MOLECULAR DELINEATION OF CYLICOCYCLUS-NASSATUS AND CYLICOCYCLUS-ASHWORTHI (NEMATODA, STRONGYLIDAE)

The nucleotide sequences of the first internal transcribed spacer (ITS -1), 5.8S gene and second internal transcribed spacer (1TS-2) of ribos omal DNA have been determined for Cylicocyclus nassatus, C. ashworthi and C. insignis. Pairwise comparisons revealed sequence differences be tween the taxa ranging from 3.8 to 6.2% for the ITS-2 and 2.2-2.7% for the ITS-1. For the ITS-1, the level of the sequence difference betwee n C. ashworthi and C. nassatus (2.2%) was equivalent to that between C . nassatus and C. insignis (2.2%), indicating that C. ashworthi and C. nassatus represent separate species. Theoretical restriction maps wer e constructed from the sequence data, and a polymerase chain reaction- linked restriction fragment length polymorphism (PCR-linked RFLP) tech nique was established to unequivocally distinguish C. ashworthi from C . nassatus. (C) 1997 Australian Society for Parasitology.