Electroreception by small-spotted catshark (Scyliorhinus canicula) embryos in relation to predator detection and avoidance

Electroreception is an intriguing sense in the animal kingdom, that confers an advantage, when other senses cannot be used. Many shark and ray species spend a prolonged embryonic life stage enclosed in an egg case, where the avoidance of predators is difficult. In this study, we found that late stages of small-spotted catshark (Scyliorhinus canicula) exhibit a freeze response that stops ventilation when exposed to electric stimuli. The embryos also showed a short-term tolerance buildup, when exposed to several electrical stimuli over a 40-min period. Surprisingly, The embryos also reacted with a freeze response when the electrical field was turned off, indicating that the embryos reacted to a change in electrical field, rather than the presence of one. Younger embryos showed a significantly longer freeze response than older embryos. This study documents the use of electroreception in small-spotted catshark embryos as a possible predator avoidance response.