Mature oocyte (MO) of B. areolata.
a MO of the normal female. b Ooplasm of the MO of the imposex female. c The cortical ooplasm of the MO of the normal female. Note the exocytotic vesicles (arrows) and the outfolding of the ooplasmic membrane (arrowhead) before forming microvilli. d The periphery of the MO of the normal female showing microvilli (asterisk) and exocytotic vesicles (arrows). CG cortical granule, G Golgi body, M mitochondria, N nucleus, Nu nucleolus, V electron-lucent vesicle, Y yolk body. Scale bars = 0.4 μm (c), 0.8 μm (d), 1 μm (b) and 2 μm (a)