Figure 5.

Schematic representation of C. merolae’s phototactic mechanism. (A) Light or salt stress trigger actin polymerisation from an existing pool of G-actin. (B) The growing filaments push against the plasma membrane forming the observed bulb. (C) As membrane-shaping I-BAR proteins are missing, a random F-actin bundle prevails to form the growing tentacle. In the tentacle’s shaft, parallel actin filaments drive the elongation, whereas contraction of circular filaments in the tentacle head allows attachment to a surface. (D) Actin depolymerisation and membrane tension enable the retraction of the tentacle.