Abstract This study provides the description of a new species of Anisakidae, Contracaecum cocoi sp. nov., as well as the record of Contracaecum jorgei , both species parasitizing the Cocoi heron Ardea cocoi (Ardeidae) in a locality from the Buenos Aires Province, Argentina. An integrative taxonomic approach was used, involving phylogenetic analyses and the examination of diagnostic morphological features in the studied specimens. Among other features, the new species can be morphologically distinguished by the papillae arrangement on the male tail: while C. jorgei exhibits a simple morphotype A, C. cocoi sp. nov. presents an intermediate morphotype B. Mainly, the possession of three adcloacal papillae pairs is a diagnostic feature separating this new species from the rest of the Contracaecum species. The cox2 mtDNA isolates exhibited C. cocoi sp. nov. as a single node and grouped close to the clade formed by both species Contracaecum micropapillatum and C. bancrofti. The other cox2 mtDNA sequences showed a great concordance with C. jorgei. The K2P distances calculated for the cox2 mtDNA isolates of C. cocoi sp. nov. displayed a distance of 0.12 with C. bancrofti , 0.13 with C. micropapillatum , and 0.16 with C. jorgei. Contracaecum cocoi sp. nov. is proposed as a new taxon clearly supported by both phylogenetic analysis and distinctive morphological features that distinguish it from its congeners. The occurrence of C. cocoi sp. nov. together with C. jorgei in sympatric and syntopic conditions suggests that ecological or reproductive isolating mechanisms may be acting to maintain distinct lineages in shared environments. New records, particularly those involving intermediate and definitive hosts, will contribute to elucidating the distribution of these parasites in the Americas and potentially lead to the discovery of new species.
Garbin et al. (Thu,) studied this question.