A note on the behaviour ofPatina pellucidain Britain and Norway

The behaviour of the gastropod, Patina pellucida, on Laminaria hyperborea has been investigated in the Isle of Man and near Bergen, western Norway. The animals first settle on the frond. In Britain they later migrate down the stipe and enter the holdfast where they create large cavities while in Norway they remain on the frond and the uppermost part of the stipe. This species probably causes considerable loss of plants due to weekening of the holdfast in one case and grazing of the frond and stipe in the second. The degree of infestation in different plant age-groups has been investigated in the Isle of Man.