Sea Angels and Sea Butterflies: The Horrible Truth…

Russian photographer Alexander Semenov captured these beautifully delicate sea creatures known as Sea Angels and Sea Butterflies. By capturing these little beauties on a black background, their transparent bodies seem to glow with a soft orange color.

Sea Angels (Gymnosomata) and Sea Butterflies (Thecosomata) are both included in the pteropod family, although some marine biologists argue against this. This is where any similarities end.

Sea angels are a form of sea slug while sea butterflies are a form of sea snail. Sea butterflies have broader bodies and a shell, which some of them retain. But there is a hidden, shocking truth about these lovely luminescent creatures of the sea…and, oh, the horror!

The sea angels eat the sea butterflies. 

The angels have terminal mouths common to mollusks, and tentacles to grasp their prey, sometimes with suckers similar to cephalopods. Their “wings” allow sea angels to swim much faster than the larger (usually fused) wings of sea butterflies. Nature can be cruel, but an angel has got to eat!

sources 1, 2, 3


It’s been a while since we last checked in with the Department of Awesome Natural Wonders. These beautiful creatures are called Sea Butterflies, which are small pelagic swimming sea snails. These particular Sea Butterflies were photographed by Russian biologist and photographer Alexander Semenov (previously featured here).

Sea Butterflies float and swim freely in the water, and are carried along with the currents. This has led to a number of adaptations in their bodies. The shell and the gill have disappeared in several families. Their foot has taken the form of two wing-like lobes, or parapodia, which propel this little animal through the sea by slow flapping movements. They are rather difficult to observe, since the shell (when present) is mostly colorless, very fragile and usually less than 1 cm in length.

Visit Alexander Semenov’s website and Flickr page to view more of his captivating photographs of fascinating marine life.

[via Design Taxi]


Clio recurva

sometimes known as the “Wavy Clio” C. recurva is a species of small cliid gastropod (a family of sea butterflies) that occurs in oceans worldwide. Like other cliid gastropods C. recurva is pelagic and characterized by a curved shell. Like most sea butterflies C. recurva possesses two paropodia which allow it to swim, they are also laced with cilia which produce a current that pushes planktonic food to its mouth.


Animalia-Mollusca-Gastropoda-Heterobranchia-Opisthobranchia-Thecosomata-Euthecosomata-Cavolinioidea-Cliidae-Clio-C. recurva

Images: Stephanie Bush and Karen Osborn

Sea Butterfly - Corolla spectabilis

Commonly referred to as Sea butterfly and also as Spectacular Corolla, Corolla spectabilis (Gastropoda - Thecosomata - Cymbuliidae) is a species of planktonic sea slugs, belonging to a group which are collectively called pteropods.

Corolla is characterized by having a single wing plate (those structures resembling wings), and a gelatinous internal pseudoconch which contains the visceral mass. The pseudoconch can grow to about 8cm in length in large animals, with a wing plate span of 16cm.   

One of the most interesting features of these sea butterflies is their method of feeding. They produce a mucous web, many times the size of the animal and can have a diameter of about 2m, to entangle and trap planktonic food. 

Reference: [1]

Photo credit: ©Arne Kuilman | Locality: Philippines (2013)

Limacina antarctica

…is a species of sea butterfly (a group of swimming sea snails that belong to the clade Thecosomata) that boasts a circumpolar distribution, occurring in the Weddell Sea and Ross Sea in the Antarctic and in Cumberland Bay, South Georgia and other areas in the southern ocean.  L. antarctica is most abundant in the Ross Sea and can sometimes even outnumber krill. L. antarctica is a predator and feeds mainly on phyto and zoo plankton, which are caught using “mucus webs”.


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Image: R. Giesecke


Cavolinia tridentata

…is a species of sea butterfly (Thecosomata) that has a wide distribution, occurring in European waters, the Mediterranean Sea, the Atlantic Ocean, the Northwest Atlantic, the Caribbean Sea, the Gulf of Mexico, the Indian Ocean and the Indo-Pacific. Like other sea butterflies C. tirdentata has two paropodia that allow it to “fly” through the water, they are also lined with cilia which produce a current which carries organic particles into its mouth.


Animalia-Mollusca-Gastropoda-Heterobranchia-Euthyneura-Euopisthobranchia-Thecosomata-Cavolinioidea-Cavoliniidae-Cavolinia-C. tridentata

Images: Ronald W. Gilmer and David Fenwick