by far the strongest cases for a direct role of ionic currents in morphogenesis is the polarizing fucoid egg where the current is carried in part by ca2+ and generates an intracellular concentration gradient of this ion that orients the outgrowth , and the insect follicle in which an intracellular voltage gradient is responsible for the polarized transport from nurse cell to oocyte .
C0018120
follicle
C0029045
oocyte