The velvet crab (''Necora puber''), also known as the velvet swimming crab or devil crab, is a species of

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 ...

from the North-East Atlantic and the Mediterranean.

Classification

The velvet crab was first formally described in 1767 by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in the second part of the first volume of the twelfth edition of his definitive work ''

Systema Naturae ' (originally in Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the syste ...

.'' Linnaeus gave it the name ''Cancer puber;'' at the time, all crabs were classified indiscriminately into the genus ''

Cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

.'' ''Necora puber'' is commonly known as the "velvet crab", the "velvet swimming crab", and the "devil crab", the latter due to its aggressive behaviour and bright red eyes. In the Scottish fishing industry, they are sometimes known just as "velvets", and other less pervasive common names include the "velvet fiddler crab" the "lady crab", and the "Kerry witch". Linnaeus provided a very brief Latin description ‒ "vague and unsatisfactory", according to

Lipke Holthuis Lipke Bijdeley Holthuis (21 April 1921 – 7 March 2008) was a Dutch carcinologist, considered one of the "undisputed greats" of carcinology, and "the greatest carcinologist of our time". Holthuis was born in Probolinggo, East Java and obtained ...

. In fact, the identity of Linnaeus's crab in unclear, as no type material was assigned and the description given seems to more closely resemble ''Polybius corrugatus''. Since Linneaus' initial 1767 description, the velvet crab has been reclassified four times: first into '' Portunus'' by Fabricius in 1798, a classification which stood until 1958, when it was transferred to '' Macropipus'' by Holthuis and Gottlieb. In 1981 Manning and Holthuis moved it to '' Liocarcinus'', and six years later Holthuis reclassified the species into an entirely new genus, ''Necora'', of which the velvet crab is the only species. This classification still stands. The genus name ''Necora'' comes from the local word for the crabs in Galicia. Several species names described by other taxonomists have since been synonymised with ''Necora puber''.

Phylogenetics

Recent

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

studies of the

Portunoidea __NOTOC__ Portunoidea is a superfamily of crabs that includes the family Portunidae, the swimming crabs. Which other crab families are also placed here is a matter of some contention, and may be revised following molecular phylogenetic analyses ...

and related groups have considered ''Necora'' several times in their research. ''Necora'' is usually grouped with members of the genera '' Bathynectes'', '' Liocarcinus'', '' Macropipus'', ''

Polybius Polybius (; , ; ) was a Greek historian of the middle Hellenistic period. He is noted for his work , a universal history documenting the rise of Rome in the Mediterranean in the third and second centuries BC. It covered the period of 264–146 ...

'', and '' Thia''. A phylogenetic study published in '' Frontiers in Zoology'' in 2022 used both

maximum parsimony In phylogenetics and computational phylogenetics, maximum parsimony is an optimality criterion under which the phylogenetic tree that minimizes the total number of character-state changes (or minimizes the cost of differentially weighted charact ...

and

bayesian inference Bayesian inference ( or ) is a method of statistical inference in which Bayes' theorem is used to calculate a probability of a hypothesis, given prior evidence, and update it as more information becomes available. Fundamentally, Bayesian infer ...

and analysed morphological characteristics placed ''Necora puber'' in a monophyletic Carcinidae clade. Of the surveyed species, ''Necora'' was

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to a '' Macropipus rugosus'' / ''Thia'' grouping. However, a study using

nuclear DNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. ...

from 2009 placed ''Thia'' sister to a clade that includes ''Necora'', but also species from ''Macropipus'', ''Liocarcinus'', ''Polybius'', and ''Bathynectes''. The authors of the 2009 study noted that the conventional classifications of the

and Canceroidea have recently been challenged, and some morphological traits – especially those of 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 ...

and the

chelae A chela ()also called a claw, nipper, or pinceris a pincer-shaped organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through Neo-Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds ...

– can be affected by

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

. The 2016 study kept ''Necora'' in the Polybiidae. A yet earlier (2001) study using

mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

of 46 species paired ''Necora'' with '' Bathynectes maravigna'', close to ''Macropipus tuberculatus'' and ''Thia''.

Distribution

In the

British Isles The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebr ...

