National Great Rivers Research and Education Center, East Alton, IL 62024, USA.
Department of Biology, Washington University of St Louis, St Louis, MO 63130, USA.
Proc Biol Sci. 2019 Sep 25;286(1911):20191610. doi: 10.1098/rspb.2019.1610.
Movement enables mobile organisms to respond to local environmental conditions and is driven by a combination of external and internal factors operating at multiple scales. Here, we explored how resource distribution interacted with the internal state of organisms to drive patterns of movement. Specifically, we tracked snail movements on experimental landscapes where resource (algal biofilm) distribution varied from 0 to 100% coverage and quantified how that movement changed over a 24 h period. Resource distribution strongly affected snail movement. Trajectories were tortuous (i.e. Brownian-like) within resource patches but straighter (i.e. Lévy) in resource-free (bare) patches. The average snail speed was slower in resource patches, where snails spent most of their time. Different patterns of movement between resource and bare patches explained movement at larger spatial scales; movement was ballistic-like Lévy in resource-free landscapes, Lévy in landscapes with intermediate resource coverage and approximated Brownian in landscapes covered in resources. Our temporal analysis revealed that movement patterns changed predictably for snails that satiated their hunger and then performed other behaviours. These changes in movement patterns through time were similar across all treatments that contained resources. Thus, external and internal factors interacted to shape the inherently flexible movement of these snails.
运动使移动生物能够对局部环境条件做出反应，其驱动力来自于多个尺度上的外部和内部因素的组合。在这里，我们探讨了资源分布如何与生物体的内部状态相互作用，从而驱动运动模式。具体来说，我们在实验景观上追踪了蜗牛的运动，其中资源（藻类生物膜）的分布从 0%到 100%不等，并量化了在 24 小时内运动的变化。资源分布强烈影响蜗牛的运动。在有资源的斑块内，轨迹是曲折的（即布朗型），而在没有资源的斑块（裸露斑块）内，轨迹是更直的（即莱维型）。在资源斑块中，蜗牛的平均速度较慢，因为它们大部分时间都在那里。资源和裸露斑块之间不同的运动模式解释了更大空间尺度上的运动；在无资源的景观中，运动呈弹道型莱维，在具有中等资源覆盖的景观中呈莱维，在被资源覆盖的景观中呈布朗型。我们的时间分析表明，对于已经满足饥饿感然后执行其他行为的蜗牛，运动模式可以预测性地改变。在所有包含资源的处理中，这些运动模式的变化在时间上是相似的。因此，外部和内部因素相互作用，塑造了这些蜗牛固有的灵活运动。
