蝘蜓头、体大小的两性异形和雌体繁殖

SEXUAL DIMORPHISM IN BODY SIZE AND HEAD SIZE AND FEMALE REPRODUCTION IN A VIVIPAROUS SKINK, Sphenomorphus indicus

报道了蜓 (Sphenomorphusindicus)头、体大小的两性异形和雌性繁殖。性成熟雌体大于雄体。雄性成体头长大于雌性成体 ,但头宽与雌性成体无显著差异。初生幼仔的头长和头宽无两性差异。雄性幼体头长和头宽大于雌性幼体。设置SVL恒定时 ,雄性幼体和雄性成体的头长和头宽无显著差异 ,雌性幼体的头长和头宽大于雌性成体。初生幼仔具有相对较大的头部。产仔雌体的最小SVL为 6 7 7mm ,大于此SVL的雌体均年产单窝仔。平均窝仔数、窝仔重和幼仔重分别为 7 2 ( 3～ 11)、 3 34( 1 30～ 5 19)和 0 48( 0 36～ 0 5 8)g。用卵黄沉积卵巢卵和输卵管计数的窝仔数比用幼仔计数的窝仔数多约 1 0个后代。幼仔体重与雌体SVL无关。相对窝仔重与雌体SVL边缘性地呈正相关。窝仔数、窝仔重与雌体SVL呈正相关 ,幼仔体重与窝仔数呈负相关。窝仔数与雌体状态无关。

We report data on sexual dimorphism in body size and head size and female reproduction for Sphenomorphus indicus from Hangzhou,Zhejiang,eastern China.The skink is sexually dimorphic in both body and head size,and females are larger in body size but smaller in head size.Except for neonates that did not exhibit sexual dimorphism in head size,males had larger heads than did females.When SVL was kept constant,we found that juvenile and adult males did not differ in head size but juvenile females had larger heads than did adult females.Heads of neonates were relatively the largest,implying the importance of larger heads for an individual's ability to use larger prey.The smallest reproductive female was 67 7?mm SVL,and all females larger than this size produced a single litter per season.Litter size,litter mass and neonate mass varied from 3 to 11 (mean=7 2) offspring,1 30 to 5 19 (mean=3 34) g and 0 36 to 0 58 (mean=0 48)?g,respectively.Litter size determined by counting the number of yolked follicles and oviductal eggs outnumbered that by counting the number of neonates by 1 0 offspring.Neonate mass was independent of maternal SVL,and litter size was independent of maternal conditions.Both litter size and litter mass were positively correlated with maternal SVL,and there was a marginally positive correlation between relative clutch mass and maternal SVL.An inverse relationship between neonate mass and litter size was found in S indicus ,suggesting a trade off between the two variables.Our data indicate that selection should favor larger body size in S indicus ,as females can increase their reproductive output through production of more offspring by increasing body size.Moreover,adult females partition relatively less resources into head growth but more into carcass growth,thereby leaving a larger space for producing more offspring.