It is now widely accepted that Hexapoda emerged from Crustacea. Compared to the ubiquitous calcified exoskeleton in crustaceans, a mineralized cuticle in insects is extremely rare. Catecholamine-driven protein cross-links play a leading role in the sclerotization of insect cuticle. In this study, mineralization was discovered in the pupal cuticle of Bactrocera dorsalis (Diptera: Tephritidae), a common pest of fruit farms. We mainly profiled the features of mineralized pupal cuticles from B. dorsalis and its white mutant B. dorsaliswh and unmineralized cuticle from Musca domestica using high-resolution field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with structural analysis involving infrared (IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and synchrotron X-ray absorption near-edge structure (XANES) spectroscopy. We also compared the thermodynamic and mechanical properties of different pupal cuticles. The results showed that the pupal cuticles of B. dorsalis contain a phase of stable amorphous calcium phosphate (ACP) with a high level of magnesium, which is mainly distributed in the exocuticle and assists in the formation of a graded, stiffened cuticle structure. Unexpectedly, this ACP possesses a very low Ca/P ratio and has a composition similar to that of CaHPO4·2H2O. The degree of mineralization in the pupal cuticle of B. dorsaliswh (approximately 22 wt%) is significantly greater than that of wild-type B. dorsalis (approximately 12 wt%), which indicates that there may be a connection between the biomineralization and tyrosine-mediated tanning pathways. These findings provide new evidence for the mineralization of the insect cuticle, which may shed new light on the evolutionary mechanism underlying the divergence of cuticle sclerotization between insects and crustaceans.

中文翻译：

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Bactrocera dorsalis Hendel（Diptera：Tephritidae）的cut表皮中的无定形磷酸钙：重新考虑昆虫表皮矿化的新发现。

现在，人们普遍认为六足纲是从甲壳纲出现的。与甲壳动物中普遍存在的钙化外骨骼相比，昆虫中的矿化角质层极为罕见。儿茶酚胺驱动的蛋白质交联在昆虫表皮的硬化过程中起主要作用。在这项研究中，在果园常见的害虫Bactrocera dorsalis（Diptera：Tephritidae）的cut表皮中发现了矿化作用。我们使用高分辨率场发射扫描电子显微镜（SEM）和透射电子显微镜（TEM）结合结构分析，主要分析了背侧双歧杆菌及其白色突变体背侧双歧杆菌的矿化p角质层和家蝇的未矿化角质层的特征。红外（IR）光谱，X射线衍射（XRD），X射线光电子能谱（XPS），和同步加速器X射线吸收近边缘结构（XANES）光谱。我们还比较了不同p角质层的热力学和机械性能。结果表明，背侧双歧杆菌的cut角质层含有稳定的无定形磷酸钙（ACP）相，其中镁含量很高，镁主要分布在角质层内，有助于形成逐渐变硬的角质层结构。出乎意料的是，该ACP具有非常低的Ca / P比，并且具有类似于CaHPO4·2H2O的组成。B. dorsaliswh（约22 wt％）的cut角质层中的矿化度显着大于野生型B. dorsalis（约12 wt％）的矿化度，这表明生物矿化与酪氨酸之间可能存在联系介导的晒黑途径。