This study aimed aimed at quantifying transcriptional profiles associated with circadian rhythms in intertidal copepods, and in testing for differences in cyclical transcription between populations from different latitudes. Such differences may help us understand the evolution of developmental rate variation among divergent populations within a species.</p><p>The experiment used copepods from Bird Rock, California, and Strawberry Hill, Oregon that had been acclimated to laboratory conditions for at least three generations. For each experiment, 25-day old adult male individuals, cultured in an incubator at 20C and 8:16 Light:Dark cycle, were sampled in pools of ~20 individuals at six different zeitgeber time points relative to light cycle. Two replicates per time point were sampled in each of two consecutive days (four replicates total). Total RNA was isolated using Trizol reagent, and sequencing library was prepared with the NEBNext Ultra II Directional RNA kit, using 300-500 ng of total RNA as input.