Oocytes during Mid-Oogenesis

Drosophila melanogaster oogenesis displays a wide range of complex active dynamics over the course of many different stages. We have studied dynamics by injecting fluorescent nanospheres into oocytes during mid-oogenesis and imaging these probes using confocal optical microscopy, which yields sets of particle trajectories. In our analysis, we apply a novel statistical method to quantify the degree of correlated motion in proximate trajectories during stages 9 and 10b. Using these results, we identify local subsets of trajectories that exhibit non-random correlated motion at long times and then apply local collective motion (LCM) analysis. Consequently, we remove the correlated motion and obtain LCM-corrected mean square displacements (MSDs) that describe only the underlying random motion. This random motion is the result of passive Brownian entropic and active motor-driven excitations. Our analyses reveal strongly sub-diffusive behavior dominated by local elasticity in both stage 9 and 10b, but the associated power laws are different. By performing an objective local similarity analysis, we avoid characterizing ensemble averaged probe MSDs as simply convective, diffusive, or bound and reveal changes in local environments in the ooplasm that occur during these different stages.