Relationships among some ascaridoid nematodes based on ribosomal DNA sequence data.
The nuclear ribosomal DNA (rDNA) region spanning the first (ITS-1) and second (ITS-2) internal transcribed spacers was sequenced for 15 taxa of ascaridoid nematodes. The length of the ITS-1 and ITS-2 sequences in the 15 taxa ranged from 392-500 bp and 240 348 bp, respectively. While nucleotide variation of 0-2.9% in the ITS-1 and/or ITS-2 sequences was detected within taxa where multiple samples were sequenced, significantly higher level of nucleotide difference (9.4-66.6%) was detected between the taxa, except for Ascaris suum and A. lumbricoides whose taxonomic status remains uncertain. These interspecific differences were linked with the considerable size differences (0-108 bp) in the rDNA spacers. Phenograms based on the genetic differences among the 15 taxa showed some concordance with previous classification schemes derived from morphological data.
Zhu
X
X
The University of Melbourne, Werribee, Victoria, Australia.
Gasser
R B
RB
Jacobs
D E
DE
Hung
G C
GC
Chilton
N B
NB
D000818:Animals; D017164:Ascaris lumbricoides / Q000145:classification / Q000235:genetics*; D017165:Ascaris suum / Q000145:classification / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D018509:DNA, Helminth / Q000032:analysis*; D004275:DNA, Ribosomal / Q000032:analysis*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D017931:DNA Primers; D018509:DNA, Helminth; D004275:DNA, Ribosomal