea (revealed through multiple regression analysis); 4) blooms may at times control primary production; 5) conjugation, an ecologically important event, may be associated with blooms (at times 9% of population was conjugating); and 6) dinoflagellate parasitism, poorly described in oligotrichs, is potentially important in population demise. These results both reflect on how ciliates may behave in short-term events and should encourage the continued need for detailed observations of field samples at a high taxonomic resolution.
 

Ciliate communities in open waters of the meso-eutrophic Neva Estuary (the Baltic Sea) were studied in summer 2010. Abundance and biomass of ciliates were surprisingly low (0.03–1.9 ind ml–1 and 0.04–2.4 × 10–3 μg C ml–1), especially in samples with high detritus content. During this study we detected four ciliate species which are new for the Baltic Sea. Mixotrophic ciliates dominated at the majority of stations (28–67% of overall ciliate numbers). Their contribution was significantly higher in the outfall area and northern part of the Neva Estuary (Resort District), where total density of ciliates was low. Medium-sized ciliates (30–60 μm) were the most diverse and abundant (average contribution 59% of total abundance). The two parts of the estuary, separated from each other by a storm-surge barrier, differed slightly in their community structure (p < 0.05) but did not significantly differ in ciliate numbers and biomass values.
 

The present work investigates the living morphology and infraciliature of three marine cyrtophorid ciliates, which were isolated from Qingdao, China. Compared with its congeners, Orthotrochilia sinica spec. nov. can be distinguished by a combination of features: body slender and elliptical in outline, size about 50–60 × 20–25 μm in vivo, 18–21 somatic kineties, the length of the left perioral kinety treble the length of the right one, two ventrally located contractile vacuoles on the right side, and 25–32 nematodesmal rods. Based on current observations and the previous description, the diagnosis of Trochilioides tenuis (Deroux, 1976) Chen et al. 2011 is improved: cell size 30–40 × 20–35 μm in vivo, oval shaped in outline; consistently three right kineties, four left kineties and seven postoral kineties; a single contractile vacuole; marine habitat. A second species of Trochilioides, T. recta (Kahl, 1923) Chen et al. 2011 is re-described based on a Chinese population. Furthermore, a key to the identification of species of the genus Trochilioides whose infraciliature data are available is supplied, and Chlamydonyx trivialis (Fenchel, 1965) comb. nov. [basionym: Trochilioides trivialis Fenchel, 1965] is suggested.

Living observation and silver impregnation methods were used to investigate the morphology and infraciliature of three Frontonia ciliates (F. guangdongensis spec. nov., F. ocularis Bullington, 1939 and F. schaefferi Bullington, 1939) that were isolated from coastal waters of the South China Sea. Frontonia guangdongensis spec. nov. may be recognized by the combination of the following characteristics: cells about 160 × 35 μm in vivo; elongated body with right margin depressed in anterior third; length to width ratio 4:1 to 5:1; three or four vestibular and four or five postoral kineties; peniculi 1 and 2 each with four rows of kineties, peniculus 3 with two rows; one contractile vacuole in mid-body region right of cell median; brackish water habitat. A key based on morphological data for fourteen marine or brackish water Frontonia species found in China is also provided. In addition, the small subunit (SSU) rDNA gene was sequenced for F. ocularis Bullington, 1939. Our phylogenetic analyses support the contention that the genus Frontonia is not monophyletic.

n Colpoda cucullus, the signaling pathways for encystment induction involving protein phosphorylation have been believed to be triggered by an increase in the intracellular Ca2+ concentration promoted by cell-to-cell mechanical contact due to overpopulation. By means of fura 2 ratiometry, the present study showed that the intracellular Ca2+ concentration was actually elevated when vegetative cells were induced to encyst by being suspended at a high cell density in the presence of external free Ca2+ and suppressed by chelating external Ca2+. This result strongly suggests that an increase in the intracellular Ca2+ concentration caused by an inflow of Ca2+ promoted by cell-tocell mechanical contact due to overpopulation enhances the rate of encystation in Colpoda cucullus.