First description of polyp bailout in cold-water octocorals under aquaria maintenance

Cnidarians, characterized by high levels of plasticity, exhibit remarkable mechanisms to withstand or escape unfavourable conditions including reverse development which describes processes of transformation of adult stages into early developmental stages with higher mobility. Polyp bailout is a stress-escape response common among scleractinian species, consisting of massive detachment of live polyps and subsequent death of the mother colony. Here, we describe two cases of polyp bailout in the cold-water octocoral species Acanthogorgia armata and Acanella arbuscula . During maintenance in aquaria, specimens of both species presented coenosarc withdrawal and loss of sclerites, followed by detachment of intact polyps. This is a strong indication of reverse development which can be a very important strategy under stress conditions and has not been reported before in cold-water octocorals.