Development and function of the larval nervous system in molluscs

The nervous systems of molluscs show a diversity which surpasses that of any other phylum, except perhaps the chordates. The brains and behaviours of cephalopods such as the octopus were even the subjects of fascination for Aristotle, while both the brain and behaviour of sedentary chitons can be described only as rudimentary at best. Moreover, special characteristics of the molluscan nervous system (i.e., their giant cells) have been exploited in Nobel Prize winning research. And yet, we know very little about how the molluscan nervous system develops or how such diversity is generated. Furthermore, knowledge of neural development derived from other organisms such as flies, worms and mammals appears inadequate to resolve this issue. This application proposes to examine the full complement of cells that comprise the nervous system as it first develops, focusing particularly on larval stages of gastropods which may best represent the ontogenetic origins of ancestral molluscs. A more complete view of the components of the larval nervous system will in turn guide subsequent studies on its function. Understanding function in turn provided insights into forces shaping the evolution of the nervous system of the phylum as a whole and of the different classes within. We will particularly focus on the roles of identified cells and cell types in behaviours that allow the larvae to orient to chemicals, light, currents and gravity. Finally, we will investigate the developmental mechanisms responsible for formation of the molluscan nervous system, paying particular attention to the initial steps in generation of neuronal cell types. The hypothesis that the diversity of brain structures observed within molluscs derives from a diversity of mechanisms underlying early neuronal development will be tested by examining the origins of different regions of the nervous system in animals ranging from cuttlefish to snails. While aimed largely at a better understanding of the diversity of life around us, the work also has implications for understanding the important larval stages of animals that constitute major components of our ocean ecosystems and are also prized foods from aquaculture.