Potamon potamios Olivier, 1804
Common names: Freshwater crab [En], Süßwasserkrabbe [De], Cangrejo de agua dulce [Es], Ποταμοκάβουρας [Gr], Eğirdir Gölü Tatlısu Yengeci, Yengeç [Tu]
IUCN Status: NT (Near Threatened)
Alanya, ANTALYA ● Turkey
Description: Relatively large freshwater crab. Depending on the subspecies, its carapace reaches a width of about 55 to 70 mm, a length of 44 to 57 mm and a height of 26 to 34 mm. The carapace is slightly convex, smooth and shiny. Its front side edge has many very small, rounded teeth. The forehead is steeply inclined and has two smooth, shiny, upper side lobe granular. The abdomen is elongated triangular in males with slightly convex sides; the abdomen of the female is wider, as with all crabs.
The two claws are quite large and may be slightly different. They have high cutting, closing and leave a gap occupied alternately with a larger, and three to four smaller nodes.
Seven subspecies of P. potamios have been recognised over the years mainly to recognise subpopulations that inhabit islands:
• P. p. subsp. cyprion Pretzmann, 1962 – Cyprus
• P. p. subsp. karamani Pretzmann, 1962
• P. p. subsp. karpathos Ghiavarini, 1934 – Karpathos island
• P. p. subsp. kretaion Ghiavarini, 1934 – Crete
• P. p. subsp. palaestinense Bott, 1967 – from Damascus basin and Jordan’ Rift Valley to the Sinai peninsula
• P. p. subsp. potamios Olivier, 1804
• P. p. subsp. schoenmanni Pretzmann, 1986 – Naxos island
Biology: Medium-sized crabs are nocturnal whereas the larger ones are diurnal and are active during daytime in the water and on the banks of the rivers.
Habitat: Its habitat includes diverse environments including streams, rivers and lakes and surroundings.
Distribution: This species has a wide but highly fragmented distribution, from the Mediterranean and Aegean islands of Greece (Karpathos, Rhodes and Naxos) and Crete to the semiarid inland regions in Turkey (southern coastal provinces of Muğla, Burdur, Isparta, Antalya, İcel, Adana, and Hatay), Syria, Jordan (Litani River basins) Lebanon, Israel, Palestine, Cyprus, and Egypt (Sinai peninsula).
Threats and protection: There is not much information on the population size and abundance of P. potamios in most parts of its range, but it would appear that populations of this species on the islands of Naxos and Cyprus are declining. In Cyprus, freshwater crabs are locally abundant in the numerous year-round small springs and seepages in the Akamas peninsula, and in the mountain streams of the Troodos mountains and Paphos Forest. However, freshwater crabs have disappeared from many parts of Cyprus probably as a result of the extensive use of DDT and other insecticides during the campaign against malaria. The use of less harmful insecticides in recent years has seen some recovery of certain populations of this species, but some must be presumed extinct in some areas.
Although the wide distribution and high number of records for this species might imply that it should be assessed as Least Concern, the balance of evidence indicates that populations of this species may nevertheless be under immediate and long-term threat from rapid anthropogenic changes affecting its habitat such as water diversion, drainage, habitat disturbance, over-harvesting, and pollution. This species is therefore assessed here as Near Threatened (NT) because it is possible that populations of P. potamios in parts of its range might be in danger of extirpation in the future, especially those on islands in the eastern Aegean or near centres of human population on the mainland from southern Turkey to the Sinai peninsula in Egypt. Therefore it may be close to qualifying as Vulnerable.
Cumberildge N., 2008. Potamon potamios. In: IUCN Red List of Threatened Species. Version 2012.2.