Sea butterflies are part of the cladeThecosomata. Sea angels, similar to Limacina, are in the order Gymnosomata. Both of these orders are still referred to as "pteropods". Sea butterflies of the order Thecosomata have a shell, while sea angels in the order Gymnosomata do not.
The shells of Limacina are well developed, sinistrally coiled, turret-like, and include an operculum. Shell size and thickness vary within the genus. At high latitudes, the diameter of the shell does not exceed 15 mm. At lower latitudes, the diameter varies from 1 to 3 mm.
Two large winglike parapodia, derived from foot tissue, propel these invertebrates through the water column to overcome negative buoyancy due to the animal's shell. As diel vertical migrators, Limacina inhabit deeper waters during the day and travel to the surface at night to feed.
Feeding habits of Limacina are characterized by actively feeding on planktonic organisms such as bacteria, small crustaceans, gastropod larvae, dinoflagellates and diatoms. These prey items become entangled in a mucosal web (up to 5 cm wide) excreted by the animal that is, in turn, eaten along with the prey items. This net also provides positive buoyancy. Ciliated posterior footlobes and lateral footlobes move food collected by the mucosal web into the mouth.
Large aggregations of Limacina migrating to the surface of the water attract predators such as Clione (family Clionidae, suborder Gymnosomata), baleen whales, various species of salmonids, herring,[5] and seabirds.
(recent) Limacina inflata (d'Orbigny, 1836) - Planorbid pteropod. Distribution: circumglobal, Red Sea, Pacific. Length: 1 mm. Description: the shell is flatly twisted, resembling the shell of the cephalopod Nautilus. - synonym: Heliconoides inflata (d'Orbigny, 1836)
Limacina naticoides Souleyet, 1852: synonym of Limacina trochiformis (d'Orbigny, 1834)
Vaught, K.C. (1989). A classification of the living Mollusca. American Malacologists: Melbourne, FL (USA). ISBN0-915826-22-4. XII, 195 pp.
Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50: pp. 180–213
