New Contracaecum species (Nematoda, Anisakidae) parasitizing Ardea cocoi Linnaeus (Aves, Ardeidae) in a mixed infection: morphological and molecular studies in Argentina

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 Ardeacocoi (Ardeidae) in a locality from the Buenos Aires Province, Argentina. An integrativetaxonomic approach was used, involving phylogenetic analyses and the examination of diagnosticmorphological features in the studied specimens. Among other features, the new speciescan be morphologically distinguished by the papillae arrangement on the male tail: whileC. jorgei exhibits a simple morphotype A, C. cocoi sp. nov. presents an intermediate morphotypeB. Mainly, the possession of three adcloacal papillae pairs is a diagnostic feature separating thisnew species from the rest of the Contracaecum species. The cox2 mtDNA isolates exhibitedC. cocoi sp. nov. as a single node and grouped close to the clade formed by both speciesContracaecum micropapillatum and C. bancrofti. The other cox2 mtDNA sequences showed agreat concordance with C. jorgei. The K2P distances calculated for the cox2 mtDNA isolates ofC. cocoi sp. nov. displayed a distance of 0.12 with C. bancrofti, 0.13 with C. micropapillatum, and0.16 with C. jorgei. Contracaecum cocoi sp. nov. is proposed as a new taxon clearly supported byboth phylogenetic analysis and distinctive morphological features that distinguish it from itscongeners. The occurrence of C. cocoi sp. nov. together with C. jorgei in sympatric and syntopicconditions suggests that ecological or reproductive isolating mechanisms may be acting tomaintain distinct lineages in shared environments. New records, particularly those involvingintermediate and definitive hosts, will contribute to elucidating the distribution of these parasitesin the Americas and potentially lead to the discovery of new species.