In constant dark, <i>DmIh</i> mutant flies shorten the circadian period.

<p>Average (top) and single fly representative (middle and bottom) double-plotted actograms of control and <i>DmIh</i> mutant flies in DD conditions. Flies were entrained for three days in LD conditions prior to being released to DD. The first day of each actogram corresponds to the last day in LD. Mutant flies included rhythmic flies (Ih-R), weakly rhythmic flies (Ih-WR), and arrhythmic flies (Ih-A) (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036477#pone-0036477-t001" target="_blank">Table 1</a> for circadian parameters). Rhythmic mutant flies display a shorter period and a failure to maintain the activity plateau during the subjective day.