This book collects all the lectures presented during the NATO Advanced Study Institute on "Photoreception and Sensory Transduction in Aneura1 Organisms," held in Villa Le Pianore (Versi1ia, Italy), September 3-14, 1979. In order to publish the lectures in the shortest possible time, we had to make the decision not to include the free communications, the informal seminars, and the panel discussions, notwithstanding their very high scientific level and interest. Only the final panel discussion has been summarized by Prof. W. Haupt (whose effort we gratefully acknowledge), because it gives a comprehensive view of the state of the art in this field. The ASI was intended to be a high-level course, characterized by an interdisciplinary approach to the problem of photoreception and photosensory physiology in aneural organisms, bringing together scientists from different fields and specializations. We hope that these characteristics are reflected in the content of the book, which is meant to be both an advanced textbook for researchers and students entering the field and a critical overview of the problems of photosensory transduction in aneura1 organisms. The topics pre sented range from a phenomenological description of the different photomotile responses in various microorganisms to a discussion of the molecular processes involved in the primary events of photo reception as well as in the subsequent steps of the transduction chain."

The main purpose of this book is to unify approaches and ideas in the field of aneural sensory transduction. This field has recently come to the attention of several research groups in various disciplines, and their number seems to be growing. Unfortunately, because of the diverse scientific backgrounds of the researchers in the field, the apparent heterogeneity of experimental techniques (i. e., behavioral response analysis, sophisticated biochemical and genetic manipulations, conventional and pulsed laser spectroscopy) and theoretical approaches may be discouraging, for both the experienced worker and the new comer. Actually, this heterogeneity is more apparent than real, and unifying concepts, approaches, and ideas already exist, particularly with respect to all the questions concerning the role of membranes and their properties (such as ion permeability, electric potentials, and active transport) in the various steps of sensory perception and transduction processes. It is currently accepted that most, if not all, the fundamental facts in molecular sensory physiology of aneural organisms, be they chemosensory, photosensory, or geosensory, can ultimately be understood in terms of a few basic ideas. Each chapter of this book emphasizes and clarifies the role of mem brane properties and phenomena in the particular sensory response examined. Of course, in some cases, this task has been rather complex because of the limited amount of experimental data clearly supporting a membrane-based model of sensory transduction."

This book is based on the lectures given at the NATO Advanced Study Institute on "Sensory Perception and Transduction in Aneural Organisms" held in Volterra (Pisa. Italy) from the third to the fourteenth of September. 1984. The Advanced Study Institute was planned as a high level course dealing with several aspects and problems of sensory perception and transduction of diverse environmental stimuli in aneural organisms. Scientists from different fields and cultural backgrounds were present at the meeting. both as lecturers and as students. The lectures and the discussions that followed represented a well integrated interdisci plinary approach to the questions considered. At the end of the Advanced Study Institute course. it was quite clear that. notwith standing the apparent heterogeneity of the topics dealt with. unifying concepts and ideas already existed, among the most important being the role of membranes and their physicochemical properties. All this should be reflected in the content of this book. We gratefully acknowledge the financial sponsorship of the Scientific Affairs Division of NATO (Brussels), that made both the Advanced Study Institute on "Sensory Perception and Transduction in Aneural Organisms" and this book possible. Finally. we are also indebted to Ms. Pat Parham Morgan who expertly retyped all the chapters of the book and Ms. Leslie Schmidt of Plenum Publishing Co. provided us valuable advice and suggestions on the preparation of this book. G. Colombetti F. Lenci P. S."