Popolamento planariologico dei fiumi del nord Sardegna: 2. I cariotipi dei tridadi d'acqua dolce rinvenuti nel bacino idrografico del fiume Coghinas

Karyological and karyometric analyses were carried out on freshwater Triclad populations collected in 19 sites of the Coghinas catchment basin (North Sardinia), in order to identify the existing karyotypes and to establish their distribution. By samples collected 25 strains of thegonocephalagroup and 9 of thelugubris-polychroagroup were obtained, on the basis of morphological and reproductive (sexual/fissiparous) caracteristics of the specimens. Within thegonocephalagroup 177 specimens (168 sexual and 9 fissiparous) were examined and 4 karyotypes were found as follow: l) diploid karyotype with 2n=2x= 14 belonging toDugesia heptaspecies; 2) diploid 2n=2x=16, triploid 2n=3x=24 and aneuploid 2n=?x=32 karyotypes belonging toDugesia benazziispecies. The karyotype with 32 chromosomes, typical of both fissiparous and sexual specimens, is difficult to interpretate owing to the variations in chromosome morphology. All the karyotypes resulted variously coexisting and distributed. Within thelugubris-polychroagroup 71 specimens were examined; 2 karyotypes were identified both diploid with 2n=2x=8 respectively belonging toDugesia mediterraneaandDugesia polychroaspecies.