The microstructure of the larval and early postlarval shells formed within the maternal body of the ovoviviparous prosobranch, C. japonica, was studied by scanning electron microscopy of polished and etched sections, fractured sections and developed mental surfaces. The larval shells are composed exclusively of the periostracum. The shell remains organic during the earliest postlarval stage, 1- to 1.5-whorl stage. A distinctive calcified shell layer composed of aragonite prisms of .apprx. 0.5-2 .mu.m in diameter is 1st formed in the later part of the body whorl at 2-whorl stage, and a 1st crossed-lamellar layer in the body whorl at 3-whorl stage. The apical parts of the shell formed during the larval and earliest postlarval stages are entirely calcified long after metamorphosis, .apprx. 3.5- to 5-whorl stage, to form the prismatic and normal crossed-lamellar or irregularly crossed-lamellar (protocrossed-lamellar) layers. Transition from the protocrossed-lamellar to the normal crossed-lamellar structure usually occurs in the middle part of the initial whorl.
CITATION STYLE
TOGO, Y. (1984). SCANNING ELECTRON MICROSCOPY OF LARVAL AND EARLY POSTLARVAL SHELLS IN THE FRESHWATER SNAIL, CIPANGOPALUDINA JAPONICA (V., MARTENS) (MESOGASTROPODA, VIVIPARIDAE). The Journal of the Geological Society of Japan, 90(8), 565-576_5. https://doi.org/10.5575/geosoc.90.565
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