Sexual Heteromorphism Of Skinx Lizards And The Effects Of Temperature And Oxygen Concentration On Their Reproduction And Later Representation

Sphenomorphus incognitus and Scincella modesta are both scincid lizards(skinks)that the former is widely distributed in the southwest part of mainland China,southern parts of Taiwan,and the latter in the eastern and central part of China.We collected S.incognitus from several localities in Guangdong Province,Hainan province in late April to early June,and S.modesta from in Nanjing,Jiangsu province in late April to early May.In our study,S.incognitus were used to study 1)sexual dimorphism and female reproduction;2)influence of incubation temperature on female reproduction and offspring phenotype.S.modesta were used to study 3)influence of oxygen concentration on female reproduction and offspring phenotype.281(??/??=104/177)S.incognitus were measured to get the morphology and body weight data.Adults are sexually dimorphic in snout-vent length(SVL).The largest male and female were 107.9 mm and 109.9 mm in SVL,respectively.S.incognitus is sexually dimorphic species,with females being the larger sex.In adult S.incognitus,males are larger in head size(both head length and head width)though smaller in abdomen length than adult females of the same SVL.All these S.incognitus reared in constant temperature of 24? room.The smallest and largest reproductive females of S.incognitus were 81.4 and 107.6 mm in SVL,respectively.About 3 to 10 eggs were laid in each clutches.Clutch size,egg size and clutch mass were all positively correlated with maternal SVL.Incubation temperature of S.incognitus affected hatching success and hatching length.A total of 134 eggs were hatched in 5 constant temperatures and 2 fluctuating temperatures systematically.The incubation length of each treatment group was significantly different,with the largest one being the 22? but the smallest one being the 28?.Incubation length was negatively correlated with constant temperature.The highest hatching success was in 28?,but the lowest one was in 25±5?.There was no significant difference in hatching success among these treatments by G-test.The larval morphological data were obtained from three temperature treatment groups of 25?,25±3? and 25±5?.There was no significant difference in SVL of neonates among three thermal treatments.Head size of neonates did not differ among three thermal treatments with same SVL.All neonates were reared to 90 days,with all the larval size and weight being positively correlated with the number of feeding days.But there was no significant difference in the growth rate among these thermal treatments.Scincella modesta was used to study the influence of the oxygen concentration on female reproduction and offspring phenotype.27 females laid eggs in total,and the average SVL was 47.39mm,about 4-11 eggs were laid in each clutches.202 eggs were obtained in total,and embryonic stages at oviposition varied from 31to36.Incubation length was about 16 days.All these eggs were randomly placed at two different incubation group in Binder CB,oxygen concentration gradients are respectively 7%and 21%.Heart rate and wet weight of embryos and residual yolk dry weight were recorded in 0 days,8th days and 16th days.It suggested that heart rate and wet weight were all positively correlated with incubation days.Residual yolk dry weight was negatively correlated with incubation days,thus showing that the development of embryo rose with time.There was no significant difference in heart rate at the two treatments within same incubation days.But wet weight and residual yolk dry weight showed significant difference,thus signifying that hypoxia has inhibition effect on the growth and development of lizards 'embryo.Hatching success in the normoxia(78/81=96.3%)was larger than hypoxia(17/79=21.5%),thus indicating that hypoxia inhibited the normal development of S.modesta and reduced offspring fitness meanwhile increased risk of death.Offspring phenotype and body mass of S.modesta were influenced by hypoxia.Body size was smaller in hypoxia than in normoxia.Head size of neonates showed significant difference at the two treatments with same SVL,with the abdomen length and body mass not showing significant difference.It showed that neonates of S.modesta were generally smaller by hypoxia incubation.Head sizes were smaller and the ability of food intake decreased,thus causing extremely low fitness for S.modesta.