North Sea Shrimp ( Crangon crangon )
|Fabricius , 1798|
Crangon species are relatively delicate decapods with a shrimp-like habit, they reach about 5 centimeters in length and are sandy-brown to whitish-translucent in color. The elongated second antennae are almost body length. On the carapace , the rostrum, a protrusion reaching forward between the stalked complex eyes, is reduced to a small tooth. The carapace also has a central (median) and a lateral thorn or thorn. The first pair of striding legs (peraeopods) carries large scissors ( chela ), these are designed as subchela, that is, the end member can be folded in like a pocket knife against the massive base member. The slender and long second pair carries tiny scissors that serve as a cleaning organ. The remaining peraeopods are leg-like, with the third and fourth pair being the longest.
In order to differentiate the genus from related and similar forms, the following features are also essential: The peraeopods of the split bone do not have an outer branch (exopodites). The carpus (a leg segment) of the second pair of peraeopods is not divided into parts, the merus (a leg segment) of the first pair of peraeopods has a thorn on the underside (ventral). The dactylus (a leg link) of the fourth and fifth pair of peraeopods is not widened and flattened to improve swimming ability. On the third maxillipede (a pair of trunk legs that are transformed and specialized in the service of eating) there is an arthrobranch gill (that is, the gill sits in the joint membrane between the basic phalanx, the coxa, and the body wall).
The Crangon species are found in the marine waters of the northern hemisphere. Three species live in the Atlantic, two of them in the northeast and one in the northwest Atlantic. Fifteen species are known from the North Pacific, seven species each on the Asian and American coasts, only one species ( Crangon dalli ) on both. The Atlantic species are the North Sea shrimp and Crangon allmanni in the eastern Atlantic, off the Eurasian coast, and Crangon septemspinosa in the western Atlantic, off the American coast. With the exception of the North Sea shrimp, which is interesting for the fishing industry, many species have been poorly researched. Due to the high number of species, the genus probably originated in the Pacific. The Atlantic and the Pacific species have not yet been precisely delimited from one another, also on the basis of type material; according to the descriptions, they sometimes form very similar pairs of species, which could possibly be subspecies of a common species. According to genetic data, the species investigated in the Atlantic and Pacific, Crangon septemspinosa and Crangon alaskensis , separated from one another about 6.6 million years ago using the methods of the molecular clock .
Ecology and way of life
Crangon species live on the sea bed ( benthic ), mostly in the bank zone and the waters close to the shore (littoral and sublittoral), but some species up to a depth of a few hundred meters, always on soft substrates such as sand or mud bottom, rarely on gravel. Several generations per year of the species investigated in more detail have been identified or identified using abundance maxima. Some species are protandric hermaphrodites, with them young sexually mature animals are male, older and larger then transform into females. Since only the females can be identified with certainty (by means of the attached ice bags), the situation in most species is unclear. The species that live in shallow water, including the North Sea shrimp, often prefer to deposit the young in the brackish water of the estuaries.
Some species, such as Crangon crangon and Crangon septemspinosa , are sometimes found in their habitats in high density and in high numbers of individuals and are sometimes considered to be key ecological species . On the one hand, they are an important prey for fish and other marine life, but they can also limit the fish population themselves, as predators of fish larvae. With the exception of the well-studied North Sea populations of the North Sea shrimp Crangon crangon, there are hardly any studies on the population dynamics of the species.
The genus Crangon includes the following recent species:
- Crangon affinis De Haan , 1849 . In the North Pacific on the Asian Pacific coast from the Yellow Sea to Japan.
- Crangon alaskensis Lockington , 1877 . On the American Pacific coast from the Bering Sea south to Washington.
- Crangon alba Holmes , 1900 . On the American Pacific coast from Vancouver Island to California.
- Crangon allmanni Kinahan , 1860 . On the Eurasian Atlantic coast from the White Sea to the Biscay, and off Iceland, in greater water depths.
- Crangon amurensis Bražnikov , 1907 . On the Asian Pacific coast, Sea of Okhotsk to Japan.
- Crangon capensis Stimpson , 1860 . dubious species, never found again after the first description, given by the Cape of Good Hope .
- Crangon cassiope De Man , 1906 . In the North Pacific on the Asian Pacific coast from the Yellow Sea to Japan.
- Crangon crangon ( Linnaeus , 1758) . On the Eurasian Atlantic coast with secondary seas (North and Baltic Seas, Mediterranean, Black Sea), south to Morocco, in shallow water.
