The sea butterfly is a tiny sea snail that swims by flapping its enlarged foot like wings to elegantly soar through the open ocean.
And if that does not astonish enough, these small creatures have mastered a very unusual technique: They hunt by sneezing.

Limacina helicina   © Alexander Semenov

Thecosomata is the scientific name of these molluscs which are common all over the world’s oceans. This species is pelagic, which means it is distributed in the open ocean, away from the shore and close to the surface. They float with the currents or swim by flapping slowly with two wing-like lobes, or parapodia, which propel this little animal through the sea.
These lobes are an evolutionary modification of the gastropod foot, which helps navigate towards nutrient rich hunting grounds and supports the otherwise sinking body of the snail.

The sea butterfly eats by secreting a web of mucus that can be much larger as the animal itself. It floats through nutrient rich waters and traps phytoplankton and other small particles. The net is then periodically eaten to acquire the food stuck to it.

Most sea snails have a thin, transparent shell that measures only about 1cm across. However, a few species have replaced the calcified shells with cartilage and others may lack any rigid structure.

These creatures, which are about the size of a lentil, are eaten by various marine species, including a wide variety of fish that are, in turn, consumed by penguins and polar bears. They form the sole food source of their relatives, the Gymnosomata or Sea Angels. And they are also consumed by sea birds, whales, and commercially important fish, which they can feed entirely if consumed in large quantities.

The shelled sea butterfly (Limacina helicina) is a key organism in the polar sea, where it can account for 50% of total zooplankton abundance.
But this well-balanced food chain is threated by the increasing amount of CO2 in our planet’s atmosphere. The result of ocean acidification could one day push all shelled sea butterflies towards extinction, with drastic and unimaginable effects on the future of the marine eco system.


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