0000000000406953
AUTHOR
Katja Löytynoja
Environmental noise and population dynamics of the ciliated protozoa Tetrahymena thermophila in aquatic microcosms
Population theory predicts that the reddened environmental noise, especially in combination with high population growth rate, reddens population dynamics, increases population variability and strengthens environment–population correlation. We tested these predictions with axenic populations of ciliated protozoa Tetrahymena thermophila. Populations with low and high growth rate were cultured in a stable environment, and in environments with sublethal temperature fluctuations that had blue, white and red spectra (i.e. negatively autocorrelated, uncorrelated, or positively autocorrelated, respectively). Population size and biomass of individuals were determined at 3-h intervals for 18 days. Dy…
Measured immunocompetence relates to the proportion of dead parasites in a wild roach population
Summary 1. Although various methods are used to measure immunocompetence, their relationship with the actual parasite clearance or parasite load is seldom demonstrated in natural systems. 2. We combined nine measures of immune function using principal component analysis (PCA), and examined the relationship of the collective measures with (i) the proportion of parasites killed by the host, (ii) the burden of several parasite species and (iii) a viral disease in a wild population of the roach, Rutilus rutilus. We also studied if these variables were associated with the concentration of steroids (testosterone and oestradiol). 3. Most significant correlations between the loads of ecto- and gill…