Embryogenesis of peripheral nerve pathways in grasshopper legs: II. The major nerve routes☆

摘要

Intheprecedingpaper(H.KeshishianandD.Bentley,1983a,Dev.Biol.96,89a€“102)theeventsleadingtothemorphogenesisofnerve5B1inthegrasshopperembryonicmetathoraciclegwerepresented.Heretheroleoflaterdifferentiatingperipheralneuronsinestablishingtheothermajornervesofthelegisexamined.Inadditiontothe(tibial1)(Ti1)pioneerneuroncellpairsthatestablishnerve5B1inthetibia,femur,andcoxa-trochanter,sixlaterdifferentiatingcellsand/orcellpairswereidentifiedandexaminedwithrespecttotheirroleinperipheralnerveontogeny.Nervepathpioneeringwasobservedintwocellpairsofthedistaltarsus(Ta1andTa2),byneuronsoftheposteriorproximaltibia(Ti2),theposteriormidfemur(neuronsF3andF4),andbyanadditionalcellpairintheanteriorcoxal-trochanteralregionofthelimbbud(cellpair,CT2).Inaddition,efferentprojectionsontolimbbudepitheliaplayedanimportantroleinestablishingnervebranches.IntwonervestheaxonaltrajectoryfromtheperipherytotheCNSisestablishedbyafferentandefferentpathfindingaxonsmeetinghalfwayandovergrowingeachother'sestablishedprojections.Foreachnervebranchexamineditwasfoundthataxonsprojectedinitiallytothecellbodiesofpreviouslyarisingneuronsalongthetrajectory.Thelocationalongthelimbbudectodermwhereneuronsarise,andhencetheirultimatecellbodypositions,playedanimportantroleinorganizingthefasciculationoffolloweraxonsandestablishingbranchpoints.