We propose that delayed predator-prey models may provide superficially acceptable predictions for spurious reasons. Through experimentation and modelling, we offer a new approach: using a model experimental predator-prey system (the ciliates Didinium and Paramecium), we determine the influence of past-prey abundance at a fixed delay (approx. one generation) on both functional and numerical resp...

PP63 (parafusin) is a 63 kDa phosphoprotein, which exists in at least two different isoforms. It is very rapidly (80 ms) dephosphorylated during triggered trichocyst exocytosis. This occurs selectively in exocytosis-competent Paramecium tetraurelia strains. At least two protein kinases isolated from Paramecium, casein kinase type II kinase and cGMP-dependent kinase, are able to phosphorylate th...

The behaviour of swimming Paramecium is markedly affected by hydrostatic pressure (50-200 atm, 1 atm = 101 325 Pa). To investigate whether pressure might alter behaviour by acting directly on specific ion channels that mediate the behavioural responses, we examined the effects of K+, Na+ and Ba2+ ions on swimming speed and the reversal response during pressurization and decompression. If pressu...

Paramecium tetraurelia is a unicellular organism that utilizes both axonemal and cytoplasmic dyneins. The highly conserved region containing the catalytic P-loop of the dynein heavy chain was amplified by RNA-directed polymerase chain reaction. Eight different P-loop-containing cDNA fragments were cloned. Southern hybridization analysis indicated that each fragment corresponds to a separate dyn...

We propose a qualitative physical model of galvanotaxis of Paramecium cells using a bottom-up approach to link the microscopic ciliary motion and the macroscopic behavior of the cells. From the characteristic pattern of ciliary motion called the Ludloff phenomenon, the torque that orients the cell toward the cathode is derived mathematically. Dynamical equations of motion are derived and their ...

Pattern regulation was investigated in the progeny of laterally fused cells of Paramecium tetraurelia. The immediate progeny of such fused cells (doublets) reveal two sets of cortical organelles arranged roughly symmetrically. Doublets tend to transform gradually into cells with only one set of organelles (singlets). At least two different and mutually exclusive pathways of doublet-to-singlet t...

The genetic effective population size (N(e)) of a species is an important parameter for understanding evolutionary dynamics because it mediates the relative effects of selection. However, because most N(e) estimates for unicellular organisms are derived either from taxa with poorly understood species boundaries or from host-restricted pathogens and most unicellular species have prominent phases...

1. Frequency polygons in which the number of observations at each temperature is reduced to a percentage basis while the time factor is represented on a logarithmic scale, indicate that the time required by Paramecium to swim a unit distance at different temperatures varies within definite limits which are constant above 15 degrees . Below 15 degrees the range of variability very possibly is no...

The relation of mortality and the proportion of progeny with reduced fission after autogamy to the clonal age in Paramecium aurelia was investigated. This relation is not linear but the proportion of defective progeny in creases stepwise. The observations are in agreement with those expected from the calculations of the number of deleterious mutations in the micronucleus.