#pteropoda

Settle in with a Sea Angel

Better known as the naked sea butterfly or the common clione, Clione limacina is a species of pelagic sea slug (aka sea angels or gimnosomates) found throughout the open water of the north Atlantic, north Pacific and Arctic Oceans. They reside in both the epipelagic and mesopelagic regions, from the surface to depths of over 500 m (1,600 ft). As extremophiles, they can withstand extremely cold temperatures of −0.5 to 3°C (32°F to 37°F).

The common clione is named for its wing-like fins, which propel it through the water. The body is otherwise quite simple in design, and completely transluscent save for the organs, which are a vibrant orange. C. limacina is also notable for being the largest sea angel; the northernmost populations can reach 7–8.5 cm (2.8–3.3 in) in length.

Though they look beautiful the naked sea butterfly is actually a voracious predator. They primary prey are tiny, shelled sea butterflies. When it encounters a target, the sea angel's 'head' opens and it extracts the butterfly from its shell using a set of tentacles and chitinous hooks. When it cannot find sea butterflies, C. limacina will also consume small amphipods copepods. However, they can also survive up to a year without food of any kind. In turn, common cliones are also prey for a variety of marine life including fish such as chum salmon, and baleen whales.

Though little is known about the reproductive habits of C. limacina, research suggests that they are simultaneous hermaphrodites; individuals contain the sex organs for both males and females. They mating peaks during the spring and summer, and lay about 30-40 eggs afterwards. The larvae stay in the top 200 m (650 ft) of the water column to feed on phytoplankton until they reach maturity. It is generally thought that they can live to be about two years old in the wild.

Conservation status: Clione limacina has not been evaluated by the IUCN; however, like most sea slugs, they have a large population and are not considered to be endangered. However, they may be threatened by the rising temperatures in their natural habitat.

Photos

Kevin Raskoff

Richard Satterlie