Abstract
Influence of host on hook morphology, soluble protein profile and two polymorphic loci of the marine tapeworms, Hepatoxylon trichiuri and H. megacephalum were studied. It was found that hook lengths of the two parasites differed significantly and that they varied with the host species. Unweighted pair-group analysis of soluble protein similarity indices separated H. trichiuri and H. megacephalum into three groups by fish host species. Allozyme analyses revealed that a polymorphic locus, glucose-6-phosphate dehydrogenase, of H. trichiuri showed significant variations in the allelic and phenotypic frequencies between populations of parasites from different host species, but a second polymorphic locus, esterase, did not show any host-related variation. Owing to the small sample size of H. megacephalum statistical analysis was not carried out for the allozyme study. However, allelic frequencies of the Est locus differed significantly between the two parasites. The possible influence of fish hosts on parasite morphology, protein biochemistry and population genetics was discussed.