What keeps Caenorhabditis elegans precise: The spatiotemporal regulation of defecation

Rhythmic behaviors controlled by internal biological clocks are universal among living organisms, ranging from single cells to humans. The inner workings and modulations of the intrinsic oscillatory activities that underlie these rhythmic behaviors are diverse and not well understood across different systems. The Caenorhabditis elegans defecation behavior, also known as the defecation motor program, is a particularly intriguing rhythmic behavior that has been studied for over 30 years since James Thomas' pioneering work in 1990. Numerous conserved genes and signaling molecules have been identified through meticulous studies of every detail of its genetics, physiology, and behavior. Since earlier works have been reviewed until 2006 in the literature, this review is not intended to be comprehensive and will instead focus on progress since then, with emphases on intestinal calcium and proton oscillations as well as the modulation of the defecation rhythm by the enteric nervous system.