Abstract

Distribution of blood fluke Aporocotyle spp. parasitizing Merluccius species from the coastsof South America (Peru, Chile and Argentina) constitutes an excellent opportunity to evaluate thegeographical amplitude in which a parasite can exploit the same host species. Phylogenetic analyses(partial sequences of SSU rDNA, LSU rDNa, and cox1 gene) were performed to characterize thegenetic lineage of Aporocotyle species described from South American Hake: Merluccius australis,M. gayi, and M. hubbsi. The Phylogenetic analyses (SSUrDNA and LSUrDNA) revealed an absenceof genetic variability in Aporocotyle obtained over a gradient of 6800 km, covering two oceans andthree closely related hosts. Consequently, the species infecting Merluccius spp. in South America isAporocotyle argentinensis Smith 1969, by priority law. Phylogeographic analysis suggests a pattern ofspatial differentiation and genetic population structure associated with the geographical distributionof the host’s species. A specimen with a haplotype found in M. gayi was collected from M. australisfrom Puerto Montt, and three worms (from Coquimbo, Constitución and Talcahuano, host M. gayi)harbored a haplotype found in M. australis + M. hubbsi, suggesting that the gene flow betweendifferent hosts and geographical distributions occurs when the distribution of adequate hosts overlaps,avoiding speciation in blood flukes from South American hakes.