''Portunus trituberculatus'', also known as the ''gazami'' crab, Asian blue crab or horse crab, is the most widely fished

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

in the world. It is found off the coasts of

East Asia East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of Economy of China, China, Economy of Ja ...

and is closely related to ''

Portunus armatus ''Portunus armatus'' (also known as ''Neptunus armatus'') is a species of crustacean, a swimming crab in the family Portunidae found in Australia and eastwards to New Caledonia. Common names include blue swimmer crabs, Blue manna, Blueys, and Jen ...

''.

Fishery

''Portunus trituberculatus'' is the world's most heavily fished crab species, with over 300,000

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...

s being caught annually, 98% of it off the coast of

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. This is because it is considered highly nutritious, especially in regard to crab cream (roe).

Distribution

''Portunus trituberculatus'' is found off the coasts of

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

, and

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

Description

The

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

may reach wide, and from front to back. ''P. trituberculatus'' may be distinguished from the closely related (and also widely fished) ''P. armatus'' by the number of broad teeth on the front of the carapace (three in ''P. trituberculatus'', four in ''P. armatus'') and on the inner margin of the merus (four in ''P. trituberculatus'', three in ''P. armatus'').

Relationship to humans

Controversy

Due to the increased farming scale and breeding of ''Portunus trituberculatus,'' the farming environment of the gazami crab has greatly decayed. It has also diminished the gazami crab's immune system which has led to the decline in its ability to fight off diseases. This can be observed by looking at the tooth-paste disease along with the emulsification disease that is caused by vibrio. These two diseases have caused a great deal of damage to ''Portunus trituberculatus'' which has created severe economic losses and deprivation to the industry. These diseases have ultimately reduced the comfort and healthy evolution of the gazami crab's farming industry.

Taxonomy

''Portunus trituberculatus'' was first described by

Edward J. Miers Edward John Miers FZS FLS (1851–15 October 1930) was a British zoologist and curator of the crustacean collection at the Natural History Museum in London. He contributed to the scientific reports from the ''Challenger'' expedition of 1872–1 ...

in 1876, under the name ''Neptunus trituberculatus''. To better understand the species development, evolution and reproduction a reference genome has been sequenced, assembling to 1.0 Gb in size and anchoring to 50 chromosomes. And demonstrating it diverged from the

Chinese mitten crab The Chinese mitten crab (''Eriocheir sinensis''; ; Jyutping: daai6 zaap6 haai5; Shanghainese: ''du6-zaq8-ha5'', "big sluice crab"), also known as the Shanghai hairy crab (, p ''Shànghǎi máoxiè''), is a medium-sized burrowing cr ...

around 183.5 million years ago.

Virus research

In 2019 it was discovered that gazami crab populations in China are commonly infected with the ''

Flavivirus ''Flavivirus'', renamed ''Orthoflavivirus'' in 2023, is a genus of positive-strand RNA viruses in the family ''Flaviviridae''. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika viru ...

'' Wenzhou shark flavivirus which was previously identified in all tissues of the Pacific spadenose shark, ''Scoliodon macrorhynchos''. While currently unknown if Wenzhou shark flavivirus causes disease in infected shark hosts, this virus moves horizontally between gazami crabs and sharks in ocean ecosystems in a manner similar to other Flavivirus infections such as

Dengue virus Dengue virus (DENV) is the cause of dengue fever. It is a mosquito-borne, single positive-stranded RNA virus of the family ''Flaviviridae''; genus '' Flavivirus''. Four serotypes of the virus have been found, and a reported fifth has yet to be ...

, which cycle horizontally between arthropod (mosquito) and vertebrate hosts.

References

{{Taxonbar, from=Q1186447 Portunoidea Edible crustaceans Commercial crustaceans Crustaceans described in 1876 Korean seafood Taxa named by Edward J. Miers