BayCEER Workshop 2025

Submersed Electroantennography for Decoding Kairomone Perception in Daphnia: Linking Neural Responses to Ecologically Relevant Chemical Cues

Daphnia, a keystone genus in lentic ecosystems, can detect predator-released kairomones and respond with morphological, behavioural, or life cycle adaptations to reduce predation risk. Chemoreception in Daphnia is hypothesized to occur in the first antennae, however the chemosensory mechanisms underlying Daphnia’s responses to kairomones and the molecular identity of most kairomones remain poorly understood. Until recently a method for directly assessing their chemical perception was still lacking. A promising tool for measuring chemoperception in Daphnia is electroantennography (EAG) of the first antennae. EAG allows for direct measurement of electrical responses from chemosensory neurons upon exposure to chemical stimuli, providing a fast and sensitive method to screen potential kairomones and other ecologically relevant compounds. We established EAG for Daphnia magna and Daphnia longicephala. A positive control (algal volatile) with a simultaneously non-triggering negative control were implemented allowing for further testing of kairomones. Significant electrophysiological responses to roach (Rutilus rutilus) kairomones were then observed in D. magna. The testing of HPLC fractions of the roach extract allows us to find the physiologically active component in the roach kairomone. Having EAG as a new method to investigate chemoperception in Daphnia allows for a direct testing of various substances speeding up the process of unravelling the molecular structure of kairomones.