  Life in complex systems, such as cities and organisms, comes to a standstill
when global coordination of mass, energy, and information flows is disrupted.
Global coordination is no less important in single cells, especially in large
oocytes and newly formed embryos, which commonly use fast fluid flows for
dynamic reorganization of their cytoplasm. Here, we combine theory, computing,
and imaging to investigate such flows in the Drosophila oocyte, where streaming
has been proposed to spontaneously arise from hydrodynamic interactions among
cortically anchored microtubules loaded with cargo-carrying molecular motors.
We use a fast, accurate, and scalable numerical approach to investigate
fluid-structure interactions of 1000s of flexible fibers and demonstrate the
robust emergence and evolution of cell-spanning vortices, or twisters.
Dominated by a rigid body rotation and secondary toroidal components, these
flows are likely involved in rapid mixing and transport of ooplasmic
components.
