Abstract：
For organisms tracking a chemical cue to its source, the motion of their surrounding fluid provides crucial information for success. Swimming and flying animals engaged in olfaction-driven search often start by turning into the direction of an oncoming wind or water current. However, it is unclear how organisms adjust their strategies when directional cues are absent or unreliable, as is often the case in nature. Here, we use the genetic toolkit of Drosophila melanogaster to develop an optogenetic paradigm to deliver temporally precise \"virtual\" olfactory experiences for free-flying animals in either laminar wind or still air. We first confirm that in laminar wind flies turn upwind. Furthermore, we show that they achieve this using a rapid (∼100 ms) turn, implying that flies estimate the ambient wind direction prior to \"surging\" upwind. In still air, flies adopt a remarkably stereotyped \"sink and circle\" search state characterized by ∼60° turns at 3-4 Hz, biased in a consistent direction. Together, our results show that Drosophila melanogaster assesses the presence and direction of ambient wind prior to deploying a distinct search strategy. In both laminar wind and still air, immediately after odor onset, flies decelerate and often perform a rapid turn. Both maneuvers are consistent with predictions from recent control theoretic analyses for how insects may estimate properties of wind while in flight. We suggest that flies may use their deceleration and \"anemometric\" turn as active sensing maneuvers to rapidly gauge properties of their wind environment before initiating a proximal or upwind search routine.
摘要：
对于追踪化学线索的生物，它们周围液体的运动为成功提供了关键信息。从事嗅觉驱动搜索的游泳和飞行动物通常从转向迎面而来的风或水流的方向开始。然而,目前还不清楚，当方向线索缺失或不可靠时，生物体如何调整策略，就像自然界中经常发生的那样。这里,我们使用果蝇的遗传工具包来开发光遗传学范式，以在层流风或静止空气中为自由飞行的动物提供时间上精确的“虚拟”嗅觉体验。我们首先确认在层流风中苍蝇逆风。此外，我们表明，他们使用快速(~100毫秒)转弯来实现这一目标，暗示苍蝇在“汹涌”逆风之前估计环境风向。在静止的空气中，苍蝇采用一种非常刻板的“下沉和圆圈”搜索状态，其特征是在3-4赫兹时达到60°转弯，偏向一致的方向。一起,我们的结果表明，果蝇在部署独特的搜索策略之前会评估环境风的存在和方向。在层流和静止空气中，气味发作后立即，苍蝇减速并经常快速转弯。两种操作都与最近的控制理论分析有关昆虫如何在飞行中估计风的特性的预测一致。我们建议苍蝇可以使用减速和“风速测量”作为主动感测动作，以在启动近端或迎风搜索程序之前快速测量其风环境的属性。
