外来捕食者克氏原螯虾对黑斑侧褶蛙不同发育阶段幼体表型与运动能力的影响

外来物种入侵是造成本土无尾两栖类种群下降和灭绝的最严重威胁之一。在中国南部丽水地区,克氏原螯虾(Procambarus clarkiion)是一种捕食本土无尾类蝌蚪的入侵物种。在实验室条件下,通过对黑斑侧褶蛙(Pelophylax nigromaculatus)受精卵和蝌蚪先后进行克氏原螯虾捕食风险的不同处理,检测孵出蝌蚪的形态特征、中期蝌蚪的形态特征、游泳表现及活动水平、变态时间与大小以及幼蛙跳跃表现,评估克氏原螯虾的捕食风险对黑斑侧褶蛙不同生长阶段幼体生长发育、运动能力及行为的综合影响。单因素方差分析表明,捕食者长期存在条件下黑斑侧褶蛙孵出蝌蚪的体长、尾长和尾肌宽均显著短于无捕食者的空白对照组和捕食者仅存在2 d的实验组,后两者处理下的蝌蚪体长差异显著,但尾长和尾肌宽差异不显著。长期捕食者存在条件下黑斑侧褶蛙蝌蚪的游泳总路程和平均游速均显著小于无捕食者和捕食者存在2 d的实验组,而蝌蚪体长、尾长、尾鳍高和尾肌高的组间差异均不显著。有捕食者存在下黑斑侧褶幼蛙的体长和体重均显著大于无捕食者和捕食者存在2 d的实验组的情况,而变态时间和幼蛙跳跃距离组间差异不显著。两因素方差分析表明,测试时间、捕食者设置和两因素的相互作用均显著影响蝌蚪的活动频次。不同实验时间,长期捕食者存在实验组蝌蚪活动频次均小于无捕食者和捕食者存在2 d的实验组。无捕食者实验组蝌蚪的活动频次前期高于捕食者存在2 d的实验组,后期低于捕食者存在2 d的实验组。线性回归分析结果显示,捕食者存在2 d实验组蝌蚪相对活动频次与检测时间相关不显著,长期捕食者存在实验组相对蝌蚪活动频次与检测时间呈显著的正相关。本研究表明了黑斑侧褶蛙蝌蚪能够感知来自入侵捕食者克氏原螯虾的捕食风险,诱导产生较小的孵出个体、蝌蚪较低的活动水平,但这种不足可通过后期补偿生长,不影响进入陆地生境的变态个体的表型与运动能力。

Effects of exotic predator Procambarus clarkiion on the phenotype and performance of Pelophylax nigromaculatus Larva

Alien species is one of the most serious threats causing the decline and extinction of native anuran populations. Procambarus clarkiion is an exotic invader which can predate egg and tadpoles of anuran in Lishui, Zhejiang, south China. Under laboratory conditions, the eggs and tadpoles of Pelophylax nigromaculatus were successively exposed to different predation risk from P. clarkiion including none (no-predator), caged for two days (transient-predator) and caged for all days (permanent-predator). We measured the phenotype of hatchlings, morphological characteristics, swimming performance and activity level of tadpoles, age and size at metamorphosis, body size and jumping performance of juveniles in P. nigromaculatus. We aimed to assess the comprehensive effects of the predator P. clarkiion on the growth and development, locomotor performance and behavior of P. nigromaculatus larvas. One-way ANOVA and Tukey''s post hoc test indicated that body length, tail fin length, and tail muscle width of the hatchlings in permanent-predator treatment were significantly shorter than those tadpoles in the no- and transient-predator treatments. Moreover, the tadpoles in no-predator groups were larger than those in the transient-predator treatments, although their tail fin phenotypes were almost similar. The tadpoles in the permanent-predator treatments can swim averagely longer and quicker than those in the no- and transient-predator treatments, but their sprint speed swimming were almost alike. There were no significant differences for the body length, tail length, tail fin height, tail muscle height of the tadpoles among groups. The snout-vent length and body mass of the P. nigromaculatus juveniles in the permanent-predator treatments were significantly longer than ones of the latter two treatments, but the risk of predation had no significant effect on the metamorphosis time and jump distances. Two-way ANOVA and Tukey''s post hoc test indicated that testing time, predator and their interactions significantly affected the activity state of the tadpoles. There were lesser active tadpoles in permanent-predator treatments than those in no- and transient-predator treatments. The tadpoles in no-risk treatments were more active than those in the transient-predator treatments during the early stage of the experiment, while the results were reverse in the final stage of the experiment. The linear-regression analysis revealed that there were no significant correlation between testing time and activity level of the transient-predator tadpoles, but activity frequency of permanent-predator tadpoles were significantly and positively correlated with testing time. The study demonstrates that P. nigromaculatus tadpoles can sense predation risk from invasive predator crayfish. The predator risk induce the smaller hatchlings and lower activity level of tadpoles, but the negative effects can be offset by the compensation growth of tadpoles during the subsequent development. Therefore, it does not affect the phenotype and locomotor performance of juvenile entering the terrestrial habitats.