Clione okhotensis

The only known localities of Clione okhotensis are in the southern Sea of Okhotsk[2] and the Kuril–Kamchatka Trench area[3] in the western Pacific Ocean. It has been found at depths of 0.3 to 1.5 m (1 ft 0 in to 4 ft 11 in) below the surface of the water. Its distribution overlaps with those of C. limacina and C. elegantissima, two separate species of the same genus found in the North Pacific.[3][4]

Clione okhotensis only reaches up to 0.8 cm (0.3 in) in body length, making the species substantially smaller than most other Clione species, such as C. limacina, which has a body length of up to 3 cm (1.2 in) in comparison. The species is considered paedomorphic, as adults retain many juvenile characteristics upon maturing.[2] As a result, Clione okhotensis strongly resemble and were previously mistaken for juvenile C. limacina.[3]

Like all Clione species, Clione okhotensis is characterized by a translucent body revealing a bright orange-red visceral mass that occupies much of the upper middle body. Its mouth is represented by a radula with buccal cones and chitinous hooks for predation.[5] Although most Clione species utilize buccal cones for predation, the buccal cones of Clione okhotensis are much smaller than those of other species and are not utilized in predatorial behavior.[2]

Clione okhotensis inhabits cold, shallow waters of the Sea of Okhotsk. It is a specialized predator of Limacina helicina, a species of sea snail.[2] Like C. limacina, it utilizes chitinous hooks to secure its prey and swallow it whole.[5] Although its buccal cones are unused in predation, they are still visibly retracted and extended during attempt behavior.[2] During searching behavior, it excretes a sticky fluid and swims with its body elongated and stretched out, characteristics of predatorial behavior that are uniquely not present in C. limacina.[2] A known predator of Clione species is the pink salmon.[6] Though the direct effects of global warming on Clione okhotensis have yet to be evaluated, its populations could be negatively impacted by a decline in the populations of its primary prey, Limacina helicina, which is extremely vulnerable to ocean acidification due to its aragonitic (calcium carbonate) shell.[6][7]