Embryonic development of the Glossiphoniid leech Theromyzon rude: Characterization of developmental stages☆

摘要

TheembryonicdevelopmentoftheleechTheromyzonrudewasstudiedunderthedissectingmicroscope.Embryoswereexaminedbothliveandafteracidtreatmentthatsolubilizestheyolk,orvitelloplasm,andrenderstheembryostransparent.Mostoftheremainingcytoplasm,orteloplasm,oftheuncleavedeggispassedontofivepairsofgerminalcells,orteloblasts.Teloblastsarisesequentiallyfromasetofprecursorcells,orproteloblasts,thatdivideaccordingtoamodifiedspiralcleavagepattern.Eachteloblastbudsoffasuccessionofsmallerstemcells,whichformasinglerow,orgerminalbandlet,andtowhichtheteloblastpassesonitsteloplasm.Thefivebilateralpairsofgerminalbandletsthusproducedgiverisetomostoftheembryonicstructures.Anewnotationalsystemforthedesignationofproteloblasts,teloblasts,andtheirstemcellshasbeenintroduced.Developmentoftheembryo,fromtheuncleavedeggtothecompletionofthegut,hasbeendividedinto10stages.At14?°C,completionofthese10stagestakesapproximately850hrfromthetimetheeggislaid.