''Potamon ibericum'' is a Eurasian species of

freshwater crab Around 1,300 species of freshwater crabs are distributed throughout the tropics and subtropics, divided among eight families. They show direct development and maternal care of a small number of offspring, in contrast to marine crabs, which relea ...

. It is an omnivore that feeds on land, but returns regularly to the water, and can survive short periods of drought in burrows and under stones. Its

natural range Species distribution —or species dispersion — is the manner in which a biological taxon is spatially arranged. The geographic limits of a particular taxon's distribution is its range, often represented as shaded areas on a map. Patterns of ...

stretches from north-eastern Greece, around both sides of the Black Sea and to beyond the Caspian Sea; populations have also been introduced to southern France. It is included as a near threatened species on the IUCN Red List, and is included in the ''Red Data Book'' for Ukraine.

Description

''Potamon ibericum'' differs from other species in the genus in the form of the first

pleopod 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 ...

of the males – the organ used to transfer spermatophores. In ''P. ibericum'', the flexible zone of this appendage is widest near the middle, rather than V-shaped (as in '' P. fluviatile'' and '' P. rhodium'') or bilobed (as in '' P. potamios'').

Ecology and behaviour

The continued survival of ''P. ibericum'' generally requires a permanent body of water, although the crabs can survive short periods of drought by retreating under stones, or into deep

burrow An Eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of sh ...

s. These burrows may be several kilometres from the nearest body of water. They only breed in moving water, with copulation occurring in the warmer months, from June to October. ''Potamon ibericum'' is an omnivore, eating

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

, filamentous algae, and plant matter, as well as a variety of animals, including worms, amphipod crustaceans,

aquatic insect Aquatic insects or water insects live some portion of their life cycle in the water. They feed in the same ways as other insects. Some ''diving'' insects, such as predatory diving beetles, can hunt for food underwater where land-living insects c ...

larvae, molluscs, frogs and tadpoles, fish, and

carrion Carrion () is the decaying flesh of dead animals, including human flesh. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures, c ...

. It feeds on land during the night, and if the air is humid enough, also during the day. In the areas where it occurs, ''P. ibericum'' is a major food item for the European otter, ''Lutra lutra'', alongside a variety of fish species.

Distribution

The

of ''P. ibericum'' is wide, but highly fragmented. In Europe, it is present in the Danube and its tributaries in Bulgaria, as well as rivers in North Macedonia, north-eastern Greece (east of the Axios River), Cyprus and the European part of Turkey, and around the coast of the Black Sea through Ukraine to the Caucasus. Despite 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 ...

', the species does not occur on the Iberian Peninsula, which has no native freshwater crabs, but to Caucasian Iberia. The Asian part of its range extends across Turkey to Iran and Turkmenistan. Some sites that formerly held populations of ''P. ibericum'' have been subject to occasional

desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

, and the crab populations have been reduced or extirpated. The northern limit of the species, like that of its western relative, '' P. fluviatile'' is close to the January isotherm. ''Potamon ibericum'' was introduced to the

Cagne The Cagne is a river that flows through the Alpes-Maritimes department of southeastern France. Its source is near Coursegoules, and it flows into the Mediterranean Sea in Cagnes-sur-Mer. It is long. The Malvan Malvan (also written as Malwan ...

River in southern France between 1975 and 1983, when crayfish of the species '' Astacus leptodactylus'' were imported for

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

from Turkey. It is now found some downstream of that site, at the entrance to a series of

gorge A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tenden ...

s, in a part of the river that rarely dries out. A second population was discovered in the 1990s, from the Cagne site, in the

Hérault River Hérault (; oc, Erau, ) is a department of the region of Occitania, Southern France. Named after the Hérault River, its prefecture is Montpellier. It had a population of 1,175,623 in 2019.Saint-Guilhem-le-Désert. Neither population is considered

invasive Invasive may refer to: *Invasive (medical) procedure *Invasive species *Invasive observation, especially in reference to surveillance *Invasively progressive spread of disease from one organ in the body to another, especially in reference to cancer ...

. Another species of ''Potamon'' – '' P. fluviatile'' – has also been introduced to France, in the vicinity of Nice. Fossil crabs assigned to the species "''P. antiquum''" have been discovered in sediments of Pliocene– Pleistocene age in northern Hungary. That species was previously thought to represent the ancestor of several extant species, including ''P. fluviatile'' and ''P. ibericum'', but its young age and geographical location suggests that "''P. antiquum''" may represent specimens of ''P. ibericum'' from former populations beyond the species' current northern limit. Fossils assigned to ''P. ibericum'' from Vallesian sediments at Richardhof in the Vienna Basin suggest that the crabs in those sediments were predators of an extinct snail in the genus '' Melanopsis''.

Conservation

Despite its wide geographical range, ''P. ibericum'' is classified as near threatened on the IUCN Red List, as "it is possible that populations of ''P. ibericum'' in parts of its range might be in danger of extirpation in the future, especially those on islands or near centres of human population on the mainland". It may even approach a classification of

vulnerable Vulnerable may refer to: General * Vulnerability * Vulnerability (computing) * Vulnerable adult * Vulnerable species Music Albums * ''Vulnerable'' (Marvin Gaye album), 1997 * ''Vulnerable'' (Tricky album), 2003 * ''Vulnerable'' (The Used album) ...

. The species is listed in the ''Red Data Book'' for the Ukraine.

References

External links

*
''Potamon ibericum'' (Bieberstein, 1809)
Pan-European Species directories Infrastructure {{Taxonbar, from=Q812783 Potamoidea Freshwater crustaceans of Europe Freshwater crustaceans of Asia Crustaceans described in 1808