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Also, comb jellies are difficult to study because many of them live in deep water and are very fragile. The comb jellies that live in deep water have specializations in the membranes of their cells called plasmalogen lipids. These allow the cells to remain flexible even under extreme pressures. When these species are brought into shallower water their cell membranes tear apart because there is nothing holding them together.
There are new species of comb jellies being discovered as more of the deep ocean is explored. This species, Duobrachium sparksae, was just discovered in 2015.