【摘 要】
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The majority of extant reptiles are oviparous and produce eggs with three major components:embryo,yolk,and eggshelll.The eggshell is species-specific and more diverse in squamate reptiles than in other amniote taxa.Here,we study the crystal structure,chem
【机 构】
：
College of Life and Environmental Sciences,Wenzhou University,Wenzhou 325035,Zhejiang,China;Faculty
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The majority of extant reptiles are oviparous and produce eggs with three major components:embryo,yolk,and eggshelll.The eggshell is species-specific and more diverse in squamate reptiles than in other amniote taxa.Here,we study the crystal structure,chemical composition,and bonding states of the eggshell of the green crested lizard Bronchocela cristatella.X-ray diffractometer(XRD) analysis showed the existence of two clearly defined and distinguishable crystalline phases,aragonite and calcite.Using the XRD data and a unit cell refinement routine,we identified two sets of cell parameters:a =4.956 (A),b =7.965 (A),and c=5.734 (A) for the aragonite phase;a =4.987 (A),b =4.987 (A),and c=17.056 (A) for the calcite structure.We used x-ray photoelectron spectroscopy to examine detailed elemental composition and bonding states and found that the eggshell was composed primarily of elements C,N,Ca,and O,with C,N and O bonded to various types of hybridization in the protein of the eggshell membrane.The Ca∶C∶O ratio for the calcium carbonate yielded a value of ～7∶8∶21,which is close to the expected stoichiometric value of CaCO3.
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