Comparative characterization of the oestrous cycles of the grasscutter (Thryonomys swinderianus) and the guinea pig (Cavia porcellus) by the hystricomorph vaginal membrane perforation phenomenon

摘要

Thegrasscutter(Thryonomysswinderianus)isahystricomorphrodentundergoingdomestication;thereforetofacilitateandenhanceitsbreedingincaptivityitsoestrouscyclewascharacterized.Forbetterelucidation,itsoestrouscyclewasstudiedalongsidethatoftheguineapig(Caviaporcellus),adomesticatedspontaneousovulatinghystricomorphrodent.Sexuallymaturegrasscuttersandguineapigsweremonitoredforthemanifestationoftheperiodicvaginalmembraneperforationphenomenon,whichisasignofoestrouscyclinginhystricomorphrodents.Theoestrouscyclewascharacterizedwithrespecttoitstimeofoccurrence,constituentphasesandduration.Thegrasscuttersmanifestederraticoestrouscycleswithsignificantlydifferentlengths,whiletheguineapigsmanifesteduniformoestrouscycleswithnosignificantdifferences.Theoestrouscyclesinbothspeciesconsistedoftwophases:oneofsexualactivityandtheotherofsexualinactivity.Inthegrasscutter,thesexualactivityphasewasrepresentedbyanopenorsecretion-sealedvagina,whileintheguineapigitwassolelyrepresentedbyanopenvagina.Thephaseofsexualinactivityinbothspecieswasrepresentedbyaninaccessiblevaginaclosedofftheexteriorbyanepithelialmembrane.Themeanlengthoftheoestrouscyclewas17.5#177;21.3daysand15.9#177;2.1daysinthegrasscutterandguineapigrespectively.Thegrasscutterpresentedameanopen/sealedperiodof11.1#177;25.9daysandameanclosedperiodof12.5#177;22.4days.Theguineapigspresentedameanopenperiodof3.1#177;1.1daysandameanclosedperiodof12.9#177;1.71days.Sincethegrasscuttersmanifestedanerraticoestrouscyclewhilethespontaneousovulatingguineapigsmanifestedauniformcycleitcouldbeinferredthatthegrasscutterisaninducedovulatorlikethecuis(Galeamusteloides),aninducedovulatinghystricomorphthatalsomanifeststhephenomenoninasporadicmanner.