Ribonucleotides (inosine 5ʹ-monophosphate, guanosine 5ʹ-monophosphate, and adenosine 5ʹ-monophosphate) and histidine induce swimming activity in a predaceous diving beetle (Cybister brevis)

A device (with installed phototransistors as sensors) was used to quantitatively measure the behavior of a predatory diving beetle (Cybister brevis Aubé, 1838) and to record behavioral data every 0.2 sec for 10 min. The insect was provided with ribonucleotides (inosine 5ʹ-monophosphate, guanosine 5ʹ-monophosphate, adenosine 5ʹ-monophosphate), and amino acids (glutamate, taurine, histidine), abundant in the insect’s diet. These ribonucleotides and histidine induce swimming activity in insects. No effect of glutamate or taurine on behavior was observed at 250 mg. The effect of a mixture of these four chemicals was much greater than that of each chemical alone (synergistic effect). The dose-dependency of each chemical and the mixture was observed. Two traps were set in an aquarium, one contained an agar block with the mixture, and the other contained an agar block without any chemicals. All beetles were caught in the trap with the mixture. These results suggest that predaceous diving beetles use the smell of these ubiquitous organic molecules to locate food and induce food-searching activities. This study highlights our poor understanding of the feeding attractants of Dytiscidae insects and will pave the way for investigating prey-predator interactions at the material and molecular levels in this species.