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Summary: 1021
ExtendedEggRetentionandltsInfluenceon
EmbryonicDevelopmentandEggWaterBalance:
lmplicationsfortheEvolutionofViviparity
TomMathies
RobinM.Andrews
Department of Biology, Virginia Polytechnic Ir-rstituteand StateUniversity,
Blacksburg, Virginia 24061-0406
Accelrted 11/1.7/95
Abstract
Vil)iparitJ, in squamate reptiles presumably euolues uia gradual increases in tbe
time tbat eggsare retained. witbin tbe ouiducts. lVe eualuated tbe extent and
consequences of pbenotypic plasticity in egg retention for tbe ouiparous lizard
Sceloporus scalaris. Tbis speciesnot only exbibitsfacultatiue egg retention, but
bas close relatiues tbat are uiuiparous. Tbus, S. scalaris ma! possessreproductiue
Jbatures tbat are transitional between ouiparibt and uiuiParitJ,. ,ffe tested tbe b1,-
potbesis tbat ouiposition normally occurs wben furtber retention uould impair
embry677i6 d.euelopmen.t. To do so, we determined tbe efiects of extend.ed egg re-
teiltion on embryonic deuelopment and on egg water balance for a population
in wbicbJ'emales nctrmally retain eggsto Dufaure and Hubert stages31.O-33.5.
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