Common name: Sea angel, Naked sea butterfly, common Clione
Scientific name:Â Clione limacina
Author:Â Chloe Stone
Photos:  Special thanks to Alexander Semenov for allowing us to use his beautiful images of Clione limacina.Â
Size range:Â 3 cm to 8 cm
Identifying features:  Clione limacina are a type of pelagic sea slug. They have a unique pair of swimming wings called pteropodia which are wing-like extensions of their modified foot. The translucent body of these creatures show the pink or yellow couloured internal organs.Â
The sea butterfly Clione limacina. Three pairs of bucal cones can be seen at the mouth. These will expand into finger-like structures to grab hold of their prey when feeding.
Habitat:  Clione limacina inhabit the cold ocean waters of the Pacific, Arctic and sub-Arctic along with some C. limacina being found in the Sea of Okhotsk, Japan. They live anywhere from the surface of the water up to 600 meters deep.Â
Prey: The Sea Angel feeds almost exclusively on Limacina helicina, a sea butterfly (Pteropod) that has retained its shell. C. Limacina use their three pairs of buccal cones (finger-like tentacles) to drag the L. helicina towards their mouth where they use chitinous hooks to pull the prey out of its shell and use their rasping radula to eat. All of the feeding structures are normally hidden until they are feeding.
Predators: Sea Angels have a number of predators including Baleen whales, such as right whales, blue whales, and humpback whales, as well as fish such as the Chum salmon (Oncorhynchus keta). Baleen whales take in water that has lots of different types of microscopic species, usually including Clione limacina, and filter it through their baleen before swallowing.Â
Life cycle: The sea angel is a hermaphrodite able to produce both sperm and eggs.  Mating between the angels involves cross-fertilization and results in about 20-30 fertilized eggs. The eggs are laid in a gelatinous mass where they hatch into a larval form. The larval stage of Clione limacina is a shelled pteropod. The larva’s shell is thimble shaped and it’s mouth has a ciliated ring. Once they grow out of the larval stage, the Sea Angel loses its shell and ciliated band, grows wings and elongates its body. Clione limacina live up to two years.Â
References:
Brady, H. (2017, September 20). Rare Video Shows Sea Angels’ Graceful Mating Dance. Retrieved from https://www.nationalgeographic.com/news/2017/09/sea-angels-mating-arctic-video-spd/
Maoka, T., Kuwahara, T., & Narita, M. (2014, March 13). Carotenoids of sea angels Clione limacina and Paedoclione doliiformis from the perspective of the food chain. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3967221/
Pteropoda by Alexander Semenov. (n.d.). Retrieved from http://coldwater.science/project/pteropoda
Wrobel, D., & Mills, C. E. (2003). Pacific coast pelagic invertebrates: a guide to the common gelatinous animals. Monterey CA: Monterey Bay Aquarium.