Exploration of the Developmental Changes of the Midgut of Silkworm Larvae during Pupal Metamorphosis
In order to explore the developmental changes of silkworm larvae in the process of pupal met-amorphosis,the midgut of the fifth instar larvae,pupal and moth stages of silkworm was anatomically ob-served at 24 h intervals.The results showed that the midgut of the fifth instar larvae of silkworms was long cylindrical,green and enlarged in the mulberry feeding stage,and the midgut began to turn yellow and shorten after the silkworm larvae stopped eating mulberry at the mature silkworm stage.In the process of molting and metamorphosing into a pupa of mature silkworms,the midgut continues to shorten and become smaller,and with the prolongation of the development period,it finally becomes oval granu-lar,and the surface color changes from light yellow to brownish yellow.Further observation of paraffin sections of midgut tissues at different developmental stages of silkworms showed that larval midgut cells underwent multiple processes of apoptosis and regeneration during pupal metamorphosis.New midgut epi-thelial cells are formed at 3-4 days,7-8 days,and 12 days-moth periods in cocooning,and these new mid-gut epithelial cells may be differentiated and renewed from regenerative cells.The expression patterns of apoptosis genes (Caspase-1,BmDredd)and autophagy genes (Atg1,Atg13)showed that the expression levels of Caspase-1 and BmDredd were decreased at 2 days,7 days and 12 days in cocooning,and the ex-pression levels of Atg1 and Atg13 were decreased at 7 days,9 days,and 12 days in cocooning,suggesting that apoptosis of intestinal cells was inhibited during these periods,which were largely consistent with the formation of new midgut epithelial cells in the section results.The results of this study showed the devel-opmental changes of the larval midgut during the pupal metamorphosis period,indicating that the midgut of the silkworm larval did not completely die out during the pupal metamorphosis,and the adult midgut was developed by the larval midgut after multiple deaths and regeneration during the pupal metamorphosis period.
万方数据
维普
