''Goneplax rhomboides'' 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 ...

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 ...

. It is known by the

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

angular crab because of its angular

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 ...

. Although it is also called the ''square crab'', its shell is in fact more

trapezoidal A quadrilateral with at least one pair of parallel sides is called a trapezoid () in American and Canadian English. In British and other forms of English, it is called a trapezium (). A trapezoid is necessarily a convex quadrilateral in Eucli ...

than

square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90-degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length adj ...

(or

rhomboidal Traditionally, in two-dimensional geometry, a rhomboid is a parallelogram in which adjacent sides are of unequal lengths and angles are non-right angled. A parallelogram with sides of equal length (equilateral) is a rhombus but not a rhomboid. ...

, as its

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

might suggest). This species is also known as the '' mud-runner'' because they are able to run away quickly when threatened.

Description

''Goneplax rhomboides'' is a relatively small (carapace up to in diameter), distinctive-looking crab that ranges from yellowish-white, to orange, too reddish to vivid pink in colour. It has a smooth, quadrangular, strongly convex carapace that is much broader than it is long. It has long, slender

pereiopod 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 various g ...

s with margins of propodus and dactylus

bristles A bristle is a stiff hair or feather (natural or artificial), either on an animal, such as a pig, a plant, or on a tool such as a brush or broom. Synthetic types Synthetic materials such as nylon are also used to make bristles in items such as br ...

. It likewise has

seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. Th ...

e on its antennae and mouthparts. Females have short

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

s but the chelipeds of males are long, with the merus portion of the claw considerably longer than the length of their carapaces. ''G. rhomboides'' has often been confused with '' G. clevai'', a similar species sharing at least part of its range. Its eyes are on the end of long, retractable eyestalks.

Distribution and habitat

''G. rhomboides'' is found in the northeastern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

and the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

from the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

to southern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

coast of

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

. Waters off

Shetland Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...

constitute the northern boundary of its range, and in 2008,

marine biologists Marine biology is the scientific study of the biology of marine life, organisms in the sea. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifie ...

from the

University of Gothenburg The University of Gothenburg ( sv, Göteborgs universitet) is a university in Sweden's second largest city, Gothenburg. Founded in 1891, the university is the third-oldest of the current Swedish universities and with 37,000 students and 6000 st ...

discovered one intact in the stomach of a

cod Cod is the common name for the demersal fish genus '' Gadus'', belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gadus'' is commonly not call ...

caught off the coast of

Bohuslän Bohuslän (; da, Bohuslen; no, Båhuslen) is a Swedish province in Götaland, on the northernmost part of the country's west coast. It is bordered by Dalsland to the northeast, Västergötland to the southeast, the Skagerrak arm of the North Sea ...

which suggests that ''G. rhomboides'' has now moved into

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

waters. A similar discovery a few weeks later in the same location reinforces this conclusion. This species inhabits

mud A MUD (; originally multi-user dungeon, with later variants multi-user dimension and multi-user domain) is a Multiplayer video game, multiplayer Time-keeping systems in games#Real-time, real-time virtual world, usually Text-based game, text-bas ...

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

s similar to those favoured by the

Norway lobster ''Nephrops norvegicus'', known variously as the Norway lobster, Dublin Bay prawn, ' (compare langostino) or ''scampi'', is a slim, orange-pink lobster which grows up to long, and is "the most important commercial crustacean in Europe". It is n ...

and burrows into inshore muddy sand. Its burrows often interconnect in complex patterns with those inhabited by other species of burrowing

megafauna In terrestrial zoology, the megafauna (from Greek μέγας ''megas'' "large" and New Latin ''fauna'' "animal life") comprises the large or giant animals of an area, habitat, or geological period, extinct and/or extant. The most common threshold ...

such as '' Callianassa subterranea'', ''

Cepola macrophthalma ''Cepola macrophthalma'' is a species of marine ray-finned fish belonging to the family Cepolidae, the bandfishes. It is found in the eastern Atlantic and Mediterranean from Senegal north to the British Isles. This species is known as the red ba ...

'', '' Lesueurigobius friesii'', and ''

Nephrops norvegicus ''Nephrops norvegicus'', known variously as the Norway lobster, Dublin Bay prawn, ' (compare langostino) or ''scampi'', is a slim, orange-pink lobster which grows up to long, and is "the most important commercial crustacean in Europe". It is n ...

''. These multi-species burrow complexes are very common in some localities.

Symbiosis

The setae on the antennae, mouthparts and legs of ''G. rhomboides'' are home to '' Triticella flava'', a species of

Bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

("moss animal"). The short lifespan of these

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

moss animals is synchronized so that they produce larvae just before ''G. rhomboides'' moults. These larvae then attach to the crab's newly emerged

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

References

{{Taxonbar, from=Q5237895 Goneplacoidea Crustaceans of the Atlantic Ocean Crustaceans described in 1758 Taxa named by Carl Linnaeus