Gammarus kesanensis sp. nov., a new blind amphipod species from Turkey (Amphipoda, Gammaridae), with a key to eyeless Gammarus species of Europe

A new blind species of freshwater amphipod, Gammarus kesanensis sp. nov., collected from Erikli Fountain, Keşan, Turkey, is described and illustrated. The new species belongs to Gammarus pulex- group and is the fourth blind species of the group reported from Europe and Turkey. A detailed morphological description and illustrations of the new species are given and differences from related species are discussed. In addition, a key to the blind/eyeless species of Gammarus genus of Europe is presented.