Molecular and morphological characterization of (Alegret, 1941) (Acanthocephala: Polymorphidae) in piscivorous birds from the Gulf of Mexico.

Adult specimens of (Alegret, 1941) were recorded from the intestines of the double-crested cormorant (Lesson) (type host) and brown pelican L. in two localities from Mexico: Celestún, Yucatan (south-eastern) and Punta Piedra, Tamaulipas (north-eastern). The specimens of are morphologically characterized by having a pipe-shaped body without swellings, the absence of small trunk spines between the two fields of spines on the foretrunk and a cylindrical proboscis with 14-16 rows of 10-12 hooks per row. Newly generated partial sequences of the mitochondrial cytochrome oxidase subunit 1 (1) gene were generated from adult isolates of from Mexico and compared with one sequence of and with sequences of other polymorphid acanthocephalans available in GenBank. Phylogenetic analyses based on maximum likelihood and Bayesian inference methods of the 1 dataset placed all the species of in a single clade, with weak support. The analyses of the 1 dataset placed Presswell, García-Varela & Smales, , as sister to the clade formed by , (Yamaguti, 1939), Presswell, García-Varela & Smales, and an unidentified species of from Japan. The newly generated 1 sequences of from piscivorous birds of Mexico formed a strongly supported clade with the published sequence of from the double-crested cormorant from the south-eastern coast of Mexico. The intraspecific genetic divergence among isolates identified as ranged from 0.0% to 2.2%. A 1 haplotype network inferred with 14 sequences revealed the presence of nine haplotypes, two of which were shared between the populations of piscivorous birds from the north-eastern and south-eastern coasts of Mexico and seven of which were unique. The fixation index between the populations from north-eastern and south-eastern Mexico was low (0.06949), which suggests genetic flow. This can be explained by the migration patterns of the brown pelican and the double-crested cormorant along the coasts of the Gulf of Mexico.