Optical imaging techniques for investigating the function of earthworm nervous system

The earthworm is a suitable animal for investigating the relationships between its behavior and the function of its nervous system. However, this animal has not been widely used for neuroethological research because it is not a model organism. In this chapter, we describe the use of the earthworm as a plausible model for investigating locomotion activity and learning and memory abilities using several optical imaging techniques based on our previous studies. First, we demonstrate the usefulness of this animal briefl y, show its simple nervous system, and then focus on its locomotion mechanism in detail. Especially, we focus on experimental techniques using several fl uorescent dyes, e.g., FM1-43 for functional imaging of specific synapses and DAF for nitric oxide release from the ventral nervous system following different forms of stimulation. Finally, we conclude this chapter with a discussion on future studies of this animal with respect to learning and memory and imaging techniques.