F-actin is responsible for the biased motion of oil droplets toward the oocyte center. (A) Scheme explaining how the cumulative bias toward the oocyte center or cortex is measured. The black dots correspond to the centroid of objects. One track of an oil droplet centroid is presented with the directionality of motion depicted by an arrow for each time step. The nucleus is in blue. (B) Cumulative bias toward center and toward cortex for oil droplets. Black dots represent the oil droplet cumulative bias toward the center calculated for 17 different time steps from 29 different trajectories. Black diamonds represent the cumulative bias toward the cortex calculated for 17 different time steps from 29 different trajectories. The gray area represents the numerically constructed 99% confidence interval (CI) of cumulative bias values for n = 29 objects with a random motion (see Materials and methods). The cumulative biases outside this interval are likely generated by a biased motion (P value of 0.01). (C) Cumulative bias toward center and toward cortex for oil droplets in oocytes treated with Cyto D. Black dots represent the oil droplet cumulative bias toward the center calculated for 17 different time steps from 29 different trajectories. Black diamonds represent the cumulative bias toward the cortex calculated for 17 different time steps from 29 different trajectories. The gray area represents the numerically constructed 99% confidence interval of cumulative bias values for n = 29 objects with a random motion (see Materials and methods). The cumulative biases outside this interval are likely generated by a biased motion (P value of 0.01).