GENETIC VARIATION AND COVARIATION FOR CHARACTERISTICS ASSOCIATED WITH CADMIUM TOLERANCE IN NATURAL POPULATIONS OF THE SPRINGTAIL ORCHESELLA CINCTA (L.).

Heavy metals can be strong and stable directional selective agents for metal-exposed populations. Genetic variation for the metal-tolerance characteristic "cadmium excretion efficiency" was studied in populations of the collembolan Orchesella cincta from a reference- and a metal-contaminated forest soil. Previously it has been shown that "excretion efficiency" influences tolerance through midgut-mediated immobilization and excretion of toxic metal ions, and that an increased mean excretion efficiency is present in animals inhabiting metal-contaminated litter.

The role of food in the population dynamics of Orchesella cincta (Linné) (Collembola).

The feeding activity of the collembolan species Orchesella cincta (Linné) was studied in the laboratory and in the field. In the laboratory it was shown that at any one time only about 50-60% of the animals were feeding; the remainder were occupied with molting activities. Most of the time similar values were obtained in the field but during winter and during dry summer periods high percentages of empty guts could be demonstrated, indicating an absence or inaccessability of food.

Activity-stimulating phenomena caused by field-disturbance in the use of pitfall-traps.

The influence of several mechanical field disturbances, when using pitfall-traps for activity determinations, is analysed. The disturbances result in higher catches of surface-dwelling Collembola; the animals being stimulated to higher locomotory activity.The disturbance by walking in the field results in a multiple of the control catch.