Testing developmental requirements to induce escape hatching of cisco (Coregonus artedi) embryos

Escape hatching responses are naturally occurring hatching events where exposure to specific environmental stimulus elicit hatching of fish embryos earlier than observed without an external stimulus. This response can be caused by a variety of environmental stimuli, including rapid increases in water temperature. We conducted this study to understand if a certain level of larval development was needed for escape hatching to occur in cisco (Coregonus artedi) embryos. We observed whether the absence/presence of hatching glands and a minimum larval size threshold were required to elicit a temperature induced escape hatching response. Chronic exposure to environmental stressors can reduce survivorship of a developing embryo. Earlier hatching can act as a behavioral adaptation for the embryo to avoid persistent exposure to an environmental stressor. This behavior can only occur if the embryo is developmentally prepared to hatch. The developmental requirements for embryos to hatch are less understood, especially for fish species that are not commonly studied model organisms including cisco (Coregonus artedi). We conducted this study to understand if a certain level of larval development was needed for escape hatching to occur in cisco embryos. Eyed-up cisco embryos were exposed to an increase in water temperature and recorded if the embryo hatched or not. Then, we compared the hatching success to the presence of hatching glands and measured the embryo's total length as two potential estimates of development that could influence if the embryo is capable of escape hatching.