Abstract:

 Objective  To research the morphological characteristics and differential gene expression of Chrysomya megacephala eggs in different developmental stages.  Methods  After C. megacephala laid eggs（0 h）， the eggs were collected every 2 h until eggs hatched into larvae. The morphological characteristics of C. megacephala eggs in different developmental stages were observed by stereo microscopy and scanning electron microscopy. The total RNA of the fly eggs was extracted. The expression levels of bicoid， slalom and chitin synthase genes was determined by Real-time flourescence quantitative PCR. Statistic analyses were performed with SPSS 19.0.  Results  Under the stereomicroscope， at 0-4 h after egg laying， the morphological change of C. megacephala eggs was not obvious. At the 6th hour after egg laying， somites were formed. After 8 hours the eggs shriveled. At the 9th hour after egg laying， the eggs hatched into larvae. The scanning electron microscope images showed that the morphological change of eggs was not obvious in the first 4 hours， the end of micropyle slightly outward， the surface around the micropyle was smooth. At the 6th hour after egg laying， the end of micropyle began to sag and irregular protrusions formed around the micropyle. At the 8th hour the end of micropyle was obviously dented. After 9 hours larvae hatched from eggs. Real-time fluorescence quantitative PCR indicated that the expression levels of bicoid， slalom and chitin synthase genes from C. megacephala eggs regularly changed with the developmental stages. There was a significant difference in threshold cycle values among the three genes（P＜0.05）. Conclusion  The morphological characteristics of C. megacephala eggs change with the development stage. The levels of gene expression in different development period of C. megacephala eggs are different.

Key words: Chrysomya megacephala, Egg, Morphological structure, Differential gene expression