| Popis: |
Body temperature is the most important physiological variable affecting the performance of ectothermic animals.In June and October of 2011,we collected female and male subadults(gonads have not yet matured),juveniles(tails have just been completely absorbed),and tadpoles(stages 28—38) of the tiger frog Hoplobatrachus chinensis,which is a national secondary grade protection animal,from the herpetological laboratory of Lishui University,Zhejiang,East China.The objectives of this study were to examine ontogenetic shifts in the selected body temperature(Tsel),critical thermal maximum(CTmax),and critical thermal minimum(CTmin) of the tiger frog.Tsel of tadpoles was measured by recording the water temperature of their selected location in a thermal gradient ranging from 10—42℃,while Tsel of juveniles and subadults was measured by recording cloacal temperature in a thermal gradient ranging from 20—45℃.We cooled(for CTmin determination) or heated(for CTmax determination) experimental animals from 25℃.Body temperatures associated with a transient loss of the righting response at lower and upper limits of thermal tolerance were considered to be the endpoints for CTmin and CTmax,respectively.Statistical analysis by ANOVA showed that there were significant differences in Tsel,CTmin,CTmax,and viable temperature range among the three age groups.The Tsel of juveniles(24.10℃) was significantly lower than that of female subadults(28.06℃),male subadults(29.17℃),and tadpoles(28.23℃),while there was no significant difference in Tsel among the latter three groups.The CTmin of juveniles(13.85℃) was significantly higher than that of female subadults(11.27℃),male subadults(10.84℃),and tadpoles(10.74℃),while there was no significant difference in CTmin among the latter three.Tadpoles had the highest CTmax,which was 43.31℃,followed by subadults(female: 39.55℃;male: 39.02℃) and juveniles in decreasing order.Similarly,tadpoles had the widest viable temperature range(32.58℃),followed by subadults(female: 28.28℃;male: 28.18℃),and juveniles(21.62℃) in decreasing order.There were no significant differences in Tsel,CTmin,CTmax,and viable temperature range between female and male subadults.Body temperature of juveniles and subadults of H.chinensis was significantly correlated with water temperature in both decreasing and increasing rates.After removing the effects of water temperature,changes in rates of body temperature variation were removed by using residuals from the regression.Two-way ANOVA(cooling and heating rate were measured repeatedly) indicated that the rates of change in the body temperature of juveniles were significantly greater than rates of change of subadults.Types of thermal changes(i.e.rates of cooling and heating) and the interaction of these factors had no effect on changes in the body temperature of H.chinensis.In conclusion,we suggest that in the tiger frog H.chinensis,fundamental thermal niche separation and development restrictions are the most probable explanations for our findings. |
