棘胸蛙的两性异形及生殖力

Sexual Dimorphism and Fecundity of Quasipaa spinosa

随机选取湖南石门性成熟棘胸蛙(Quasipaa spinosa)103只(雌性53只,雄性50只),通过测量和比较头体长等16个形态数量性状以及体重等10个重量数量性状,用独立样本t-检验和协方差分析的方法检验该物种所有数量性状的两性差异,并用线性回归法分析其生殖力与体大小之间的关系。结果表明:棘胸蛙平均体长,雄性为(101.27±1.80)mm,雌性为(101.02±1.18)mm,两性异形指数为0.002,雌雄个体的头体长和体重间差异不显著(P>0.05)。其他局部性形态数量性状与头体长都呈正相关(P<0.05)。雄性个体的头长、头宽、前臂及手长、手长、前臂宽、腿长、胫长和胫宽显著高于雌性。从局部形态特征看,湖南石门棘胸蛙属于雄性体型较大类型。雄性个体的皮重、心脏重、肺脏重和肾脏重显著高于雌性,雌性个体的性腺重、肝脏重和脂肪重明显高于雄性。肝脏重在雌雄群体中均与16个形态性状显著相关(P<0.05)。雄性会强化有利于捕食和繁殖的形态特征,故在性选择中雄性更占优势。棘胸蛙雌雄间存在显著差异的重量数量性状与繁殖、呼吸及消化代谢等功能密切相关。雌性生殖力与体大小呈正相关的结果支持生殖力选择压力假说。雄性个体可通过增加体大小来提高生殖力,从而提高自身被雌性选择的竞争力。在性选择、生殖力选择等压力作用下,棘胸蛙形态特征与功能性器官组织随性别分化且相关性显著,促进其两性异形的进化。

103 adults(53 females and 50 males)of the Quasipaa spinosa were randomly collected from Shimen Country,Hunan Province.16 morphological quantitative characteristics(such as snout-vent length)and 10 gravimetric quantitative characteristics(such as body mass)of them were measured.The sexual difference of quantitative characteristics were tested by the independent sample t-test and covariance analysis.The relationship between fecundity and body size was analyzed by linear regression.The results showed that the average body length of male and female Q.spinosa was 101.27±1.80 and 101.02±1.18 mm,respectively,and the hermaphrodite index was 0.002.There was no significant difference in snout-vent length and body mass between males and females(P>0.05).Other local morphological quantitative traits were positively correlated with snout-vent length(P<0.05).The head length,head width,length of lower arm and hand,hand length,width of lower arm,hindlimb length,tibia length,tibia width of male individuals were significantly higher than that of females.From the perspective of local morphological characteristics,the Q.spinosa of Hunan Shimen belongs to male-larger type.Males have significantly higher skin mass,heart mass,lung mass,and kidney mass than females.Females have significantly higher gonad mass,liver weight and fat weight than males.Liver mass was significantly associated with 16 morphological traits in both male and female populations(P<0.05).Males are more dominant in sexual selection by strengthening the morphological characteristics that are conducive to predation and reproduction.The gravimetric quantitative characteristics of Q.spinosa that are significantly different between males and females are closely related to the functions of reproduction,respiration,digestion and metabolism.The positive correlation between female fecundity and body size supports the hypothesis of fecundity selection pressure.Males'competitiveness in being selected by females was improved by increasing their fecundity with the body size.Under the pressures such as sexual selection and fecundity selection,morphological characteristics and functional organs or tissues of Q.spinosa differentiate with sex and are correlated significantly with each other,promoting the evolution of their sexual dimorphism.