Avoidance of dried biofilms on slate and algal surfaces by certain spirorbid and bryozoan larvae

The effect of aerial drying of biofilmed surfaces to simulate a tidal emersion upon the settlement preferences of spirorbid and bryozoan larvae was investigated using choice experiments with still water conditions carried out in the laboratory. Aerial drying of biofilmed slates and pieces of Fucus serratus for 1 h at 20°C negated their usual settlement-inducing properties to larvae of Spirorbis spirorbis, S. tridentatus and Flustrellidra hispida. Such larval settlement preference may contribute to observed variations in the natural distribution of these species in the intertidal.