McCullagh Gregory B, Bishop Cory D, Wyeth Russell C
Department of Biology, St Francis Xavier University, PO Box 5000 Antigonish, NS, Canada B2G 2W5.
Department of Biology, St Francis Xavier University, PO Box 5000 Antigonish, NS, Canada B2G 2W5
J Exp Biol. 2014 Dec 1;217(Pt 23):4149-58. doi: 10.1242/jeb.111153. Epub 2014 Oct 16.
Tritonia diomedea (synonymous with Tritonia tetraquetra) navigates in turbulent odour plumes, crawling upstream towards prey and downstream to avoid predators. This is probably accomplished by odour-gated rheotaxis, but other possibilities have not been excluded. Our goal was to test whether T. diomedea uses odour-gated rheotaxis and to simultaneously determine which of the cephalic sensory organs (rhinophores and oral veil) are required for navigation. In a first experiment, slugs showed no coherent responses to streams of odour directed at single rhinophores. In a second experiment, navigation in prey and predator odour plumes was compared between animals with unilateral rhinophore lesions, denervated oral veils, or combined unilateral rhinophore lesions and denervated oral veils. In all treatments, animals navigated in a similar manner to that of control and sham-operated animals, indicating that a single rhinophore provides sufficient sensory input for navigation (assuming that a distributed flow measurement system would also be affected by the denervations). Amongst various potential navigational strategies, only odour-gated positive rheotaxis can produce the navigation tracks we observed in prey plumes while receiving input from a single sensor. Thus, we provide strong evidence that T. diomedea uses odour-gated rheotaxis in attractive odour plumes, with odours and flow detected by the rhinophores. In predator plumes, slugs turned downstream to varying degrees rather than orienting directly downstream for crawling, resulting in greater dispersion for negative rheotaxis in aversive plumes. These conclusions are the first explicit confirmation of odour-gated rheotaxis as a navigational strategy in gastropods and are also a foundation for exploring the neural circuits that mediate odour-gated rheotaxis.
多角三歧海牛（与四角三歧海牛同义）在湍急的气味羽流中导航，向上游爬行以靠近猎物，向下游爬行以躲避捕食者。这可能是通过气味门控趋流性实现的，但其他可能性也未被排除。我们的目标是测试多角三歧海牛是否使用气味门控趋流性，并同时确定在导航过程中需要哪些头部感觉器官（嗅角和口膜）。在第一个实验中，海蛞蝓对指向单个嗅角的气味流没有一致的反应。在第二个实验中，比较了单侧嗅角损伤、口膜去神经支配或单侧嗅角损伤与口膜去神经支配相结合的动物在猎物和捕食者气味羽流中的导航情况。在所有处理中，动物的导航方式与对照动物和假手术动物相似，这表明单个嗅角为导航提供了足够的感官输入（假设分布式流量测量系统也会受到去神经支配的影响）。在各种潜在的导航策略中，只有气味门控正向趋流性在从单个传感器接收输入时，才能产生我们在猎物羽流中观察到的导航轨迹。因此，我们提供了有力证据，证明多角三歧海牛在有吸引力的气味羽流中使用气味门控趋流性，气味和水流由嗅角检测。在捕食者羽流中，海蛞蝓不同程度地转向下游，而不是直接向下游定向爬行，导致在厌恶羽流中负向趋流性的分散性更大。这些结论首次明确证实了气味门控趋流性是腹足纲动物的一种导航策略，也是探索介导气味门控趋流性的神经回路的基础。