, velvet crabs are found from

Orkney Orkney (), also known as the Orkney Islands, is an archipelago off the north coast of mainland Scotland. The plural name the Orkneys is also sometimes used, but locals now consider it outdated. Part of the Northern Isles along with Shetland, ...

around Scotland, England, Wales, and Ireland. They also live in the nearby

German Bight The German Bight ( ; ; ); ; ; sometimes also the German Bay) is the southeastern bight of the North Sea bounded by the Netherlands and Germany to the south, and Denmark and Germany to the east (the Jutland peninsula). To the north and west i ...

and in parts of the West Frisian Islands.

Description

Velvet crabs have a dark, flattened

which ranges from black to brown in colour and is usually around 6.5 cm long and up to 10 cm across, weighing up to 250 grams. The carapace is

pubescent The adjective pubescent may describe: * people or animals undergoing puberty * plants that are hairy, covered in trichomes * insects that are covered in setae In biology, setae (; seta ; ) are any of a number of different bristle- or hair-lik ...

with short yellowish hairs providing a velvety texture. Tubercles are scattered across the upper surface, with a higher concentration towards the front. The frontal part of the crab's underside has some tubercles as well and is densely hairy. The front of the carapace is mostly straight and bends slightly inwards at the centre line; the front edge bears seven to ten tooth-like indentations. The

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthro ...

-bearing legs (the chelipeds) also have short hairs and are of equally short length. The "wrist" is armed with a spine on its outer side.

Conservation

Velvet crabs are "very common".

French fisheries

In France, velvet crabs are considered a delicacy. Fisheries in south

Brittany Brittany ( ) is a peninsula, historical country and cultural area in the north-west of modern France, covering the western part of what was known as Armorica in Roman Gaul. It became an Kingdom of Brittany, independent kingdom and then a Duch ...

, France's main producers of velvet crabs, suffered in the late 20th century due to mass mortality events; between 1984 and 1988 the catch dropped by 96%. The decline was attributed to infections by

dinoflagellates The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

which a 1996 investigation tentatively identified as belonging to the genus '' Hematodinium.'' Velvet crabs - geograph

British fisheries

Velvet crabs are traditionally eaten in France and Spain, and are commercially important for the

, although they were there once regarded as pests. In the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

, the velvet crab catch is regulated by ''The Undersized Velvet Crabs Order 1989,'' which enforced a

minimum landing size The minimum landing size (MLS) is the smallest fish measurement at which it is legal to keep or sell a fish. The MLS depends on the species of fish. Sizes also vary around the world, as they are legal definitions which are defined by the local regu ...

of 6.5 cm across the carapace, although it is also customary to throw back egg-bearing females when caught. Targeted fishing for the crabs is a recent phenomenon in Ireland, having started in the 1980s in response to increased demand due to the collapse of the Spanish velvet crab fisheries and thus of the southern European stocks. Velvet crabs are found all around Ireland, where the crabs are often taken as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

from edible crab and

lobster Lobsters are Malacostraca, malacostracans Decapoda, decapod crustaceans of the family (biology), family Nephropidae or its Synonym (taxonomy), synonym Homaridae. They have long bodies with muscular tails and live in crevices or burrows on th ...

fisheries, but they are fished for in the

Irish Sea The Irish Sea is a body of water that separates the islands of Ireland and Great Britain. It is linked to the Celtic Sea in the south by St George's Channel and to the Inner Seas off the West Coast of Scotland in the north by the North Ch ...

. Between 2006 and 2014, the volume of velvet crabs caught in Ireland decreased by nearly 100 tonnes, down from 230 tonnes, prompting concerns from fishermen and the

fishing industry The fishing industry includes any industry or activity that takes, cultures, processes, preserves, stores, transports, markets or sells fish or fish products. It is defined by the Food and Agriculture Organization as including recreational, sub ...

. In 2003, the velvet crab catch in Ireland was worth £5,812 a year. Velvet crab fisheries in Scotland have a similar history: the crabs were once regarded as pests, but the 1980s supply crisis prompted the emergence of a Scottish fishery. Today, Scotland is in fact Europe's largest fisher of velvet crabs, although the crabs are rarely targeted specifically and are caught alongside edible crabs and lobster. In 2011, the Scottish velvet crab fishery caught £5.8 million worth of crabs, or more than two thousand tonnes. The most productive areas are around the Scottish islands and west coast, the fishery having started around the

Hebrides The Hebrides ( ; , ; ) are the largest archipelago in the United Kingdom, off the west coast of the Scotland, Scottish mainland. The islands fall into two main groups, based on their proximity to the mainland: the Inner Hebrides, Inner and Ou ...

and

islands, but an east coast industry is also emerging. Although the industry is regulated, the crabs may be being overfished in the

Firth of Clyde The Firth of Clyde, is the estuary of the River Clyde, on the west coast of Scotland. The Firth has some of the deepest coastal waters of the British Isles. The Firth is sheltered from the Atlantic Ocean by the Kintyre, Kintyre Peninsula. The ...

