Potamon fluviatile

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Potamon fluviatile

Near Threatened  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Brachyura
Family: Potamidae
Genus: Potamon
Species:
P. fluviatile
Binomial name
Potamon fluviatile
(Herbst, 1785)
Found in western and southern Italy, Malta, Albania, parts of former Yugoslavia and much of Greece
Synonyms
  • Potamophilus edule [2]
  • Potamon edule [3]
  • Potamon edulis [4]
  • Thelphusa fluviatilis [4]
  • Cancer fluviatilis [5]

Potamon fluviatile is a freshwater crab found in or near wooded streams, rivers and lakes in Southern Europe. It is an omnivore with broad ecological tolerances, and adults typically reach 50 mm (2 in) in size during their 10–12 year lifespan. They inhabit burrows and are aggressive, apparently outcompeting native crayfish.

P. fluviatile has been harvested for food since classical antiquity, and is now threatened by overexploitation. Many of the island populations are particularly vulnerable, and the Maltese subspecies has become a conservation icon. A population in Rome may have been brought there before the founding of the Roman Empire.

Description

Seven round translucent spheres: inside some of them, a pair of compound eyes can be seen.
Eggs containing fully formed juvenile crabs

Adult Potamon fluviatile may reach a carapace length of 50 millimetres (2.0 in), with females being generally smaller than males.[6] As with other crabs, the body is roughly square, with the reduced abdomen tucked beneath the thorax. The thorax bears five pairs of legs, the first of which is armed with large claws.

The

larval stages inside the egg.[6]

Potamon fluviatile is edible,

ancient Greeks; it is probably this species which they depicted on medals found at Agrigento, Sicily.[9] More recently, the species was depicted on the 5¢ coin in the last series of Maltese coins before the introduction of the Euro there in 2007.[10]

Ecology

Potamon fluviatile has a generalist diet, feeding on vegetable debris, scraping

jays.[8] The most significant predator may be mankind, with individual prospectors able to catch 3,000 to 10,000 in one season.[8]

Adults occupy burrows, while smaller individuals shelter under stones. The entrances to the burrows may be more than 5 m (16 ft) from the stream's edge and are always above water level. The burrows may be more than 80 cm (31 in) long, and probably serve to protect the crabs from extreme cold.[8]

Potamon fluviatile is an aggressive species, mostly attacking with the larger right claw, since 90% of individuals are right-handed.[8]

In the

wetlands.[1]

Distribution

Evrotas River, near Sparta
– habitat for Potamon fluviatile

The natural range of Potamon fluviatile is highly

Balkan Peninsula from Dalmatia to the Axios River in Greece.[3] It is also found on a number of islands, including Sicily, Malta and Gozo, the Ionian Islands, Aegean Islands, Sporades and Andros in the Cyclades.[1] Although the species as a whole is widespread, it is declining in numbers, and these insular populations are particularly vulnerable.[1]

Italy

Potamon fluviatile is widely distributed in much of mainland Italy, especially in the provinces of Trento, Lombardy, Veneto, Liguria, Tuscany, Umbria, Lazio, Campania, Apulia, and Calabria, as well as on the island of Sicily.[1] Although it used to be found as far north as Lake Garda, P. fluviatile no longer occurs north of the River Po.[3]

In 1997 a population of P. fluviatile was discovered under the ruins of Trajan's Forum in the heart of Rome, living in canals built by the Etruscans which connect to the Cloaca Maxima.[13] Based on a genetic analysis, which demonstrated that these crabs were similar to those in Greece, researchers believe that they had been brought by the Greeks before the founding of the city, some 3000 years ago. The crabs' unusual size, up to 12 cm (4.7 in), and longevity (up to 15 years) are also interpreted as evidence of a long-established population, by analogy with island gigantism.[7]

Malta

On the island of Malta, Potamon fluviatile is rare and restricted to a few locations in the west of the island.[14] On Gozo, there is a single population which inhabits part of a valley only 700 metres (770 yd) long.[4]

