Can embryonic skipper frogs (Euphlyctis cyanophlyctis) learn to recognise kairomones in the absence of a nervous system?

Abstract

In this study, we used larval Euphlyctis cyanophlyctis to determine the predator recognition mechanism. We conducted a series of experiments to determine if larval E. cyanophlyctis have the innate ability to recognise predatory odour (kairomones) as a threat or if they learn to do so during ontogeny. In the case of learning, we wanted to determine the developmental window during which learning is accomplished. Further, we tested the antipredator response of predator- naive as well as predator-experienced tadpoles to chemical cues of different origins in order to assess if they exhibit differential responses. Our results clearly indicate that predator-naı¨ve tadpoles of E. cyanophlyctis do not reduce their activity against predatory cues of dragonfly nymphs, suggesting that they lack the innate ability to recognise kairomones. However, they could learn to do so when trained to perceive kairomones simultaneously along with alarm cues. Surprisingly, larval E. cyanophlyctis could learn to recognise kairomones through association during embryonic stages even before the development of a nervous system. Although larval E. cyanophlyctis lack the innate ability to recognise kairomones, they were able to recognise conspecific alarm cues on the first encounter, indicating that they have the innate ability to recognise alarm cues as a potential threat.