Sides and eyes: studies on laterality in anuran larvae

虽然蝌蚪没有手，但它们仍然有惯用手。例如，大多数种类的蝌蚪在受到惊吓时转向左侧的频率是转向右侧的两倍。更奇怪的是，许多种类的蝌蚪（但不是全部）更喜欢用左眼而不是右眼在镜子里看自己。在NSERC的支持下，我计划调查尽可能多的蛙类科和属的蝌蚪的这种“侧化”行为。我的总体目标是了解这些生物中偏侧行为的进化。有间接证据表明，蝌蚪的转向偏向与它们后脑某些细胞大小的不对称有关。为了阐明这种行为与神经之间的联系，我将研究具有强烈侧化行为的物种中这些细胞的大小。然后，我将检验这个假设，即蝌蚪的惯用手性与青蛙的进化关系和它们大脑的不对称性有关。最近有一些数据表明，捕食风险会影响蝌蚪的转向偏好。因此，我计划在几个物种中研究这一点，通过记录蝌蚪在笼养的捕食者（如鱼）附近时的转向倾向。最后，我提出，蝌蚪可能会把自己在镜子中的形象理解为另一只蝌蚪，并对自己的形象做出反应，就好像它们被其他蝌蚪挤在一起一样。在NSERC的支持下，我希望验证这样一个假设，即不同的物种在有镜像墙的水族箱中会以不同的速度生长，这取决于它们在密集群体中生活的倾向（即，去学校）。总的来说，这项研究将促进我们对无尾动物和其他动物的侧向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.