Sides and eyes: studies on laterality in anuran larvae

虽然小蝌蚪没有手，但它们仍然可以用手。例如，大多数物种的蝌蚪在受到惊吓时，向左侧转动的频率通常是向右侧转动的两倍。更奇怪的是，许多物种的蝌蚪(但不是所有物种)更喜欢用左眼而不是右眼看镜子中的自己。在NSERC的支持下，我计划调查尽可能多的青蛙科和属的小蝌蚪的这种“偏侧化”行为。我的总体目标是了解这些生物的偏侧化行为的进化。但有间接证据表明，蝌蚪的偏向与它们后脑中某些细胞的大小不对称有关。为了阐明这种行为-神经联系，我将研究具有强烈偏侧化行为的物种中这些细胞的大小。然后，我将检验这一假设，即蝌蚪的惯用手与青蛙的进化关系和它们大脑的不对称性都相关。但最近的一些数据表明，捕食风险影响了蝌蚪的转向偏向。因此，我计划在几个物种中研究这一点，方法是记录蝌蚪在笼子里的捕食者(如鱼)在附近时的转向偏向。最后，我建议蝌蚪可能会将自己在镜子中的形象解读为另一只蝌蚪，并像被其他蝌蚪挤在一起一样对自己的形象做出反应。在NSERC的支持下，我希望测试这一假说，即不同物种在有镜墙的水族箱中饲养时，根据它们聚集在一起(即上学)的倾向，将以不同的速度生长。因此，总的来说，这项研究应该促进我们对无尾两栖动物和其他动物偏侧化行为的适应意义和进化的理解。

Although they don't have hands, tadpoles can nevertheless have handedness. For instance, tadpoles of most species typically turn about twice as often to their left than their right side when startled. Even more curious, tadpoles of many species (but not all) prefer to view themselves in mirrors with their left eye rather than their right. With NSERC support I plan to survey such "lateralized" behaviors from tadpoles of as many families and genera of frogs as possible. My overall goal is to understand the evolution of lateralized behaviors in these organisms.  There is circumstantial evidence that turning bias in tadpoles is linked to asymmetry in the size of certain cells in their hindbrains. In order to elucidate this behavioural-neural link, I will examine the size of those cells in species with strongly lateralized behaviors. I will then test the hypothesis that handedness in tadpoles correlates with both the evolutionary relationships of the frogs and asymmetries in their brains.  There are some recent data suggesting that predation risk influenced tadpole turning bias. I thus plan to investigate this in several species by recording tadpoles' turning biases while caged predators, such as fish, are nearby.  Lastly, I have suggested that tadpoles might interpret their own image in a mirror as another tadpole and respond to their images as if they were crowded by other tadpoles. With NSERC support, I wish to test the hypothesis that different species will grow at different rates when raised in aquaria with mirrored walls depending on their propensity to live in dense groups (i.e., to school).      Collectively this research should advance our understanding of the adaptive significance and evolution of lateralized behaviours in anurans and in other animals as well.