Contributions to the phylogeny of the Cyclophyllidea (Cestoda) inferred from mitochondrial 12S rDNA

A 314-bp fragment of the mitochondrial 125 rRNA gene from 21 cestodes speci es of eight families was synthesized by PCR with specially designed primers , These allowed amplification of parasite DNA without concomitant synthesis of host DNA. Phylogenetic trees were inferred from the sequence data using three methods (maximum parsimony, maximum Likelihood, and Fitch-Margoliash ). At the major nodes all three trees were similar. For the first time the genus Mesocestoides could be arranged into the Cyclophyllidea and a narrow relationship between the Mesocestoididae, Taeniidae, Hymenolepididae, Anopl ocephalidae, and Dipylidiidae was shown. Members of the families Catenotaen iidae and a cluster of two families (Hymenolepididae and Dilepididae) form two monophyletic groups which derive prior to the remaining families of thi s phylogenetic study. A third and a fourth clear monophyletic group were fo rmed by the Taeniidae and by the Mesocestoididae. A high degree of variatio n within the examined 304-bp fragment was observed between two isolates of Taenia taeniaeformis, supporting often discussed genetic heterogeneity with in this species. In contrast, only one nucleotide exchange was found in 23 isolates of Echinococcus multilocularis of various geographic origin, indic ating that this species is genetically homogenous.