The sensory biology of swim bladder inflation in larval zebrafish.

在鱼类从被动胚胎过渡到自由游动幼体的过程中，鱼囊的膨胀是生命中的一个重要里程碑。SB是一个充满气体的器官，允许鱼类调节它们在水柱中的位置。许多种类的鱼通过吞食水面上的空气来引发SB充气，这种行为我们称之为“浮出水面”。为了成功地使其SBS膨胀，幼鱼必须能够定位表面并区分水和空气的物理性质。通常，SB膨胀必须在幼虫发育的短暂窗口开始。在这一关键时期不充气导致幼体死亡率高，是水产养殖业和观赏鱼贸易遭受重大损失的原因。尽管SB膨胀的重要性得到了公认，但描绘关键期的生理机制尚不清楚，幼虫死亡的原因也不确定，我们对表面行为的感官基础缺乏详细的了解。在这里，我建议使用斑马鱼模型系统来解决我们知识中的这些差距。具体地说，这个项目将：1)确定斑马鱼幼体Sb膨胀的关键期，并描述异常充气的生理后果；2)测试表面张力和粘度等水动力信号如何影响幼虫的表面行为；3)确定幼虫如何结合水动力和光感官信号来执行它们的表面行为。这项工作结合了斑马鱼遗传学的力量和对幼虫饲养环境的实验操作，以确定浮出水面和SB膨胀的感官基础。这项工作的创新之处来自于我之前对感觉毛细胞功能的分子遗传学的研究。利用CRISPR-Cas基因组编辑，我创造了第一个专门沉默机械感觉侧线的基因突变。机械感觉侧线是水生脊椎动物的感官器官，可以检测水的运动等水动力信号。这个突变体天生“对水耳聋”，代表了第一个了解侧线器官如何影响幼鱼在过渡到幼体阶段时的行为的模型。引人注目的是，我们对这个突变的观察提供了第一个证据，证明幼鱼使用水动力学信息来指导它们的浮出水面的行为。这项工作有可能彻底改变我们对侧线和幼虫表面行为的理解。更好地了解初级SB通胀将有助于水产养殖业为商业性养鱼创造更有利的条件。我们工作的影响还将延伸到鱼类生理学和神经生物学领域。最后，这项工作将使学生参与一个综合研究计划，解决动物行为的遗传基础。

Inflation of the swim bladder (SB) is a major milestone in the life of fish as they transition from passive embryos to free-swimming larvae. The SB is a gas-filled organ that allows fish to regulate their position in the water column. Many species of fish initiate SB inflation by gulping air from the surface in a behavior we refer to as "surfacing". To successfully inflate their SBs, larval fish must be able to locate the surface and distinguish between the physical properties of water and air. Typically, SB inflation must be initiated during a brief window of larval development. Failure to inflate during this critical period results in high rates of larval mortality and is the cause of significant losses to the aquaculture and ornamental fish trade industries. Despite the recognized importance of SB inflation, the physiological mechanisms that delineate the critical period are not clear, the causes of larval mortality are uncertain, and we lack a detailed understanding of the sensory basis for the surfacing behaviour. Here, I am proposing to address these gaps in our knowledge using the zebrafish model system. Specifically, this project will: 1) define the critical period for SB inflation in larval zebrafish and describe the physiological consequences of abnormal inflation; 2) test how hydrodynamic cues like surface tension and viscosity affect the larval surfacing behaviour; and 3) establish how larvae integrate hydrodynamic and photosensory cues to perform their surfacing behaviors. This work combines the power of zebrafish genetics with experimental manipulations of the larval rearing environment to define the sensory basis for surfacing and SB inflation. The innovative aspect of this work comes out of my previous studies on the molecular genetics of sensory hair cell function. Using CRISPR-Cas genome editing, I have created the first genetic mutant that specifically silences the mechanosensory lateral line - the sensory organ in aquatic vertebrates that detects hydrodynamic cues like water motion. This mutant is born "deaf to water" and represents the first model to understand how the lateral line organ influences the behaviours of baby fish as they make the transition into larval stages. Strikingly, our observations of this mutant have provided the first evidence that larval fish use hydrodynamic information to instruct their surfacing behaviours. This work has the potential to revolutionize our understanding of the lateral line and the larval surfacing behaviour. A better understanding of primary SB inflation will assist the aquaculture industry in developing more favorable conditions for commercial fish rearing. The impact of our work will also extend into the fields of fish physiology and neurobiology. Lastly, this work will engage students in an integrative research program that addresses the genetic basis of animal behaviour.