Mediterranean Freshwater Crab

Description

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. Adult Potamon fluviatile may reach a carapace length of 50 millimetres (2.0 in), with females being generally smaller than males. 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 life span of P. fluviatile is typically 10–12 years. Moulting does not occur in winter. Mating lasts between 30 min and 21 hours, with spawning usually taking place in August. Females carry the eggs on their pleopods (appendages on the abdomen) until they hatch directly into juvenile crabs, having passed through the larval stages inside the egg. Potamon fluviatile is edible, as indicated by its alternative specific epithet edulis, and was known to the ancient Greeks; it is probably this species which they depicted on medals found at Agrigento, Sicily. 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. The natural range of Potamon fluviatile is highly fragmented, and covers parts of many countries with a Mediterranean coastline. It is found in mainland Italy and on the Balkan Peninsula from Dalmatia to the Axios River in Greece. 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. Although the species as a whole is widespread, it is declining in numbers, and these insular populations are particularly vulnerable. Potamon fluviatile is at the western distributional limit of the genus Potamon. Other species in the genus occur through Eastern Europe and the Middle East, and across Central Asia as far east as northwestern India.