Abstract
The feeding behaviour of a small herbivorous gastropod, Homalopoma amussitatum was observed to test five sesquiterpenoids, i.e. zonarol, isozonarol, chromazonarol, zonarone and isozonarone, extracted from the brown alga Dictyopteris undulata, and phlorotannins from the two brown algae, Eisenia bicyclis and Ecklonia stolonifera. The experiments were conducted with the newly designed and developed experimental tank and time-serial photographic recording system. The snails showed strong time-lasting deterrent reactions to all the extracts whose activities appeared to be different from one another. In order to understand the community organization through the marine plant-herbivore interactions, the importance of chemical defense against small herbivores was discussed, and quantitative measurements of feeding deterrents for each herbivore concerned were recommended.
