Polyp bail-out in the scleractinian coral, Seriatopora hystrix, from the Great Barrier Reef

Colonies of the coral, Seriatopora hystrix, were collected monthly from Britomart Reef and Davies Reef between November 1979 and June 1981 for a study of seasonality in planulation.In the laboratory colonies were placed in non-aerated aquaria with non-circulating seawater to induce planulation. While monitoring the release of planulae, it was also observed that individual polyps were detaching themselves from the skeleton. Branches were collected and the detachment process was examined closely with a dissecting stereoscopic photo-microscope (Wild M-5A) and documented.Polyps were collected and transferred to plastic jars containing clean seawater, where individual polyps were monitored for up to 9 days to record the success of settlement and initiation of skeleton secretion. Polyps showing evidence of skeleton secretion were collected, tissue was removed from the skeletons and the skeleton examined using a scanning electron microscope. Field observations of polyp bail-out were also made at Britomart and Davies Reefs and were photographed using a Hasselblad 50 OEL/M camera in an underwater housing.
During a laboratory study of seasonality of planulation in the coral Seriatopora hystrix, it was observed that the environmental stress used to induce planulation, resulted in individual polyps detaching themselves from the coral skeleton. Further research was initiated to describe this escape response.