Description of Saccocoelioides miguelmontesi n. sp. (Digenea: Haploporidae) from characid fishes in the Iguazu River Basin based on morphological and molecular evidence

Abstract

Here we describe a new species of the genus Saccocoelioides found parasitizing Astyanax dissimilisGaravello & Sampaio, Psalidodon bifasciatus (Garavello and Sampaio) and Bryconamericus ikaaCasciotta, Almirón & Azpelicueta from the Iguazu National Park, Misiones province, Argentina.Saccocoelioides miguelmontesi n. sp. was studied based on morphological and molecular (28SrDNA and COI mtDNA sequences) data. The COI mtDNA tree indicated that the specimenscollected from the three fish hosts are conspecific, with an intragroup p-distance of 0%. The newspecies shows an intermediate morphological configuration between the diminutive and robustforms described for Saccocoelioides by Curran (2018). Although, in the 28S rDNA tree, it is placedin a well-supported clade with the two robust species analysed (S. elongatus and S. magnus;p-distance of 1 and 2%, respectively), it differs from the robust group by the range of body size,mature egg size, oral and ventral sucker size, sucker ratio, oral sucker to pharynx ratio, and postcecal or post-testis/body length percentage. Our results led us to redefine the robust group ashaving eggs shorter or equal in length to the pharynx. Saccocoelioides miguelmontesi n. sp. the 10thspecies reported from Argentina and the 7th species within the robust group.