A molecular phylogeny of the genus Ichthyocotylurus (Digenea, Strigeidae).
Three nucleotide data sets, two nuclear (ribosomal internal transcribed spacer regions 1 and 2, ITS1 and ITS2) and one mitochondrial (cytochrome c oxidase subunit 1, CO1), were analysed using distance matrix and maximum likelihood methods to determine the inter-relationships amongst the four species attributed to the genus Ichthyocotylurus Odening, 1969. Sequence data obtained from all gene loci investigated supported the position of Ichthyocotylurus variegatus as a species discrete from Ichthyocotylurus platycephalus. Phylogenetic analyses yielded congruent trees, with I. variegatus isolates comprising a common clade to which I. platycephalus constitutes a sister taxon. Ichthyocotylurus erraticus and Ichthyocotylurus pileatus were found to demonstrate a similarly close inter-specific relationship. The greatest intra-generic divergence occurred in the CO1 region (16% variability), with resultant disparities in three to eight encoded amino acids. PCR amplification yielded multiple ITS1 products for all Ichthyocotylurus spp. Analyses of equivalent-sized amplicons showed 5.4% intra-generic variation and several point mutations between I. variegatus isolates from different geographical localities and from different piscine hosts. The ITS2 locus was extremely conserved, with less than 1% variation between species. No intra-specific variation was recorded for any CO1 or ITS2 sequences.
Bell
A S
AS
Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK. a.bell@bio.gla.ac.uk
Sommerville
C
C
Tellervo Valtonen
E
E
D000818:Animals; D001483:Base Sequence; D018509:DNA, Helminth / Q000737:chemistry; D004275:DNA, Ribosomal / Q000737:chemistry; D005393:Fish Diseases / Q000469:parasitology; D005399:Fishes; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D014200:Trematoda / Q000145:classification* / Q000235:genetics; D014201:Trematode Infections / Q000469:parasitology / Q000662:veterinary
D018509:DNA, Helminth; D004275:DNA, Ribosomal