Genetics and Development of Circadian Rhythms in Invertebrates

The scope of this review includes the developmental ontogeny and genetics of the driving oscillator and overt rhythms in invertebrates. The discussion is generally confined to meta-zoan organisms, except in cases where comparison with data from lower organisms is useful. The terms pacemaker and oscillator are usually used in the singular, although the actual physiological pacemaker may be made up of components—a population of coupled oscillators—or, at least, represented bilaterally in the two hemispheres of the brain. Only true circadian rhythms—those that persist in constant conditions—are covered; diel rhythms, which are expressed in LD but not in constant conditions, are not discussed.