Understanding the evolution of the developmental programs active during dipteran embryogenesis depends on comparative studies. As a counterpoint to the intensively investigated and highly derived cyclorrhaphan flies that include the model organism Drosophila melanogaster, we are studying the basal Diptera Bradysia hygida, a member of the Sciaridae family that is amenable to laboratory cultivation. Here we describe the B. hygida embryogenesis, which lasts 9 days at 22 °C. The use of standard fixation D. melanogaster protocols resulted in embryos refractory to DAPI staining and to overcome this, a new enzyme-based method was developed. Calcofluor-White staining of enzimatically-treated embryos revealed that this method removes chitin from the serosal cuticle surrounding the B. hygida embryo. Chitin is one of the main components of serosal cuticles and searches in a B. hygida embryonic transcriptome database revealed conservation of the chitin synthesis pathway, further supporting the occurrence of chitin biosynthesis in B. hygida embryos. Combining the enzymatic treatment protocol with the use of both DIC and fluorescence microscopy allowed the first complete description of the B. hygida embryogenesis. Our results constitute an important step towards the understanding of early development of a basal Diptera and pave the way for future evo-devo studies.

中文翻译：

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表征 B. hygida（双翅目：Sciridae）在酶处理后使浆膜角质层渗透的胚胎发育

了解双翅目胚胎发生过程中活跃的发育程序的演变取决于比较研究。作为对包括模式生物黑腹果蝇的深入研究和高度衍生的 cyclorrhaphan 苍蝇的对比，我们正在研究基础双翅目蚱蜢，它是适合实验室培养的 Sciridae 家族成员。在这里，我们描述了 B. hygida 胚胎发生，它在 22°C 下持续 9 天。使用标准固定 D. melanogaster 协议导致胚胎对 DAPI 染色难治，为了克服这个问题，开发了一种新的基于酶的方法。酶处理过的胚胎的 Calcofluor-White 染色表明，这种方法可以从 B. hygida 胚胎周围的浆膜角质层中去除几丁质。几丁质是浆膜角质层的主要成分之一，在 B. hygida 胚胎转录组数据库中的搜索揭示了几丁质合成途径的保守性，进一步支持了 B. hygida 胚胎中几丁质生物合成的发生。将酶处理方案与 DIC 和荧光显微镜的使用相结合，首次完整地描述了 B. hygida 胚胎发生。我们的结果是了解基础双翅目早期发育的重要一步，并为未来的进化研究铺平了道路。将酶处理方案与 DIC 和荧光显微镜的使用相结合，首次完整地描述了 B. hygida 胚胎发生。我们的结果是了解基础双翅目早期发育的重要一步，并为未来的进化研究铺平了道路。将酶处理方案与 DIC 和荧光显微镜的使用相结合，首次完整地描述了 B. hygida 胚胎发生。我们的结果是了解基础双翅目早期发育的重要一步，并为未来的进化研究铺平了道路。