Goneplax rhomboides
Encyclopedia
Goneplax rhomboides is a species
of crab
. It is known by the common name
angular crab because of its angular carapace
. Although it is also called the square crab, its shell is in fact more trapezoidal than square
(or rhomboidal
, as its scientific name
might suggest). This species is also known as the mud-runner because they are able to run away quickly when threatened.
and the Mediterranean Sea
from the North Sea
to southern Africa
and the Indian Ocean
coast of South Africa
. Waters off Shetland constitute the northern boundary of its range, and in 2008, marine biologists
from the University of Gothenburg discovered one intact in the stomach of a cod
caught off the coast of Bohuslän
which suggests that G. rhomboides has now moved into Swedish
waters. A similar discovery a few weeks later in the same location reinforces this conclusion.
This species inhabits mud
dy habitat
s similar to those favored by the Norway lobster and burrows into inshore muddy sand. Its burrows often interconnect in complex patterns with those inhabited by other species of burrowing megafauna
such as Callianassa subterranea
, Cepola macrophthalma
, Lesueurigobius friesii
, and Nephrops norvegicus. These multi-species burrow complexes are very common in some localities.
. It likewise has seta
e on its antennae
and mouthparts.
Females have short chelipeds 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. angulata, a similar species sharing at least part of its range. Its eyes are on the end of long, retractable eye stalks.
("moss animal"). The short lifespan of these symbiotic
moss animals is synchronized so that they produce larvae just before G. rhomboides moult
s. These larvae then attach to the crab's newly-emerged exoskeleton
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
. It is known by the common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
angular crab because of its angular carapace
Carapace
A carapace is a dorsal 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 underside is called the plastron.-Crustaceans:In crustaceans, the...
. Although it is also called the square crab, its shell is in fact more trapezoidal than square
Square (geometry)
In geometry, a square is a regular quadrilateral. This means that it has four equal sides and four equal angles...
(or rhomboidal
Rhombus
In Euclidean geometry, a rhombus or rhomb is a convex quadrilateral whose four sides all have the same length. The rhombus is often called a diamond, after the diamonds suit in playing cards, or a lozenge, though the latter sometimes refers specifically to a rhombus with a 45° angle.Every...
, as its scientific name
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...
might suggest). This species is also known as the mud-runner because they are able to run away quickly when threatened.
Range and habitat
G. rhomboides is found in the northeastern Atlantic OceanAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
from the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
to southern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
coast of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. Waters off Shetland constitute the northern boundary of its range, and in 2008, marine biologists
Marine biology
Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. 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 classifies species based on the environment rather...
from the University of Gothenburg discovered one intact in the stomach of a cod
Cod
Cod is the common name for genus Gadus, belonging to the family Gadidae, and is also used in the common name for various other fishes. Cod is a popular food with a mild flavor, low fat content and a dense, flaky white flesh. Cod livers are processed to make cod liver oil, an important source of...
caught off the coast of Bohuslän
Bohuslän
' is a Swedish traditional province, or landskap, situated 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 to the west, and the county of Østfold in Norway to the north...
which suggests that G. rhomboides has now moved into Swedish
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
waters. A similar discovery a few weeks later in the same location reinforces this conclusion.
This species inhabits mud
Mud
Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone . When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds...
dy habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s similar to those favored by the Norway lobster and burrows into inshore muddy sand. Its burrows often interconnect in complex patterns with those inhabited by other species of burrowing megafauna
Megafauna
In terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...
such as Callianassa subterranea
Callianassa subterranea
Callianassa subterranea is a species of burrowing ghost shrimp. This species is known by such generic common names as "mud shrimp" and "ghost shrimp".-Description:...
, Cepola macrophthalma
Cepola macrophthalma
Cepola macrophthalma is a fish of the of the bandfish family Cepolidae. It is found in the eastern Atlantic and Mediterranean from Senegal north to Norway...
, Lesueurigobius friesii
Lesueurigobius friesii
Lesueurigobius friesii is a species of goby....
, and Nephrops norvegicus. These multi-species burrow complexes are very common in some localities.
Physical description
G. rhomboides is a relatively small, distinctive-looking crab that ranges from yellowish-white, to orange, to reddish, to vivid pink in color. It has a smooth, quadrangular, strongly convex carapace that is much broader than it is long. It has long, slender pereiopods with margins of propodus and dactylus bristlesSeta
Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....
. It likewise has seta
Seta
Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....
e on its antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
and mouthparts.
Females have short chelipeds 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. angulata, a similar species sharing at least part of its range. Its eyes are on the end of long, retractable eye stalks.
Symbiosis
The setae on the antennae, mouthparts and legs of G. rhomboides are home to Triticella flava, a species of BryozoaBryozoa
The Bryozoa, also known as Ectoprocta or commonly as moss animals, are a phylum of aquatic invertebrate animals. Typically about long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia...
("moss animal"). The short lifespan of these symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
moss animals is synchronized so that they produce larvae just before G. rhomboides moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
s. These larvae then attach to the crab's newly-emerged exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
.