THE FRESH-WATER PLANARIAN DUGESIA-SICULA LEPORI FROM SARDINIA (PLATYHELMINTHES, TRICLADIDA)

Fissiparous strains of freshwater triclads of the Dugesia gonocephala group were collected from 12 localities in Sardinia all situated not m ore than 5 kilometers from the coast. Some environmental factors and t he sexual status of the specimens were noted at the time of collection , During the laboratory rearing 30% of individuals of each strain beca me sexual (ex-fissiparous individuals). All the examined strains showe d common karyological and morphological characteristics suggestive of the species Dugesia sicula Lepori. The chromosome complement, which wa s a constant 27 + 2-3 B chromosomes, was classified as aneutriploid, d ue to its clearly documented characteristics. The fissiparous populati ons of D. sicula appear to have a high degree of tolerance to variatio ns in environmental factors, especially temperature. Within the D. gon ocephala group this species has the broadest distribution in the Medit erranean region.