''Apostichopus japonicus'' is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
sea cucumber
Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...
in the family
Stichopodidae
The Stichopodidae are a family of sea cucumbers, part of the order Synallactida.
Description
Members of this family are mostly large or medium-sized holothuroids with a squarish cross-section, a flat ventral surface, and large, fleshy, cone-s ...
.
It is found in shallow temperate waters along the coasts of south east Asia and is commonly known as the Japanese spiky sea cucumber or the Japanese sea cucumber.
Description
The Japanese sea cucumber has a cylindrical leathery body with blunt, thorny protuberances. At the anterior or front end there is a mouth surrounded by a ring of short feeding tentacles and at the posterior end is the anus. There are three different colour
morphs, red, green and black.
[
]
Distribution and habitat
The Japanese sea cucumber is found along the coast of Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
, China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
and Korea
Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...
. The range extends from Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
and Sakhalin Island
Sakhalin ( rus, Сахали́н, r=Sakhalín, p=səxɐˈlʲin; ja, 樺太 ''Karafuto''; zh, c=, p=Kùyèdǎo, s=库页岛, t=庫頁島; Manchu: ᠰᠠᡥᠠᠯᡳᠶᠠᠨ, ''Sahaliyan''; Orok: Бугата на̄, ''Bugata nā''; Nivkh: ...
to the Amami Islands
The The name ''Amami-guntō'' was standardized on February 15, 2010. Prior to that, another name, ''Amami shotō'' (奄美諸島), was also used. is an archipelago in the Satsunan Islands, which is part of the Ryukyu Islands, and is southwest o ...
, Japan. The red morphs are found on gravel beds offshore at depths of or deeper while the other two colours are found intermingled on muddy and sandy bottoms at shallower depths.[ Although the red morph may breed red offspring due to its reproductive isolation in a different microhabitat, DNA studies have shown that there is a limited degree of genetic difference between it and the other two colour morphs while there is no significant difference between the black and green forms. In lagoons in southern Sakhalin, Russia, Japanese spiky sea cucumber are found on solid substrates among growth of the red alga '''' and in oyster beds ('']Crassostrea gigas
The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand.
Etymology
The genus ''Maga ...
'').
Biology
The Japanese sea cucumber sifts through the sediment on the seabed with its tentacles and feeds on detritus
In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...
and other organic matter including plant and animal remains, bacteria, protozoa
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
, diatoms
A diatom (New Latin, Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group com ...
and faeces.[
The sexes are separate in the Japanese sea cucumber. Males and females release a mass of gametes into the sea where fertilization takes place. In the laboratory, spawning from ripe gonads can be induced by varying the temperature at which the adults are kept or by use of the neuropeptide ''cubifrin''. The ]plankton
Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...
ic larvae develop through several stages before settling on hard surfaces on the seabed, undergoing metamorphosis and becoming juveniles.
The Japanese sea cucumber lives in temperate seas. In locations where the water heats up excessively in summer it undergoes aestivation
Aestivation ( la, aestas (summer); also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and ...
, going into a state of dormancy.[ In this state, feeding stops, the gut degenerates, the metabolism slows down and weight is lost. The threshold temperature is about , higher for smaller individuals and for those from the southern part of the range where the ambient water temperature is higher.] This sea cucumber has been known to continue in aestivation in some areas of China for four years.
Use as food
The Japanese sea cucumber is used as food. The largest fishery is in Japan where between 2000 and 2005, an average of 8,101 tonnes of this species were harvested annually.[ The red form is known there as "aka namako" and sells at a different price from "ao namako", the green morph and "kuro namako", the black one. In Russia and North Korea, overfishing has reduced populations considerably.][ Fishing methods include diving and hand collection at depths of up to and the use of trawls at greater depths. In the 1920s, a "sea cucumber fork" was developed in China. It is operated from several small vessels working together and allows harvest from depths of up to .][
The Japanese sea cucumber is also cultivated on a commercial scale in shallow ponds and by sea ranching in northern China, where production reached 5,865 tonnes in 2002.][ Rocks and tiles are placed on the bottom to provide settlement for larvae and protection from predators.][ Breeding programs are under way to improve growth rates and disease resistance and the genome is being sequenced.][ Hatchery techniques are being developed in Japan and China as are the preparation of suitable culture feeds and the investigation of the best methods of ranching.][ Albino forms and a thermally resistant strain that is less prone to aestivate are being developed in China.]
References
{{Taxonbar, from=Q2198517
Stichopodidae
Animals described in 1867
Fauna of the Pacific Ocean
Sea cucumbers as food