Balkans

In the Balkan Peninsula, Potamon fluviatile is known to occur in

Evrotas rivers.[1][16]

In the

Kefalonia, Lefkada and Zakynthos.[1] In the Aegean Islands, it is found on Skiathos and Skopelos (Sporades), on Euboea and Skyros, and at a single site on Andros in the Cyclades.[1]

Taxonomy

Potamon fluviatile is at the western distributional limit of the genus

cryptic species,[3] and the population from the Peloponnese was described in 2010 as P. pelops.[18]

P. fluviatile was formerly divided into three subspecies: P. f. algeriense, P. f. berghetripsorum and P. f. fluviatile. The first two of these live in

infraspecific taxa, they are rarely used by scientists, and some have questioned directly the value of defining infraspecific taxa within P. fluviatile.[3] In 1990, the population on Malta was described as a separate subspecies, Potamon fluviatile lanfrancoi, and that taxon has become a conservation icon in Malta[14] following its legal protection in 1993,[4] although not all scientists recognise the taxon.[1]

References

  1. ^
    doi:10.2305/IUCN.UK.2008.RLTS.T134293A3933275.en
    . Retrieved 19 November 2021.
  2. ^
    Raffles Bulletin of Zoology
    . 17: 1–286.
  3. ^
    S2CID 25956853
    .
  4. ^ a b c d Jacqueline Debrincat & Patrick J. Schembri (2007). "Burrow density of the endangered Maltese freshwater crab Potamon fluviatile lanfrancoi at Lunzjata and Xlendi valleys, Gozo" (PDF). Xjenza. 11 (120301): 1–9.
  5. Bulletin of Zoological Nomenclature
    . 19: 232–252.
  6. ^
    doi:10.1111/j.1365-2427.1990.tb00290.x
    .
  7. ^
    Cosmos. June 8, 2007. Archived from the original
    on August 25, 2008. Retrieved December 11, 2009.
  8. ^ a b c d e f g Francesca Gherardi; S. Guidi & Marco Vannini (1987). "Behavioural ecology of the freshwater crab, Potamon fluviatile: preliminary observations". Investigación Pesquera. 51 (Suppl. 1): 389–402.
  9. JSTOR 1548843
    .
  10. ^ "Maltese Definitive Issue Coins - Second Series". Central Bank of Malta. Archived from the original on May 28, 2009. Retrieved March 15, 2010.
  11. doi:10.1111/j.1365-2427.1989.tb01097.x
    .
  12. doi:10.1080/11250009409355977
    .
  13. ^ "Photo in the News: "Ancient" Crabs Live on in Roman Ruins". National Geographic. June 4, 2007. Archived from the original on July 22, 2011. Retrieved March 17, 2010.
  14. ^ a b D. Capolongo & J. L. Cilia (1990). "Potamon fluviatile lanfrancoi, a new subspecies of a Mediterranean freshwater crab from the Maltese Islands (Crustacea, Decapoda, Potamidae)" (PDF). Annalen des Naturhistorischen Museums in Wien. 91 B: 215–224.
  15. ^
    doi:10.1017/S1755267209000797
    .
  16. ^ Eugene G. Maurakis; David V. Grimes; Lauren McGovern & Peter J. Hogarth (2004). "The occurrence of Potamon species (Decapoda, Brachyura) relative to lotic stream factors in Greece" (PDF). Biologia, Bratislava. 59 (2): 173–179.
  17. Raffles Bulletin of Zoology
    . Suppl. 16: 273–308.
  18. doi:10.1071/IS10014
    .
  19. ^ a b Gerhard Pretzmann (1983). "Die Süßwasserkrabben der Mittelmeerinseln und der westmediterranen Länder" (PDF). Annalen des Naturhistorischen Museums in Wien. 84 B: 369–387.

External links

Media related to Potamon fluviatile at Wikimedia Commons

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