Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
Laboratoire Jean Perrin (LJP), Institut de Biologie Paris-Seine (IBPS), Sorbonne Université, CNRS, 4 Place Jussieu, 75005 Paris, France.
Curr Biol. 2021 Feb 22;31(4):782-793.e3. doi: 10.1016/j.cub.2020.11.051. Epub 2020 Dec 17.
Salinity levels constrain the habitable environment of all aquatic organisms. Zebrafish are freshwater fish that cannot tolerate high-salt environments and would therefore benefit from neural mechanisms that enable the navigation of salt gradients to avoid high salinity. Yet zebrafish lack epithelial sodium channels, the primary conduit land animals use to taste sodium. This suggests fish may possess novel, undescribed mechanisms for salt detection. In the present study, we show that zebrafish indeed respond to small temporal increases in salt by reorienting more frequently. Further, we use calcium imaging techniques to identify the olfactory system as the primary sense used for salt detection, and we find that a specific subset of olfactory receptor neurons encodes absolute salinity concentrations by detecting monovalent anions and cations. In summary, our study establishes that zebrafish larvae have the ability to navigate and thus detect salinity gradients and that this is achieved through previously undescribed sensory mechanisms for salt detection.
盐度水平限制了所有水生生物的可居住环境。斑马鱼是淡水鱼，不能耐受高盐环境，因此受益于使它们能够在盐度梯度中导航以避免高盐度的神经机制。然而，斑马鱼缺乏上皮钠通道，而这是陆地动物用来感知钠的主要途径。这表明鱼类可能具有用于盐检测的新颖而未被描述的机制。在本研究中，我们表明，斑马鱼确实通过更频繁地重新定向来对盐度的短暂增加做出反应。此外，我们使用钙成像技术鉴定出嗅觉系统是用于盐检测的主要感觉器官，并且我们发现特定的嗅觉受体神经元亚群通过检测单价阴离子和阳离子来编码绝对盐浓度。总之，我们的研究表明，斑马鱼幼虫具有导航和检测盐度梯度的能力，而这是通过以前未被描述的盐检测感觉机制来实现的。
