Scanning electron microscopy of Drosophila embryogenesis: 1. The structure of the egg envelopes and the formation of the cellular blastoderm☆

[摘要] AspartofaseriesofdetailedobservationsonembryogenesisinDrosophila,theprotectivecoveringsoftheeggandsurfacechangesintheembryopriortogastrulationhavebeenstudiedwiththeSEM.Fourspecializationsofthechorionaredescribed:theplastron,micropylarcone,operculum,andtheposteriorthickening.Afterremovaloftheprotectivecoveringsthesurfacechangesduringdevelopmentcanbeobserved.Duringthefirsteightsynchronousnucleardivisionsadensearrayofthinmicroprojectionscoversthewholeembryo.Aftertheninthdivisionbetween373and408nucleireachthesurfaceandbecomelocatedincytoplasmicprojections.Fromcountsofthenumberofsurfacebulgesduringthesyncytialblastemastages,itwasestablishedthat13synchronousdivisionstakeplaceproducingbetween5600and6500surfacenuclei.Duringformationofthecellularblastoderm,thelocationoftheprospectivecellsbecomesobscuredbyadensepatternofmicroprojectionsfromeachcell.However,withthecompletionoftheblastoderm,thesurfacesofthecellsbecomesmoothandthecelloutlinesdistinct.TheusefulnessoftheSEMindevelopmentalstudiesisdiscussed.

[学科分类] 生物科学（综合）