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Papulae (sing. papula; also occasionally papulla, papullae), also known as dermal branchiae or skin gills, are projections of the coelom of Asteroidea that serve in respiration and waste removal [1] . Papulae are soft, covered externally with the epidermis, and lined internally with peritoneum. They extend through the mesodermal ossicles and are protected from microscopic larvae by pedicellariae. In a living specimen, the dermal gills can be extended or withdrawn.
