Together with the influence of abiotic environmental factors, mollusks sustain the influence of species in communities. Mollusca is the largest marine phylum, comprising about 23% of all the named marine organisms. This book presents current research in the study of the morphology, behaviour and ecology of mollusks. Topics discussed include the topic and trophic relationships of marine bivalves with their epi- and endobionts; chemical neuroanatomy of the cholinergic neurons in the cephalopod octopus and gastropod limax; biological and ecological aspects of the larvae of the Dreissena blanci mollusk; paleontological data on the possibility of precambrian existence of mollusks; the problem of geographical variation in freshwater gastropods and benthic mollusks of the Middle Parana River in Argentina.