''Gammarus pulex'' 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 ...

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

found in

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

across much of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. It is a greyish animal, growing to long.

Description

Adult males of ''Gammarus pulex'' may reach a total length of , while females only grow to . The adults have a robust appearance; they are typically greyish with markings in dark brown or green. Individuals of the genus '' Dendrocometes'' are known to be parasites which reside on the gills of ''G. pulex''.

Distribution

''Gammarus pulex'' is found across most of

from the

Volga The Volga (; russian: Во́лга, a=Ru-Волга.ogg, p=ˈvoɫɡə) is the List of rivers of Europe#Rivers of Europe by length, longest river in Europe. Situated in Russia, it flows through Central Russia to Southern Russia and into the Cas ...

drainage in the east to the

British Isles The British Isles are a group of islands in the 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 and Outer Hebrides, the Northern Isles, ...

in the west. It is absent from Norway, parts of Scotland, and Ireland, although it was introduced to

Lough Neagh Lough Neagh ( ) is a freshwater lake in Northern Ireland and is the largest lake in the island of Ireland, the United Kingdom and the British Isles. It has a surface area of and supplies 40% of Northern Ireland's water. Its main inflows come ...

in the 1950s, where it is replacing the native ''

Gammarus duebeni ''Gammarus'' is an Amphipoda, amphipod crustacean genus in the family (biology), family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimu ...

''.

Taxonomic history

''Gammarus pulex'' was one of the species included in the 10th edition of

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

' ''

Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...

'', which marks the starting point for

zoological nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the In ...

, in 1758. Linnaeus called the species ''Cancer pulex'', the

specific epithet 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 ...

' being

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

for "

flea Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by ingesting the blood of their hosts. Adult fleas grow to about long, a ...

". His

description Description is the pattern of narrative development that aims to make vivid a place, object, character, or group. Description is one of four rhetorical modes (also known as ''modes of discourse''), along with exposition, argumentation, and narr ...

was, however, vague, and could apply to "nearly every species of amphipod". Some of Linnaeus' references refer to

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

species, while others refer to marine species. The application of the name was settled in 1970 by the redescription of the species and the selection of a

neotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

from a stream on the

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 ...

island of

Öland Öland (, ; ; sometimes written ''Øland'' in other Scandinavian languages, and often ''Oland'' internationally; la, Oelandia) is the second-largest Swedish island and the smallest of the traditional provinces of Sweden. Öland has an area ...

. The name ''Rivulogammarus'' has been used for a part of the genus ''

Gammarus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' when it is split into smaller genera, and ''G. pulex'' has sometimes been called ''Rivulogammarus pulex''. This name is, however, invalid under the

International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the ...

, since ''G. pulex'' is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of the genus ''Gammarus'', and the genus that contains it must therefore be named ''Gammarus''.

Parasites

''Gammarus pulex'' are known to be infected by at least three different species of acantocephalan parasites, ''

Pomphorhynchus laevis ''Pomphorhynchus laevis'' is an endo-parasitic acanthocephalan worm, with a complex life cycle, that can modify the behaviour of its intermediate host, the freshwater amphipod ''Gammarus pulex''. ''P. laevis'' does not contain a digestive tr ...

'', '' P. minutus'', and '' P. tereticollis''.

References

{{Taxonbar, from=Q492178

pulex ''Pulex'' is a genus of fleas. It comprises seven species. One is the human flea (''P. irritans''), and five of the others are confined to the Nearctic and Neotropical realms. Species ''Encyclopedia of Life'' lists seven species: *'' Pulex alva ...

Freshwater crustaceans of Europe Freshwater crustaceans of Asia Crustaceans described in 1758 Taxa named by Carl Linnaeus