The horsehair crab, ''Erimacrus isenbeckii'' (Japanese: ケガニ, ''kegani''), is a species of

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

which is found mainly in the Northwest

Pacific 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 ...

, around the

Hokkaido is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel. The la ...

coast in the

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 Western

Bering Sea The Bering Sea (, ; rus, Бе́рингово мо́ре, r=Béringovo móre) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasses on Earth: Eurasia and The Ameri ...

and is an important commercial species used in

Japanese cuisine Japanese cuisine encompasses the regional and traditional foods of Japan, which have developed through centuries of political, economic, and social changes. The traditional cuisine of Japan (Japanese: ) is based on rice with miso soup and other ...

. Despite the importance of the species, biological studies are usually specialized and limited. The catch for the species reached a peak in the 1950s at 27,000 tons and has decreased since, reaching 2,000 tons in 2003. Due to the commercial importance of the species, many stock enhancement programs have been utilized to help maintain a successful fishery. The species is commonly found on sandy

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

environments from shallow water to depths of up to 350 meters.

Biology and description

''E. isenbeckii'' has a hard shell and soft spines which cover the shell and appendages. It can reach over 1 kg in weight. ''Erimacrus isenbeckii'' is known to feed three to four times in a ten to twelve hour time-span and

cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...

is common for ''E. isenbeckii'' in the spring. The

carapace A carapace is a Dorsum (biology), 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 tor ...

of ''E. isenbeckii'' can reach 100 to 120 mm in length in adults. Like the two other species in the same family, the gonophores of females are exposed. In the western Bering Sea, males typically live in areas of around 3.4 °C and depths of around 66 meters, while females can be found in temperatures of 2.4 °C and depths of around 64 meters.

Life cycle

The embryonic development of the species can be divided into 9 stages, each defined by cleavage and formation of distinct appendages. To incubate the eggs after spawning, females attach them to their

pleopods The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in variou ...

. Based on many surveys conducted during the spawning and hatching seasons, the incubation period of the species is estimated to be over a year, with the embryonic growth rate mainly being controlled by the temperature of the water. Young hatch between March to May and remain as

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

until they reach the bottom of the sea by July. The hatching process occurs during the spring

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

bloom in the Sea of Okhotsk. The

zoea Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

of this species can be mistaken for the two other species in the same family, but ''E. isenbeckii'' zoea lack carapace spines and have shorter lateral spines on the fork of the telson.

References

{{Taxonbar, from=Q797918 Crabs Crustaceans of the Pacific Ocean Crustaceans of Japan Commercial crustaceans Crustaceans described in 1848 Taxa named by Johann Friedrich von Brandt