thecosomata

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)

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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”.

Classification

Animalia-Mollusca-Gastropoda-Heterobranchia-Euthyneura-Euopisthobranchia-Thecosomata-Limacinoidea-Limacinidae-Limacina-L. antarctica

Image: R. Giesecke

Sea angels are mollusks native to the Arctic Ocean whose scientific name Gymnosomata is Greek for “naked body” and whose appearance is both ghostly and beautiful (see video below). Sea angels are hermaphroditic and feed on another, possibly related, species of “winged” mollusk known as the sea butterfly (Thecosomata). Since they appear to flutter through the water on tiny translucent wings it’s easy to see how sea angels got their common name, although they also have pointy protrusions that resemble horns…

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