Limacina helicina is a species of small swimming predatory sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies (Thecosomata).
Limacina helicina is a keystone species of mesozooplankton in Arctic pelagic ecosystems.
The first written record of this species was by Friderich Martens from Spitsbergen in 1675. Limacina helicina was also observed during an 1773 expedition to the Arctic led by Constantine John Phipps on the ships HMS Racehorse and on HMS Carcass and the species was described one year later, in 1774.
Limacina helicina is the type species of the genus Limacina.
In contrast to the traditional view, it was shown in 2010 that the distribution of this species is not bipolar; Arctic and Antarctic individuals belong to two genetically distinct species: Limacina helicina in the Arctic, and Limacina antarctica in the Antarctic.Limacina helicina has been recognised as a species complex comprising two sub-species and at least five forms. In addition, the taxonomic category “forma” has been applied to designate at least three morphotypes of Limacina helicina helicina (acuta, helicina and pacifica) and two morphotypes of Limacina helicina antarctica (antarctica and rangi). It is also known as Limacina helicina rangii (d'Orbigny, 1835). These forms typically have different geographical ranges, but it remains unclear as to whether forms represent morphological responses to different environmental conditions or are indeed taxonomically distinct, and if the latter, their level of taxonomic separation.