Hitchhikers (phoretic organisms) need vehicles to disperse out of unsuitable habitats. Therefore, finding vehicles with the right functional attributes is essential for phoretic organisms. To locate these vehicles, phoretic organisms employ cues within modalities, ranging from visual to chemical senses. However, how hitchhikers discriminate between individual vehicles has rarely been investigated. Using a phoretic nematode community associated with an obligate fig–fig wasp pollination mutualism, we had earlier established that hitchhiking nematodes make decisions based on vehicle species identity and number of conspecific hitchhikers already present on the vehicle. Here we investigate if hitchhikers can differentiate between physiological states of vehicles. We asked whether phoretic nematodes choose between live or dead vehicles present in a chemically crowded environment and we investigated the basis for any discrimination. We conducted two-choice and single-choice behavioral assays using single nematodes and found that plant- and animal-parasitic nematodes preferred live over dead vehicles and used volatiles as a sensory cue to make this decision. However, in single-choice assays, animal-parasitic nematodes were also attracted towards naturally dead or freeze-killed wasps. The volatile profile of the wasps was dominated by terpenes and spiroketals. We examined the volatile blend emitted by the different wasp physiological states and determined a set of volatiles that the phoretic nematodes might use to discriminate between these states which is likely coupled with respired CO₂. We determined that CO₂ levels emitted by single wasps are sufficient to attract nematodes, demonstrating the high sensitivity of nematodes to this metabolic product.

旅行者（隐喻生物）需要借助车辆才能散布到不合适的栖息地中。因此，寻找具有正确功能属性的载体对于电泳生物至关重要。为了定位这些载体，隐喻生物利用从视觉到化学感觉的各种形式的线索。但是，很少有人研究旅行者如何区分各个车辆。使用与专性无花果-蜂黄蜂授粉共生相关的隐线虫群落，我们较早地确定了搭便车线虫是根据车辆种类的身份和已经存在于车辆上的同种搭便车者的数量做出决定的。在这里，我们调查旅行者是否可以区分车辆的生理状态。我们询问了幽灵线虫是否在化学拥挤的环境中存在的生的或死的载具之间进行选择，并且我们调查了任何辨别的依据。我们使用单个线虫进行了两种选择和单项行为分析，发现动植物和线虫寄生的线虫比活的线虫更喜欢活体，并使用挥发物作为感官提示做出此决定。但是，在单选分析中，动物寄生线虫也被吸引到自然死亡或冻死的黄蜂。黄蜂的挥发性特征主要是萜烯和螺环草。我们检查了由不同的黄蜂生理状态释放的挥发性混合物，并确定了隐影线虫可能用来区分这些状态的一组挥发性物质，这很可能与呼吸的一氧化碳有关。₂。我们确定单个黄蜂排放的CO ₂水平足以吸引线虫，这表明线虫对此代谢产物具有高度敏感性。