Sperm incorporation, the pronuclear migrations, and their relation to the establishment of the first embryonic axis: Time-lapse video microscopy of the movements during fertilization of the sea urchin Lytechinus variegatus

[摘要] Themovementsduringfertilizationhavebeeninvestigatedwithdifferentialinterferenceopticsandrecordedbytime-lapsevideomicroscopyofthecleareggoftheseaurchinLytechinusvariegatus.Sperm-eggbindingoccursrapidly,andfollowingatimewhenthespermgyratesontheeggsurface,gametefusionoccurs.Arapidcorticalcontractionradiatesfromthefusionsiteandissucceededbytheelevationofthefertilizationcoat.Spermincorporationoccursintwostages:thefertilizationconeenlargesaroundandabovetheerectandimmotilespermandthenthespermhead,midpiece,andtailaredisplacedalongthesubsurfaceregionoftheeggatanaveragerateof3.5μm/min.Theformationofthespermastermovesthemalepronucleusfromthesubsurfaceregionoftheeggtowardtheeggcenteratarateof4.9μm/min.Whentheraysoftheradialspermasterappeartocontactthefemalepronucleus,thefemalepronucleusmigratesatarateof14.6μm/mintothecenterofthespermaster.Thenowadjacentpronucleiaremovedtotheeggcenterbythecontinuingenlargementofthespermasteratarateof2.6μm/min.Syngamyisusuallyprecededbythedisassemblyofthespermaster.Thecentripetalmigrationofthepronucleiappearsinvolvedintheestablishmentofthefirstembryonicaxis;cleavageoccurswithin8°ofthedirectionofthiscenteringmotion.

[学科分类] 生物科学（综合）