5.8 Cytoplasmic Flow
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Fig. 5.27 (a) Sketch of circulation induced by the actomyosin cortex (Illukkumbura et al, 2020).
(b) Streamlines (light blue lines) of the 3D cytoplasmic flow field. The horizontal plane shows its
2D cross-section. (c) Cross-section through the 3D field shown in panel (b), with arrows indicating
flow directions and colors coding flow speeds. (d) Confocal image of a live stage 9 oocyte. Arrows
show the flow field computed from particle image velocimetry in the Drosophila oocyte (Trong et
al, 2015)
This flow mechanism prevails when the egg chamber is stiff, as it is, besides
Drosophila, in other animals with a bilateral body plan. However, it is different in
the soft oocytes of starfish, an animal with polar symmetry. Klughammer et al (2018)
modeled flow driven by a band of increased surface tension moving over the oocyte
cortex and compared the results with experimental flow and deformation patterns.
A good fit could be taken as a proof that the latter are fully determined by surface
contraction waves.
This kind of intracellular flow is characteristic of blebbing motion (Fig. 5.28),
where cytoplasm passively fills amoeboid protrusions, which are formed due to
cortex contractions. It is an efficient means of transportation, akin to peristaltic
streaming. Physarum polycephalum plasmodial slime mold (Fig. 5.29a), a very
special unicellular organism joining many nuclei into a huge cell spreading out up
to a meter long, builds up a true vascular network (Fig. 5.29b), where cytoplasm
is driven peristaltically. This network develops at the leading edge of the spreading
organism and thereby shapes its morphology. It is reputed to be a clever planner: if
put in a maze, the network reshapes to connect two exits by the shortest path. If pieces
of food are put at certain locations, slime mold connects them by the optimal road
network taking into account density of traffic between nodes. This planning ability
Fig. 5.28 Cytoplasmic flow during the creation of a bleb. Scale bar 5 μm (Goudarzi et al, 2019)
111
Fig. 5.27 (a) Sketch of circulation induced by the actomyosin cortex (Illukkumbura et al, 2020).
(b) Streamlines (light blue lines) of the 3D cytoplasmic flow field. The horizontal plane shows its
2D cross-section. (c) Cross-section through the 3D field shown in panel (b), with arrows indicating
flow directions and colors coding flow speeds. (d) Confocal image of a live stage 9 oocyte. Arrows
show the flow field computed from particle image velocimetry in the Drosophila oocyte (Trong et
al, 2015)
This flow mechanism prevails when the egg chamber is stiff, as it is, besides
Drosophila, in other animals with a bilateral body plan. However, it is different in
the soft oocytes of starfish, an animal with polar symmetry. Klughammer et al (2018)
modeled flow driven by a band of increased surface tension moving over the oocyte
cortex and compared the results with experimental flow and deformation patterns.
A good fit could be taken as a proof that the latter are fully determined by surface
contraction waves.
This kind of intracellular flow is characteristic of blebbing motion (Fig. 5.28),
where cytoplasm passively fills amoeboid protrusions, which are formed due to
cortex contractions. It is an efficient means of transportation, akin to peristaltic
streaming. Physarum polycephalum plasmodial slime mold (Fig. 5.29a), a very
special unicellular organism joining many nuclei into a huge cell spreading out up
to a meter long, builds up a true vascular network (Fig. 5.29b), where cytoplasm
is driven peristaltically. This network develops at the leading edge of the spreading
organism and thereby shapes its morphology. It is reputed to be a clever planner: if
put in a maze, the network reshapes to connect two exits by the shortest path. If pieces
of food are put at certain locations, slime mold connects them by the optimal road
network taking into account density of traffic between nodes. This planning ability
Fig. 5.28 Cytoplasmic flow during the creation of a bleb. Scale bar 5 μm (Goudarzi et al, 2019)