Untersuchungen zur lichtinduzierten Chromatophorenverlagerung beiFucus vesiculosus

Light-induced transmission changes, measured microphotometrically in the brown algaFucus vesiculosus, are mainly the result of chromatophore displacements. Dose-response curves, as well as observations by microscope, have shown that the typical low-intensity arrangement occurs at 1 000 lux and the complete high intensity arrangement at 20 000 lux. The arrangements of the chromatophores — as well as their shapes — in dim light, strong light and darkness have been investigated. The chromatophore arrangements are different in the epidermal, cortical and medullary cells. In dim light the chromatophores are relatively large. The chromatophores of the epidermis are placed in the plasma layer of the inner cell halves. In the cortical and medullary cells the chromatophores occupy mainly the cell walls facing the light. In strong light the chromatophores are shorter and tend to become spherical. In the epidermis facing the light they move into the basal part of the cells, in the cortical and medullary cells they move to the center of the cell surrounding the nucleus. After some days of darkness the chromatophores of the epidermal cells occupy the inner periclinal and 2/3 of the anticlinal cell walls. In the cortical and medullary cells they are evenly distributed in the cytoplasmic layer at the wall. Obviously, the transmission changes measured are mainly due to chromatophore displacements in the cortical cells. Changes in shape and size play a minor role.