In the present study experiments were conducted to evaluate the toxic effects of monocrotophos on ciliate models Paramecium caudatum and Oxytricha fallax, which can be considered as ideal organisms for investigating water quality fluctuations and risk assessment of pesticides. Cell viability, cell morphology, cell behaviour and macronucleus tests were performed using to different concentrations...

Behavioral and electrophysiological experiments were made to examine the hypothesis that G-proteins modulate the voltage-dependent calcium channel in the marine ciliate Paramecium calkinsi. It was found that guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S), an analogue of GTP that binds to and activates G-proteins, increased the duration of backward swimming behavior in reversibly permeabilize...

Using para-nitrophenyl phosphate (pNPP) as a substrate for enzymatic activity, we sought to identify CaN in Paramecium. We isolated three different pNPP-phosphatases from the soluble fraction of Paramecium cells by anion-exchange and affinity column chromatographies. One, pNPP-phosphatase Peak I, is very similar to mammalian CaN. Divalent cation dependency, inhibition by calmodulin (CaM) antago...

Despite growing interest in ecological consequences of parasitism in food webs, relatively little is known about effects of parasites on long-term population dynamics of non-host species or about whether such effects are density or trait mediated. We studied a tri-trophic food chain comprised of (i) a bacterial basal resource (Serratia fonticola), (ii) an intermediate consumer (Paramecium cauda...

K(+)-selective ion channels (K(+) channels) have been found in bacteria, archaea, eucarya, and viruses. In Paramecium and other ciliates, K(+) currents play an essential role in cilia-based motility. We have retrieved and sequenced seven closely related Paramecium K(+)-channel gene (PAK) sequences by using previously reported fragments. An additional eight unique K(+)-channel sequences were ret...

In the ciliated protozoan Paramecium tetraurelia, Piwi-associated small RNAs are generated upon the elimination of tens of thousands of short transposon-derived DNA segments as part of development. These RNAs then target complementary DNA for elimination in a positive feedback process, contributing to germline defense and genome stability. In this work, we investigate the formation of these RNA...

Ectotherms generally demonstrate nonlinear changes in performance (e.g., movement speed, individual growth, population growth) as a function of temperature that are characterized by thermal performance curves (TPC). Predation risk elicits phenotypic and behavioral changes that likewise impact performance measures. We tested whether exposure to predation Orthocyclops modestus impacts the maximum...

Contrary to an earlier report suggesting clonal immortality in Paramecium caudatum, the clones of the same species in this study terminated inevitably with a maximal life-span of 658 fissions and showed, prior to clonal death, decreased fission rate, increased probability of the appearance of non-dividing or dead cells after cell division, and increased frequency of morphological abnormality an...

An analysis of swimming patterns in the ciliate Paramecium shows that the ability to swim preferentially upwards (negative gravitaxis) is primarily the result of upwardly curving trajectories. The trajectory characteristics are consistent with those produced by mechanical orientation. Cell profile measurements from microscope images suggest that the characteristic front-rear body asymmetry acco...

In parasites with mixed modes of transmission, ecological conditions may determine the relative importance of vertical and horizontal transmission for parasite fitness. This may lead to differential selection pressure on the efficiency of the two modes of transmission and on parasite virulence. In populations with high birth rates, increased opportunities for vertical transmission may select fo...