, Orkney and South

Minch The Minch () is a strait in north-west Scotland that separates the mainland from Lewis and Harris in the Outer Hebrides. It was known as ("Scotland's firth") in Old Norse. The Minch's southern extension, which separates Skye from the middle ...

. In England, the velvet crab fishery reached its peak in 2006, and in 2011 around 200 tonnes of crabs worth £290,000 were landed. Velvet crabs are also found around the

Isle of Man The Isle of Man ( , also ), or Mann ( ), is a self-governing British Crown Dependency in the Irish Sea, between Great Britain and Ireland. As head of state, Charles III holds the title Lord of Mann and is represented by a Lieutenant Govern ...

, but it is not of primary interest to the fishing industry there.

Notes

Citations

Bibliography

*Adema, J.P.H.M., 1991. "De Krabben van Nederland en Belgie" (in Dutch), published by the Nationaal Natuurhistorisch Museum. *Barreto, Elisa and Bailey, Nick, 2013
"Fish and Shellfish Stocks, 2013 Edition"
published by the

Scottish Government The Scottish Government (, ) is the executive arm of the devolved government of Scotland. It was formed in 1999 as the Scottish Executive following the 1997 referendum on Scottish devolution, and is headquartered at St Andrew's House in ...

. ; *Collins, Evelyn ''et al.'', 2022. "High prevalence of ''Paramarteilia canceri'' infecting velvet swimming crabs ''Necora puber'' in Ireland", published in ''Diseases of Aquatic Organisms'' volume 148.
CC-BY 4.0
* Cuvier, Georges and Latreille, Pierre André, 1834. ''The Animal Kingdom'', vol. 3. *Hazerli, Dennis; Höpel, Christoph Gert; and Richter, Stefan, 2022. "New insights into the evolution of portunoid swimming crabs (Portunoidea, Heterotremata, Brachyura) and the brachyuran axial skeleton", published in '' Frontiers in Zoology'' volume 19, no. 1 by BMC.
CC-BY-SA 4.0
*Hearn, Alex R., 2004. "Reproductive biology of the velvet swimming crab, ''Necora puber'' (Brachyura: Portunidae), in the Orkney Islands, UK" published in ''Sarsia'' volume 89. *Hinchliff, Laura; Dick, Jaimie; Sigwart, Julia; and Gilmore, Lynn, 2015. ''The velvet swimming crab (Necora puber) fishery in Northern Ireland: a study of populations and welfare to enhance sustainability'', published by Queen’s University Belfast and Seafish. *Holthuis, Lipke B., 1987.
''Necora'', a new genus of European swimming crabs (Crustacea, Decapoda, Portunidae) and its type species, ''Cancer puber'' L., 1767
, published in '' Zoologische Mededelingen'' volume 61 no. 1 by the National Museum of Natural History, Leiden. *Ingle, Raymond W., 1980. ''British Crabs'', published by

Oxford University Press Oxford University Press (OUP) is the publishing house of the University of Oxford. It is the largest university press in the world. Its first book was printed in Oxford in 1478, with the Press officially granted the legal right to print books ...

. *Linnaeus, Carl, 1767. ''Systema Naturae'', 12th edition, vol. 1 part 2. *Schubart, Christoph D. and Reuschel, Silke, 2009.
A proposal for a new classification of Portunoidea and Cancroidea (Brachyura: Heterotremata) based on two independent molecular phylogenies
in ''Decapod Crustacean Phylogenetics'', 1st edition, published by

CRC Press The CRC Press, LLC is an American publishing group that specializes in producing technical books. Many of their books relate to engineering, science and mathematics. Their scope also includes books on business, forensics and information technol ...

. *Trewhella, Steve; and Hatcher, Julie, 2021.
The Essential Guide to Beachcombing and the Strandline
', published by

Princeton University Press Princeton University Press is an independent publisher with close connections to Princeton University. Its mission is to disseminate scholarship within academia and society at large. The press was founded by Whitney Darrow, with the financial ...

. {{Taxonbar, from=Q853487 Portunoidea Crabs of the Atlantic Ocean Crustaceans described in 1767 Taxa named by Carl Linnaeus