Some species (excluding "Planctoteuthis") are bioluminescent, with photophores (light-producing organs) variably present on the inner surface of the ventral arms, on the ventral surface of the eyes (one to three patches or bands), on the ink sac, and near the club terminus. A number of chambers containing ammonium chloride are contained within the arms, head, and mantle. With a lower density than the surrounding seawater, the ammonium chloride helps chiroteuthids to conserve energy reserved for swimming by maintaining the body's neutral buoyancy. The eyelid sinus is indistinct, occpital folds are absent, and long stalks support the olfactory papillae. The largest species reach a mantle length of about 78 cm. Body coloration is typically beige to sepia, but "Asperoteuthis acanthoderma" is noted for its deep violet color.