The genetic relationships among 11 taxa, belonging to the genus Contracaecum (C. osculatum
A, C. osculatum B, C. osculatum (s.s.), C. osculatum D, C. osculatum E, C. osculatum
baicalensis, C. mirounga, C. radiatum, C. ogmorhini (s.s.), C. margolisi) and Phocascoris
(Phocoscris cystophorae), parasites as adults of seals, were inferred from sequence
analysis 1519 bp) of the mitochondrial cytochrome c oxidase subunit II (mtDNA cox2)
gene. Phylogenetic analyses obtained from Parsimony (MP) and Neighbour-Joining (NJ)
K2P distance values generated similar topologies, each well supported at major nodes.
All analyses delineated two main clades: the first encompassing the parasites of the
phocid seals, i.e. the C. osculatum species complex, C. osculatum boicolensis, C.
mirounga and C. radiatum, with the latter two species forming a separate subclade;
the second including the parasites of otarids, i.e. C. ogmorhini (s.s.) and C. margolisi.
An overall high congruence between mtDNA inferred tree topologies and those produced
from nuclear data sets (20 allozyme loci) was observed. Comparison of the phylogenetic
hypothesis here produced for Controcaecum spp. plus Phocascaris with those currently
available for their definitive hosts (pinnipeds) suggests parallelism between hosts
and parasite phylogenetic tree topologies.