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. 2012 Mar 20;(176):55–72. doi: 10.3897/zookeys.176.2418

Figure 2.

Figure 2.

Structure of distal chorion (ch) and proximal vitelline membrane (vm), covering Porcellio scaber mid-stage embryo. A The mid-stage embryo with visible limb buds (lb) and midgut glands primordia (mg). B Semithin section of the embryo peripheral region. Chorion is separated from the embryo surface. The vitelline membrane is slightly detached from the embryo cells; * - a wider space between embryo surface and vitelline membrane. C, D TEM micrographs of one-layered chorion, including electron lucent “lacunae” (white arrow). E, F TEM micrographs of vitelline membrane, composed of three layers: main proximal homogenous layer (*), thin middle electron dense layer (white arrow) and superficial corrugated lucent layer (black arrow). Bars: A 200 µm; B 10 µm; C, E 0.5 µm; D, F 200 nm.