Backscattered electron (BSE) images of gekkotan eggshells.

Abstract

<p>White bars on the side represent the certain boundary mentioned in the text and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199496#pone.0199496.s001" target="_blank">S1 Text</a>. Outside of eggshell is up. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199496#pone.0199496.s011" target="_blank">S9</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199496#pone.0199496.s017" target="_blank">S15</a> Figs for details. (A) <i>Gekko gecko</i>. White arrows point to the circular structures with a central hole, whereas black arrows mark the vesicles. Note the enigmatic bulbous structure in ornamentation (a white arrowhead) covered with a very thin layer consisting of polygonal structure in the outermost part of the eggshell (a black arrowhead). (B) <i>Paroedura pictus</i>. Note the circular structures with a central hole (white arrows) and abundant vesicles (black arrows). The ridge-like ornamentation is marked by a black arrowhead. (C) <i>Paroedura stumpfii</i>. Circular structures with a central hole (white arrows) are distributed in the eggshell except the inner portion of the plain layer. Vesicles are marked by black arrows. Note the highly irregular pores in the porous layer and a pore-like orifice (a black arrowhead). (D) <i>Phelsuma grandis</i>. Abundant circular structures (white arrows) and a few vesicles are present (black arrows). Note needle-like structures between the blocky and columnar layers (two lower white arrowheads). Spherical granular ornamentations are connected to the main eggshell (two upper white arrowheads) covered with a very thin covering layer (a black arrowhead). (E) <i>Correlophus ciliatus</i>. The boundary layer is marked by a dashed line. Note that calcareous layer occupies one-half of the eggshell although they coexist with protein fibers (fibers are represented by black dots and lines; white arrows). Pore-like and small chamber-like structures are pointed by black and white arrowheads, respectively. (F) <i>Rhacodactylus leachianus</i>. The boundary layer of the eggshell is marked by a dashed line. It has deeper mixed layer with a more compact outer portion than <i>Correlophus ciliatus</i> eggshell. The protein fibers are marked by white arrows. Note pore-like structure (a black arrowhead). (G) <i>Eublepharis macularius</i>. Columnar structure is clearly observable with pore-like structures between columns (black arrowheads). The stem-like structure of each columns consists of calcite and protein fibers (white arrows).</p