Description of two new species of Glypthelmins Stafford, 1905 (Digenea: Macroderoididae) in Rana spp. from Mexico, based on morphology and mtDNA and rDNA sequences

摘要

Glypthelmins Stafford, 1905 includes 29 putative species commonly found in the intestine and liver of anurans from all over the world but mainly in the Americas. Partial sequences of the cytochrome c oxidase subunit 1 ( cox 1), ribosomal internal transcribed spacer region 2 (ITS2) and the large subunit 28S rDNA gene were obtained and analysed using pairwise distance matrices and parsimony methods in order to characterise the interrelationships between 14 isolates of four nominal species of Glypthelmins recognised on morphological grounds. The highest intra-specific sequence divergence occurred in the cox 1 (18.53%) sequence, followed by that of the ITS2 (5.44%) and 28S (4.63%). Genetic variability was detected between the three isolates originally identified as G. facioi Brenes et al., 1959 from two localities in Mexico and one locality in Costa Rica. Sequence divergence exhibited among these isolates ranged from 10.70 to 11.22%, from 0.48 to 0.97% and from 1.33 to 1.88% for cox 1, ITS2 and 28S, respectively. Phylogenetic analysis combining all three data-sets generated a single most parsimonious tree. The three isolates of G. facioi form a clade, with an isolate collected from frogs in Veracruz State as the sister group to an isolate from Tabasco State + G. facioi from Costa Rica. The information derived from pairwise distance of independent data-sets plus the phylogenetic information indicate that each of the two isolates from Mexico, identified a priori as G. facioi, represent separate species. A re-examination of specimens was carried out and a re-evaluation made of the morphological characters to find reliable differences that had been overlooked. As a consequence, G. brownorumae n. sp. from Tabasco and G. tuxtlasensis n. sp. from Veracruz are described based on molecular and morphological differences.