Morpho-karyological Types of Dugesia (Turbellaria, Tricladida) in Israel and Their Distribution Patterns

Populations of Dugesia in Israel have been classified on morphological and karyological criteria into 5 types. Two of these are morphologically similar to the Dugesia lugubris group (n = 4) but differ karyologically ( Types 1 and 2 : n=8), and three types are morphologically similar to the Dugesia gonocephala group ( n = 8) but two differ karyologically (Types 4 and 5: n = 9). The three ' gonocephala ' types are distributed in three distinct areas of Israel with little overlap, while the two ' lugubris ' types are found in springs of one of these areas, The Rift Valley, where special localised conditions prevail. Possible relationships between Types 3, 4 and 5 are discussed with particular reference to their karyotypes and the presence of supernumerary chromosomes in Type 5.