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Via morphological and molecular analysis, we describe a new species of taeniid from Patagonia (Argentina): Versteria cuja n. sp., parasitizing the Lesser grison Galictis cuja (Molina) (Carnivora: Mustelidae). This is the first report of a species of Versteria in Argentina and for a native mustelid. The new species (the third in the genus Versteria ) is proposed using an integrative taxonomic approach, based on traditional morphology (distinctive morphological and morphometric diagnostic characters), genetic distances and phylogeny based on molecular data, the distinct geographical distribution, and the different definitive host species. Versteria cuja n. sp. mainly differs from Versteria mustelae (Gmelin, 1790) (from Europe) in the number of testes (54-85 vs . 83-127 in V. mustelae ), the rostellum size (39-75 vs . 85-180 μm in V. mustelae ), the genital atrium size (170-420 vs . 68-91 μm in V. mustelae ) and in the hooks' shape. It also differs from the African species Versteria brachyacantha (Baer and Fain, 1951) by having smaller measurements regarding the main diagnostic characters, i.e. size of scolex, rostellum and suckers, number, size and shape of rostellar hooks, number of testes, and by having smooth cirrus ( vs . cirrus covered with hair-like bristles in V. brachyacantha ). Phylogenetical analysis using cox1 showed our specimens clustering with North American isolates of Versteria sp. in a well-supported American clade (mean genetic divergence 0.024), separated from another clade composed of different isolates of V. mustelae (0.093). The close relationship between the new species and the North American species, known as "zoonotic" Versteria sp., and responsible for fatal infections by metacestodes in free-ranging wildlife (rodents), captive primates and immunosuppressed people, lead us to think that the zoonotic potential of Versteria cuja n. sp. should not be discarded., Competing Interests: None., (© 2022 The Authors.)

The study reports a previously unknown apicomplexan (APXSc) parasite infecting wild scallops Aequipecten tehuelchus (d'Orbigny, 1842) from two separate areas (La Tapera and Punta Conos) of the San José gulf, in Patagonia Argentina. Histology, transmission electron microscope, molecular analyses and in situ hybridization were performed to describe the morphology of APXSc, and confirm its phylogenetic status. The prevalence of APXSc infection was 24% and 72% in scallops from La Tapera and Punta Conos, respectively. Seasonal variation was observed for scallops from La Tapera, recording highest prevalence in summer. A positive relationship between the presence of the APXSc and the size of the scallops was observed. A SSU rDNA consensus sequence of 1758 base pairs was generated which has a 94.8% identity to sequences obtained from a pathogenic apicomplexan parasite infecting Ostrea chilensis in New Zealand, but not closely related to other apicomplexans. The asexual reproduction, i.e. merogony, occurs in the Tehuelche scallop whilst the gamogonic and sporogonic stages were absent, suggesting a yet unknown definitive host. Severe host inflammation response involving fibroblast-like hemocytes surrounding the APXSc in the form of granuloma-like "swirls" is characteristic for this apicomplexan infection. Further studies are needed to reveal the life cycle, and presumable pathogenicity of APXSc., Competing Interests: The authors declare no competing interests., (© 2022 The Author(s).)