The sea butterfly is a suborder of swimming sea snails and a gastropod mollusk of the class Gastropoda. The sea butterfly’s scientific name is Thecosomata or thecosomes. The sea butterfly is as Pteropod, and is included in the group Pteropoda. They incorporate many species of gastropods and play a fundamental role in the oceanic ecosystem. They supply many creatures with a source of food and have an impact on the carbon cycle of the earth’s oceans.


The sea butterfly has developed parapodia, or lobes, that act as tiny wings. These winglike arms enable them to travel through the water and follow the currents. The sea butterfly is one of the tiny marine snails, rarely being seen larger than 1 cm. Sea butterflies are similar to sea angels. However, the latter does not have the calcified transparent shell. This calcium carbonate shell body allows them to adapt to the ocean’s acidity.

Sea Butterfly
Sea butterflies are known for their wing-like lobes


It is believed that sea butterflies are mostly passive feeders and use plankton as their food source. However, the methodology is very atypical. They use a 5 cm mucous web like a net to catch the planktonic food. This net is actually far bigger than the body of the sea butterfly. If their feed is disturbed, they will give up and throw the net away.

The sea butterfly follows a daily feeding pattern. They will migrate into the water column, following the plankton. They will then stay at the ocean surface, in the warm surface water at night, and then visit deeper waters at the start of the day.


The sea butterfly is a pelagic animal, meaning it occupies the most open of waters, rarely coming near the shore or the seafloor, and is found exclusively in seawater. They are known to occupy waters off the western coast of America, ranging from British Columbia to California. The North Atlantic Ocean is inhabited by them as well. They also range from the warm water of the tropics to the cold waters of the north and south pole.

The sea butterfly can appear in many different forms
The sea butterfly can appear in many different forms


Every sea butterfly possesses both male and female reproductive organs, making them hermaphrodites. However, until the butterfly grows, it starts as a male. It is only later on that they start to produce eggs, which are released into the water until they hatch.


One of the largest threats to the sea butterfly is the changes in its habitat. Due to the aragonitic shell of the creature, they are highly susceptible to the PH, or acidity of the water. As we know, humans are releasing more and more carbon dioxide and other harmful gasses into the air. This forces the ocean to absorb more CO2, which can cause ocean acidification or a change in the acidity of the ecosystem.

Sea butterflies have to contend with the threat of predators. Their extremely small size makes them an easy target and, more often than not, helpless prey. Whales and fish consume them, and other similar marine creatures, en masse, putting them in harm’s way. They also have to watch out for sea birds when they operate on the water’s surface.

Facts about the Sea Butterfly

  • Sea butterflies are hermaphroditic.
  • They are found all over the world in the open ocean.
  • They are called the ‘sea butterfly’ due to the wing-like lobes that they use to travel through the water.


Is a sea butterfly rare?

Sea butterflies are far from rare as they are abundant in the oceans, making them vital to the food chain.

Where does the sea butterfly live?

Sea butterflies are found all around the world in pelagic zones or deeper, open waters away from shorelines. They can be seen from the Arctic oceans to tropical oceans, inhabiting both cold and warm waters.

How do sea butterflies move?

Some sea butterflies have seen adaptations of their gastropodal foot, turning it into two lobes that resemble wings. These are called parapodia, which enables them to catch the water currents and move through the water.

About Ocean Info

At Ocean Info, we dive deep into ocean-related topics such as sealife, exploration of the sea, rivers, areas of geographical importance, sailing, and more.

We achieve this by having the best team create content - this ranges from marine experts, trained scuba divers, marine-related enthusiasts, and more.

Sea Anemone with Clownfish

Dive into more, the ocean is more than just a surface view

Shrimp vs prawn: Main differences

Shrimp vs Prawn

While these two animals look similar, there are notable main differences between shrimp and prawns, from their appearance and taste to their habitat. Read on to learn more.

Share to...