- Crangon dalli Rathbun , 1902 . Coasts of the North Pacific from Puget Sound over the Chukchi Sea to Japan.
- Crangon franciscorum Stimpson , 1856 . On the American Pacific coast from Alaska to California.
- Crangon hakodatei Rathbun , 1902 . On the Asian Pacific coast, Sea of Okhotsk to the Yellow Sea and southern Japan.
- Crangon handi Kuris & Carlton , 1977 . On the American Pacific coast to Northern California.
- Crangon holmesi Rathbun , 1902 . In the Pacific, off the coast of California.
- Crangon lockingtonii Holmes , 1904 . dubious nature, never found again after the first description. indicated by the Bahía Magdalena , Baja California.
- Crangon nigricauda Stimpson , 1856 . On the American Pacific coast, from Alaska to Baja California .
- Crangon nigromaculata Lockington , 1877 . On the American Pacific coast, from the Gulf of the Farallones in northern California to Baja California.
- Crangon propinquus Stimpson , 1860 . On the Asian Pacific coast, Sea of Okhotsk to northern Japan.
- Crangon septemspinosa Say , 1818 . Along the American Atlantic coast from the Gulf of St. Lawrence to Florida.
- Crangon uritai Hayashi & JN Kim , 1999 . In the North Pacific on the Asian Pacific coast from the Yellow Sea to Japan, also introduced as a neozoon in Port Phillip Bay , Australia.
Furthermore, two fossil species are known.
The generic name Crangon was controversial in its use for a long time. For the name Crangon Fabricius, 1798, which had been in use for a long time, later authors rediscovered an older homonym Crangon Weber, 1795, so that, in their opinion, another genus (today the genus Alpheus Fabricius, 1788) should bear this name. The dispute was only resolved by a formal resolution of the International Commission on Zoological Nomenclature , which laid down the use of the generic name in the current sense. A synonym for the generic name is Crago Latreille. The division of the genus into sub-genera proposed by the Russian researcher NA Zarenkov is hardly used today.
- Mary K. Wicksten: decapod crustacean of the Californian and Oregonian Zoogeographic Provinces. Magnolia Press, 2012. ISBN 978-1-86977-936-8 download from escholarship.org
- Ken-Ichi Hayashi, Jung Nyun Kim (1999): Revision of the East Asian species of Crangon (Decapoda: Caridea: Crangonidae). Crustacean Research 28: 62-103. download at Crustacean Research
- LB Holthuis: The recent genera of the Caridean and Stenopodidean shrimps (Class Crustacea, Order Decapoda, Supersection Natantia) with keys for their determination. Zoologische Verhandelingen 26. Brill Scientific Publishers, 1955. 153 pages.
- Joana Campos, Cláudia Moreira, Fabiana Freitas & Henk W. van der Veer: Short Review of the Eco-geography of Crangon. In: Journal of Crustacean Biology. 32, 2012, pp. 159-169, doi: 10.1163 / 193724011X615569 .
- S. De Grave & CHJM Fransen: Carideorum Catalogus: the Recent species of the dendrobranchiate, stenopodidean, procarididean and caridean shrimps (Crustacea: Decapoda) Archived from the original on December 20, 2012. Info: The archive link was automatically inserted and not yet checked . Please check the original and archive link according to the instructions and then remove this notice. In: Zoologische Mededelingen . 85, No. 9, 2011, pp. 195-589, figs. 1-59. ISBN 978-90-6519-200-4 .
- C. Fransen, S. De Grave, M. Türkay (2011): Crangon. World Register of Marine Species , accessed November 10, 2017.
- Joanne Taylor & Tomoyuki Komai (2011): First record of the introduced sand shrimp species Crangon uritai (Decapoda: Caridea: Crangonidae) from Newport, Port Phillip Bay, Victoria, Australia. Marine Biodiversity Records 4; e22; 6 pages. doi: 10.1017 / S1755267211000248
- Sammy De Grave, N. Dean Pentcheff, Shane T. Ahyong et al .: A classification of living and fossil genera of decapod crustaceans . In: Raffles Bulletin of Zoology . Suppl. 21, 2009, pp. 1-109.
- NA Zarenkov (1965): Reviziya Rodov Crangon fabricius i Sclerocrangon GO SARS (decapods, Crustacea). Zoologicheskii Zhurnal 44 (12): 1761-1775., English: Revision of the genera Crangon Fabricius and Sclerocrangon GO Sars (Decapoda, Crustacea). translated for the Fisheries Research Board of Canada Biological Station Nanaimo, BC, 1970.