The sensory biology of swim bladder inflation in larval zebrafish.

点击翻译按钮获取中文摘要

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.