Postfertilization growth of microvilli in the sea urchin egg: New views from eggs that have been quick-frozen, freeze-fractured, and deeply etched☆

摘要

Wehaveusedquick-freezing,freeze-fracture,anddeepetchingtostudypostfertilizationgrowthofmicrovilliintheseaurchin,Strongylocentrotuspurpuratus.Between1and2minpostinsemination,weobservedrapidgrowthofnumerousfinger-likemicrovillitoabout0.7??minlength.Subsequently,groupsoftwotofourmicrovillibecameraisedofftheeggsurfaceonbroadcytoplasmicbases.Finally,by5minpostinsemination,thesebaseshadbecomeinterconnectedbythinsheetsofcytoplasmtoformacontinuousnetworkofrufflesacrosstheeggsurface.Correspondingthinsectionsofquick-frozenandfreeze-substitutedeggsshowedthatthesemicrovillicontainednetworksofmicrofilaments.Thefinger-likeprocesseshadbundlesofparallelmicrofilamentsthatrantheirentirelength,whiletherufflesofcytoplasmcontainedsheetsofcrisscrossedmicrofilaments.Theseobservationssupportthehypothesisthatmicrovillargrowthresultsfromformationofnewmicrofilamentnetworks.