A Comparison Of Pawning Site Selection And Tadpole Traits Between Bufo Gargarizans And Rana Zhenhaiensis From Lishui, Zhejiang

In this dissertation, I mainly studied four aspects of two anuran species in Lishui, Zhejiang province. The details were as follows:(1) the traits and differences of spawning sites selected by Bufo gargarizans and Rana zhenhaiensis;(2) the effects of tail loss on swimming performance and survival rate in tadpoles of B. gargarizans and R. zhenhaiensis;(3) morphological correlates of swimming ability and the effects of temperature and developmental stage on swimming performance in tadpoles of B. gargarizans and R. zhenhaiensis;(4) activity level response to light intensity in tadpoles of B. gargarizans and R. zhenhaiensis. The main conclusions and results are summarized as following:1. A comparison of spawning site selection between Bufo gargarizans and Rana zhenhaiensisI used two species of amphibian, Bufo gargarizans and Rana zhenhaiensis, as the model animals to study whether the two sympatric anurans showed differences in spawning-site preference and whether biotic and abiotic factors differed between water bodies used and not used as spawning sites. Results of one-way ANOVA showed that water bodies used and not used as spawning sites did not differ in any examined factors in B. gargarizans. Results ofx2-test showed that B. gargarizans only spawn in still water, natural and permanent waterbodies or artificial and temporary water bodies had no significant effect on spawning site selection; the presence of other species (both potential competitors and predators) did not appear to influence spawning sites selection by B. gargarizans. Results of one-way ANOVA showed that the distance to the nearest road, size of the water, water depth, the proportion of open ground surrounding the waterbody and water chemistry were not significant between spawning sites and non-spawning sites in R. zhenhaiensis; the water shore slope in spawning sites was significant smaller than that of non-spawning sites, the proportion of vegetation covering the water surface in spawning sites was significant smaller than that of non-spawning sites. Result of x2-test showed that R. zhenhaiensis displayed a clear preference for oviposition in still, natural and temporary waterbodies, and no other species (both potential competitors and predators). Results of one-way ANOVA showed that water depth had significant effect on spawning sites selection, the water depth of spawning sites used by B. gargarizans was significantly deeper than R. zhenhaiensis; other environmental variables and water chemistry did not differ between the two species. Results of x2-test showed that artificial or natural water, permanent or temporary water, and the presence of other species (both potential competitors and predators) significantly affected the spawning site selection of B. gargarizans and R. zhenhaiensis. B. gargarizans only spawn in still water, while R. zhenhaiensis displayed a clear preference for oviposition in still, natural, temporary and no other species water bodies.2. The effects of tail loss on swimming performance and survival rate of tadpoles in two sympatric anuran species, Bufo gargarizans and Rana zhenhaiensisThe results of morphological variables and developmental stage measured for tadpoles of B. gargarizans and R. zhenhaiensis used to examine the effect of tail loss on swimming performance showed that mean values for developmental stage did not differ between the two species, nor between experimental group and control group, but for SVL of larval B. gargarizans was significantly smaller than that of larval R. zhenhaiensis. After removing the effect of snout-vent length (SVL), tail length and body mass were significantly smaller in larval of B. gargarizans than in larval R. zhenhaiensis. The results of linear regression analysis for experimental group showed that number of stops was negatively related to SVL, while maximal distance and swimming speed were positively related to SVL. We used three-way ANCOVA with SVL as the covariate to examine whether swimming performance differed between the two species, between experimental group and control group, and between intact tail group and50%degree of tail loss group. The results showed that:(1) swimming speed of B. gargarizans tadpoles were significantly smaller than that of R. zhenhaiensis in the first test;(2) number of stops and maximal distance were not significant between the two species;(3) number of stops before tail loss was significantly less than that of after tail loss, while maximal distance and swimming speed were significantly more than that of after tail loss; and (4) number of stops in control group was significantly less than that in experimental group, but maximal distance and swimming speed were significantly more than experimental group. After50%tail loss, swimming speed and maximal distance of the tadpoles of B. gargarizans and R. zhenhaiensis were decreased significantly. All of the B. gargarizans tadpoles after75%tail loss could not swim, while15%of R. zhenhaiensis tadpoles could swim after75%tail loss. It showed that high degree of tail loss has an important effect on swimming performance in anuran tadpoles. Besides, there were6B. gargarizans tadpoles dead in experimental group after50%tail loss, and the mortality rate was31.58%, while there were no R. zhenhaiensis tadpole dead in experimental group for the two artificial tail loss, and tail loss had a significant effect on mortality for the two species tadpoles. We infer that the sympatric tadpoles (B. gargarizans and R. zhenhaiensis) may face the same predator pressure and form different ways to adapt.3. Morphological correlates of swimming ability and the effect of temperature and developmental stage on swimming performance of tadpoles in Bufo gargarizans and Rana zhenhaiensisA two-factor experiment was carried out to determine the effects of temperature and developmental stage on swimming performance in B. gargarizans and R. zhenhaiensis tadpoles. I also measured the relationship of morphological traits and swimming performance. The results of morphological variables measured for tadpoles of B. gargarizans and R. zhenhaiensis showed that SVL was not significantly different between the two species and increased significantly from earlier developmental stage to later for both species. The interaction between species and developmental stages has significant effect on SVL. After removing the effect of SVL, we found that:(1) the tail length, tail depth and body mass were significantly smaller in tadpoles of B. gargarizans than in R. zhenhaiensis, whereas body width was significantly greater in B. gargarizans than in R. zhenhaiensis, however tail muscle depth at the base and tail area had no significant difference between the two species;(2) body width was significantly different between different developmental stages, the difference of other morphological traits (tail length, tail depth, tail muscle depth at the base, tail area and body mass)were not significant;(3) both tail depth and body width were significantly affected by the species x developmental stage interaction, whereas the other traits measured were not. The results of swimming performance showed that number of stops was significantly affected by temperature, and in low temperature (15℃20℃) it was significantly less than that in high temperature (25℃. In addition, the species x temperature interaction had no effect on number of stops, yet the remaining interactions among the three factors (species, temperature and developmental stages) had significant effect on number of stops. Maximal distance did not differ between the two species, nor among the temperatures; however, it was significantly affected by the species x developmental stages interaction and the species x temperature x developmental stages interaction. Swimming speed was different between the two species, but was not affected by temperature and developmental stages. The interactions among the three factors had no effect on swimming speed.4. The effect of light intensity on activity level in tadpoles of Bufo gargarizans and Rana zhenhaiensisThe developmental stage of tadpoles used in this experiment was not differed between the two species; however SVL, tail length and body mass of B. gargarizans tadpoles were significantly smaller than that of R. zhenhaiensis. The results of two-way ANOVA showed that species and light conditions both had no effect on activity level for both species tadpoles, however the interaction had significant effect on activity level. To expound the reason for significant interaction, we tested the activity level for each species in different light conditions and for both species in each light conditions respectively. The results showed that:in high light intensity, the activity level of B. gargarizans tadpoles was significantly higher than that of R. zhenhaiensis tadpoles; however, in low light intensity, the activity level of B. gargarizans tadpoles was significantly lower than R. zhenhaiensis tadpoles. Besides, light intensity has an important effect on activity level for both species tadpoles:the activity level of B. gargarizans tadpoles in high light intensity was significantly higher than in low light intensity, while R. zhenhaiensis tadpoles were more active in low light intensity than in high light intensity. We infer that these results may due to the unpalatable to predators in B. gargarizans tadpoles, thus the predation risk was decreased. For this, B. gargarizans tadpoles took food actively and had high activity level.