Effects of embryonic exposure to predators on the postnatal defensive behaviors of cuttlefish
Résumé
Cuttlefish lack parental care and juveniles face a high predatory risk immediately after hatching. Previous studies have shown that the sensory systems of cuttlefish are functional before hatching, and embryos can recognize predatory visual and chemical cues innately. However, it is not known whether the embryonic experience of predatory cues impacts their postnatal defensive behaviors. Cuttlefish eggs (Sepia pharaonis with transparent capsule and Sepia officinalis with black capsule) were separated into seven groups: one control group and six cue-exposure groups. Embryos in the cue-exposure groups were exposed to either one of three types of predatory cues (visual, chemical, and both) or one of three similar types of non-predatory cues. Primary and secondary defensive behaviors of the cuttlefish hatchlings were examined at one week of age. The results showed that an early exposure to predatory cues in both species altered cuttlefish's hatching time and their postnatal primary defensive behaviors. However, embryonic sensory experience had different impacts on defensive behaviors in two species of cuttlefish. Specifically, visual information appeared to be more salient than olfactory information for S. pharaonis embryos, while both visual and olfactory cues seemed to influence S. officinalis embryos equally. These findings demonstrate that the embryonic sensory experiences of cuttlefish from these two species differentially affect the development of defensive behaviors among hatchlings.