''Diogenes pugilator'' is a

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

hermit crab Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an a ...

, sometimes called the small hermit crab or south-claw hermit crab. It is found from the coast of

Angola , national_anthem = "Angola Avante"() , image_map = , map_caption = , capital = Luanda , religion = , religion_year = 2020 , religion_ref = , coordina ...

to as far north as 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 ...

, and eastwards through 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 ...

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, ...

and

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

. Populations of ''D. pugilator'' may be kept in check by the

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

y crab '' Liocarcinus depurator''.

Description

Like other hermit crabs, ''D. pugilator'' conceals its soft abdomen inside an empty gastropod mollusc shell; the abdomen is twisted to fit the contours of the shell. 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 und ...

protects the anterior part of the crab and can be up to long; it is squarish in shape, has triangular projections along the front edge, and is clad with hairs on the front two corners. The eyes are on stalks which are about half as long as the width of the carapace. The left chela (claw) is very much larger than the right one, and both claws are covered with short hairs. The chelae and other legs can be contracted into the entrance of the shell.

Distribution and habitat

''D. pugilator'' is native to the temperate and subtropical eastern Atlantic Ocean. Its range extends from the southern

southwards to Angola, the

, the

and the

. Its northern limit was at one time thought to be Swansea in South Wales, but it has since been found as far north as

Anglesey Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a Local government in Wales, principal area known as the Isle of Anglesey, that includes Holy Island, Anglesey, Holy Island across the narrow Cymyran Strai ...

, and the coasts of southwestern Ireland. It is found on soft substrates from the shallow sub-tidal to depths of as much as , but is most common in shallow water.

Ecology

This is a small hermit crab which tends to occupy shells of the netted dog whelk ''

Tritia reticulata ''Tritia reticulata'', common name the "netted dog whelk", is a species of small European sea snail, a marine gastropod mollusc in the family Nassariidae, the dog whelks or nassa mud snails. Description The length of the shell varies betw ...

''. These crabs are often present on flattish beaches composed of medium to fine grained sand where the waves sweep up the shore. When exposed, they rapidly bury themselves in the sand, using the enlarged left chela to stabilise themselves in the wet sand and limit the extent to which they are rolled about by the waves. Near

Cádiz Cádiz (, , ) is a city and port in southwestern Spain. It is the capital of the Province of Cádiz, one of eight that make up the autonomous community of Andalusia. Cádiz, one of the oldest continuously inhabited cities in Western Europe, ...

in southern Spain, there are three species of hermit crab, ''D. pugilator'', '' Paguristes eremita'' and '' Pagurus forbesii''. Of these, ''P. eremita'' is the biggest and strongest, and makes use of the most robust gastropod shells with the widest apertures. ''D. pugilator'' is the most numerous but tends not to use the shells of the most common gastropod, '' Turritella turbona'', which are used preferentially by ''P. forbesii''. ''D. pugilator'' instead uses the less common ''Tritia reticulata'', even when the crab's carapace is so large that it overlaps the shell's aperture.

References

External links

* {{Taxonbar, from=Q3933877 Diogenidae Crustaceans of the Atlantic Ocean Crustaceans described in 1829