Eggshell Structure of the Siamese Narrow-headed Softshell Turtle Chitra chitra Nutphand, 1986 (Testudines: Trionychidae)

Abstract

Eggs of Chitra chitra were examined for: 1) eggshell thickness by stereo-microscope, 2) eggshell structure by scanning electron microscopy (SEM), 3) qualitative and quantitative elements of eggshell structure by energy dispersive x-ray analysis (EDX), and 4) eggshell composition by X-ray diffraction analysis. It was found that the eggshell thickness of the outer layer and inner layer detected by stereo-microscope were 0.14±0.02 mm and 0.12±0.02 mm, respectively. The result of SEM showed that the eggshell had three layers; an outer calcareous sheet (previously unseen), a middle crystalline layer, and an inner fibrous layer. The eggshells were composed of oxygen=53.0±4.8%, carbon=35.0±9.2%, magnesium=5.55±0.34%, calcium=5.4±7.2%, silica=2.9±1.6%, aluminum=2.3±1.1%, potassium=0.17±0.1%, and sodium=0.74±0.3%. The eggshell was the aragonite form of CaCO3