NUCLEAR RDNA ITS SEQUENCE VARIATION IN THE TREMATODE GENUS ECHINOSTOMA - AN AID TO ESTABLISHING RELATIONSHIPS WITHIN THE 37-COLLAR-SPINE GROUP

The taxonomic history of members of the 37-collar-spine group within t he genus Echinostoma has been very confused. We obtained DNA sequence data from the nuclear rDNA ITS1, 5.8S and ITS2 of 7 nominal species be longing to this group, Echinostoma trivolvis (Cert, 1914), E. revolutu m (Frolich, 1802), E. caproni Richard, 1964, E. acaproni arasasingam e t nl. 1952, E. paraelzsei Lie & Basch, 1967, two African isolates, E. sp.I and E. sp.II, and of one 28-collar-spined echinostome, E. holtens e (,4sada, 1926). Five of the eight species n;ere clearly distinguisha ble using ITS data. Sequences from the remaining three tasa, E. cnpl o lzi, E. sp.ll and E. liel mere identical to one another and the group containing these laxa was distant from other 3'7-collar-spine species on a phylogenetic tree. E. tvizrolzris and E. pavaensei form a second, but less distinct group within the 35-collar-spine group. The resolut ion obtained using DNA sequencing will assist in the current reclassif ication of the group. It also provides a model for future work on sibl ing species.