THE USE OF MUCOUS TRAILS BY INTERTIDAL LIMPETS TO ENHANCE FOOD RESOURCES

The mucous trails secreted by certain species of intertidal limpets serve as adhesive traps for the microalgae that are their primary food resources. The mucous trails of two solitary homing limpets, Lottia gigantea and Collisella scabra, also stimulate the growth of microalgae. In contrast, the mucous trails of an aggregating limpet, Collisella digitalis, and the carnivorous dog whelk, Nucella emarginata, do not stimulate microalgal growth. These results may be explained by differences in the behavior of these gastropod species. Homing species can capitalize on the production of a food enhancing mucus because they have restricted home ranges and retrace their own mucous trails. The persistence time of mucus in the field varied with gastropod species, mucus type (i.e., mucus produced by moving or stationary limpets), and tidal height. Field studies suggest mucous trails can, but may not always, persist long enough to allow algal enhancement. Biochemical analyses suggest that the ability of mucous trails to trap microalgae adhesively is correlated with carbohydrate content. The ability of mucous trails to stimulate microalgal growth is correlated with higher total organic content of mucous secretions and an ability to stimulate bacterial growth. A bacterial film may be important in the stimulation effect.