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Title: MOLECULAR EVIDENCE FOR CRYPTIC SPECIES WITHIN CYLICODSTEPHANUS MINUTUS (NEMATODA: STRONGYLIDAE)

Author
item HUNG, G - UNIV MELBOURNE, AUSTRALIA
item CHILTON, N - UNIV MELBOURNE, AUSRALIA
item BEVERIDGE, IAN - UNIV MELBOURNE, AUSTRALIA
item ZHU, X - UNIV MELBOURNE, AUSTRALIA
item Lichtenfels, James
item GASSER, ROBIN - UNIV MELBOURNE, AUSTRALIA

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Strongyloid nematodes are a major cause of morbidity and mortality in equines in the United States. Resistance to antiparasitic drugs (currently the only means of controlling the nematode disease in horses) is common and alternative control methods for these parasites re needed to protect horses in the United States. Considerable research is underway worldwide to develop improved control strategies. This research requires the identification of the more than 51 nematode species that are parasitic in the large intestine and caecum of horses. This report provides the first DNA sequence evidence of cryptic species within a morphologically defined species, Cylicostephanus minutus. This information will stimulate additional research to more completely characterize and to find morphological features to identify the cryptic species. The information will be used to improve the accuracy of reports of drug trials and other control measures for these pathogens of horses.

Technical Abstract: The nucleotide sequences of the first and second internal transcribed spacers (ITS-1 and ITS-2) of nuclear ribosomal DNA were determined for adults of Cylicostephanus minutus from different geographical origins. The lengths of ITS-1 and ITS-2 sequences ranged from 370-372 bp and 215-216 bp, respectively. Pairwise sequence comparisons revealed that some individuals of C. minutus had identical ITS-1 and ITS-2 sequences, whereas others differed by 3.0% and 7.4% in both their ITS-1 and ITS-2 respectively. These levels of difference were higher than that between morphologically distinct species of Cylicostephanus, C. goldi and C. longibursatus (0.8% for the ITS-1 and 3.8% for the ITS-2). The data provide support for he proposal that C. minutus represents a complex of at least two species. In order to study the population genetic structure of C. minutus, a polymerase chain reaction linked single-strand conformation polymorphism (PCR-SSCP) technique was also established.