Abstract
Cuttlefish lack parental care, and hatchlings face high predatory risk immediately after hatching. Thus, cuttlefish hatchlings need to equip the anti-predatory ability as soon as they hatch. Pharaoh cuttlefish Sepia pharaonis and European common cuttlefish Sepia officinalis have similar morphological appearances, but their egg characteristics are distinctly different. Pharaoh cuttlefish produce eggs with transparent capsules, and European common cuttlefish produce eggs with a black envelop which is stained by ink. Previous studies have shown that sensory systems of European common cuttlefish are fully developed in late embryonic stages, and they can use these sensory systems to receive information from the environment. Moreover, European common cuttlefish can alter their food preference by their embryonic visual experience. However, there is little known about the effect of embryonic experience to predatory cues on postnatal behaviors in cuttlefish. Compared with European common cuttlefish, eggs of pharaoh cuttlefish are more vulnerable to predators, but the transparency of eggs may provide embryos an opportunity of collecting visual cues from the environment and thus increase their survival rate. The present study was aimed to understand whether cuttlefish’s embryonic experience of predators affects their postnatal defensive behaviors, and to compare the difference between pharaoh cuttlefish and European common cuttlefish. During the embryonic exposure period, all eggs of cuttlefish were separated into seven groups: one control group and six cue exposure groups. Embryos in three groups were exposed to the predatory cues (visual cue only, chemical cue only, and combination of visual and chemical cues). Similarly, Embryos in the other three groups were exposed to the cues of non-predator. Cuttlefish were tested their primary and secondary defensive behaviors after they hatched. The result showed that early exposure to predatory cues altered the cuttlefish hatching period and postnatal defensive behavior. However, effects of embryonic sensory information were different in pharaoh cuttlefish and European common cuttlefish. Specifically, visual information is more important than chemical information for pharaoh cuttlefish embryos, and chemical information may even reduce these effects. In contrast, visual information and chemical information are equally important for European common cuttlefish embryos. These results may explain the functional difference between egg appearance of two species.