''Clione okhotensis'' is a species of

sea angel Sea angels (clade Gymnosomata) are a large group of small free-swimming sea slugs, not to be confused with Cnidarians (Jellyfish and other similar creatures), classified into six different families. They are pelagic opisthobranchs in the clade G ...

, a pelagic marine

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

(sea slug) in the family

Clionidae The Clionidae are a family of sea angels, which are a group of pelagic marine gastropods. They resemble angels, complete with flapping "wings", hence their common name. They are gelatinous, mostly transparent pteropods, and they only have sh ...

Distribution

The only known localities of ''Clione okhotensis'' are in the southern

Sea of Okhotsk The Sea of Okhotsk ( rus, Охо́тское мо́ре, Ohótskoye móre ; ja, オホーツク海, Ohōtsuku-kai) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands ...

and the

Kuril–Kamchatka Trench The Kuril–Kamchatka Trench or Kuril Trench (russian: Курило-Камчатский жёлоб, ''Kurilo-Kamchatskii Zhyolob'') is an oceanic trench in the northwest Pacific Ocean. It lies off the southeast coast of Kamchatka and parallels ...

area in the western

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

. It has been found at depths of 0.3 to 1.5 m 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.

Description

''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 Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared ...

, as adults retain many juvenile characteristics upon maturing. As a result, ''Clione okhotensis'' strongly resemble and were previously mistaken for juvenile ''C. limacina''. 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 The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...

with buccal cones and

chitinous Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chiti ...

hooks for predation. 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.

Ecology

''Clione okhotensis'' inhabits cold, shallow waters of the Sea of Okhotsk. It is a specialized predator of ''

Limacina helicina ''Limacina helicina'' is a species of small swimming planktonic sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies (Thecosomata). ''Limacina helicina'' is a keystone species of mesozooplankton in Ar ...

,'' a species of sea snail. Like ''C. limacina'', it utilizes

hooks to secure its prey and swallow it whole. Although its buccal cones are unused in predation, they are still visibly retracted and extended during attempt behavior. 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''. A known predator of ''Clione'' species is the

pink salmon Pink salmon or humpback salmon (''Oncorhynchus gorbuscha'') is a species of anadromous fish in the salmon family. It is the smallest and most abundant of the Pacific salmon. The scientific species name is based on the Russian common name for ...

. Though the direct effects of

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

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 Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...

due to its

aragonitic Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...

(calcium carbonate) shell.

References

{{Taxonbar, from=Q59577325 Wikipedia Student Program Clionidae