无尾类两栖动物蝌蚪对食蚊鱼的行为和生理响应

Evaluating the impacts of invasive species on diversity of native species is a central goal of ecology. Once found only in North America, mosquitofish (Gambusia affinis) have been introduced into ecosystems in many parts of the world as a biocontrol to lower mosquito populations but have also entailed a number of negative effects on many native species in each distinct bioregion. Introductions outside the fish's natural range often are harmful to the nonnative ecosystems. The fish has been listed as one of 100 most threatened invasive species in the world. As in many other parts of the world, mosquitofish are considered noxious pests in China where they pose a threat to native fish and frog populations but, unfortunately, empirical studies conducted in China to examine the fish's impacts on diversity of native anuran species have been scarce. Here, we will study behavioral and physiological responses of anuran tadpoles to the invasive mosquitofish G. affinis by comparing anti-predator behaviors, phenotypic traits and hormonal (corticosterone) levels between treatments with tadpoles undergoing and not undergoing exposure to mosquitofish. More specifically, we will use tadpoles of nine anuran species (Bufo gargarizans, Duttaphrynus melanostictus, Fejervarya multistriata, Hoplobatrachus rugulosa, Hylarana guentheri, Microhyla onata, Pelophylax nigromaculatus, Polypedates megacephalus and Rana zhenhaiensis) most commonly found in Lishui but differing in breeding season as model systems to examine (1) differences in activity level before and after exposure of tadpoles to predatory chemical cue, and (2) differences in anti-predator behavior, phenotypic response and locomotor performance among tadpoles exposed to different predators. Tadpoles of the nine anuran species will be also used to evaluate the time period needed to establish adaptive responses to mosquitofish. By manipulating the growth rate (of tadpoles) for one week, we will examine the potential effects of body size and growth rate of tadpoles on predator memory retrieval window for recognizing mosquitofish. We will try to uncover the underlying neuroendocrinological basis to anti-predator freezing behavior by comparing corticosterone levels before and after exposure of tadpoles to predation risks. Data generated from this study will allow us draw some general conclusions on behavioral and physiological responses of anuran tadpoles to mosquitofish.

评估外来种对入侵地物种多样性的影响是生态学领域的重要课题。原产北美的食蚊鱼是全球100种最具威胁性的外来入侵物种之一，对入侵地的无尾两栖类多样性造成严重的威胁，但其对我国无尾类多样性的危害还未有深入的研究。申请人拟观察暴露和非暴露于食蚊鱼的蝌蚪行为、测定其表型变异和激素水平变化等，研究无尾类蝌蚪对食蚊鱼的行为与生理响应。拟在丽水采集9种繁殖期不同的无尾类蝌蚪，记录分别暴露在捕食信号刺激前后的活动水平变化，检测蝌蚪对不同来源捕食者诱导所产生的反捕行为响应差异；通过蝌蚪与关在笼内捕食者的混养实验，收集表型响应及其运动表现差异数据，评估蝌蚪对入侵食蚊鱼的适应性响应所需时间；通过让蝌蚪保持缓慢和快速生长1周后对捕食风险刺激的反捕行为响应变化，检测蝌蚪个体大小与生长速率对蝌蚪识别食蚊鱼的记忆检索窗口的潜在影响；通过蝌蚪在遭遇捕食风险前后的肾上腺酮水平分析，阐明蝌蚪反捕行为抑制的神经内分泌机制。

评估外来种对入侵地物种多样性的影响是生态学领域的重要课题。原产北美的食蚊鱼是全球100种最具威胁性的外来入侵物种之一，对入侵地的无尾两栖类多样性造成严重的威胁，但 其对我国无尾类多样性的危害还未有深入的研究。本项目通过观察暴露和非暴露于捕食者食蚊鱼的蝌蚪行为、测定其表型变异和激素水平变化等，研究无尾类蝌蚪对食蚊鱼的行为及生理响应。项目拟在丽水采集不同繁殖期的无尾类蝌蚪，记录分别暴露在捕食信号刺激前后的活动水平变化，检测蝌蚪对不同来源捕食者诱导所产生的反捕行为响应差异；通过蝌蚪与关在笼内捕食者的混 养实验，收集表型响应及其运动表现差异数据，评估蝌蚪对入侵食蚊鱼的适应性响应所需时间 ；通过让蝌蚪保持缓慢和快速生长1周后对捕食风险刺激的反捕行为响应变化，检测蝌蚪个体 大小与生长速率对蝌蚪识别食蚊鱼的记忆检索窗口的潜在影响；通过蝌蚪在遭遇捕食风险后 的肾上腺酮水平分析，阐明蝌蚪反捕行为抑制的神经内分泌机制。研究结果表明：食蚊鱼捕食无尾类的受精卵、胚胎和蝌蚪具有物种特异性。蟾蜍类蝌蚪对食蚊鱼的脆弱性低于蛙类蝌蚪，蝌蚪基本采取降低活动与远离食蚊鱼的反捕行为。当食蚊鱼对黑斑侧褶蛙蝌蚪的尾鳍伤害超过一半时，会对其疾游速产生消极影响；当捕食压力移除后，黑斑侧褶蛙蝌蚪可通过补偿生长对尾鳍进行修复，且不会影响变态时间与大小。食蚊鱼存在下，斑腿树蛙孵出较小个体，但形成较大变态个体，降低活动水平，减弱游泳耐力，变态时间与跳跃距离不受影响。食蚊鱼对虎纹蛙和泽陆蛙幼体生长发育、变态时间与大小，运动能力及反捕行为的影响也表现出物种特异性。生长较快的蝌蚪能更快地识别捕食风险。食蚊鱼刺激液和同种受伤个体示警液处理下的蝌蚪会提高肾上腺酮水平。