Functional and Evolutionary Entomology, Gembloux Agro-Bio Tech, University of Liege, Gembloux, Belgium.
PLoS One. 2011;6(7):e21927. doi: 10.1371/journal.pone.0021927. Epub 2011 Jul 20.
Earthworms are key components of temperate soil ecosystems but key aspects of their ecology remain unexamined. Here we elucidate the role of olfactory cues in earthworm attraction to food sources and document specific chemical cues that attract Eisenia fetida to the soil fungi Geotrichum candidum. Fungi and other microorganisms are major sources of volatile emissions in soil ecosystems as well as primary food sources for earthworms, suggesting the likelihood that earthworms might profitably use olfactory cues to guide foraging behavior. Moreover, previous studies have documented earthworm movement toward microbial food sources. But, the specific olfactory cues responsible for earthworm attraction have not previously been identified. Using olfactometer assays combined with chemical analyses (GC-MS), we documented the attraction of E. fetida individuals to filtrate derived from G. candidum colonies and to two individual compounds tested in isolation: ethyl pentanoate and ethyl hexanoate. Attraction at a distance was observed when barriers prevented the worms from reaching the target stimuli, confirming the role of volatile cues. These findings enhance our understanding of the mechanisms underlying key trophic interactions in soil ecosystems and have potential implications for the extraction and collection of earthworms in vermiculture and other applied activities.
蚯蚓是温带土壤生态系统的关键组成部分，但它们的生态学的关键方面仍未被研究。在这里，我们阐明了嗅觉线索在蚯蚓对食物源的吸引力中的作用，并记录了特定的化学线索，这些线索吸引赤子爱胜蚓（Eisenia fetida）到土壤真菌地霉（Geotrichum candidum）。真菌和其他微生物是土壤生态系统中挥发性排放的主要来源，也是蚯蚓的主要食物来源，这表明蚯蚓可能会利用嗅觉线索来指导觅食行为。此外，先前的研究已经记录了蚯蚓向微生物食物源的运动。但是，负责蚯蚓吸引力的特定嗅觉线索以前尚未确定。我们使用嗅觉计测定与化学分析（GC-MS）相结合，记录了赤子爱胜蚓个体对来自地霉菌落的滤液和两种单独测试的化合物的吸引力：戊酸乙酯和己酸乙酯。当障碍物阻止蚯蚓到达目标刺激物时，在远处观察到了吸引力，这证实了挥发性线索的作用。这些发现增进了我们对土壤生态系统中关键营养相互作用的机制的理解，并且对于在蚯蚓养殖和其他应用活动中提取和收集蚯蚓具有潜在的意义。
