Molecular data reveal hidden diversity of the genus Clinostomum (Digenea, Clinostomidae) in Argentina, with the description of a new species from Ardea cocoi (Ardeidae)

Abstract

The genus Clinostomum has been recently a subject of a large number of molecular phylogenetic studies that have uncovered a larger species diversity than we thought. In Argentina, only two nominal species have been reported, namely C. detruncatum and C. marginatum. Three putative species represented by metacercariae were recently molecularly diagnosed, and there are at least two additional metacercarial morphotypes diagnosed on morphological grounds. Here, we molecularly characterized specimens of Clinostomum sampled from freshwater fishes and fish-eating birds from Argentina through mtDNA cytochrome c oxidase subunit I (COI). Unexpectedly, the phylogenetic analysis uncovered three new additional genetic lineages, two of them corresponding to metacercarial stages and another matching COI sequences of C. heluans Braun, 1899, being considered conspecific, whereas the others still require formal description. Additionally, we add a new host species for a lineage molecularly diagnosed in a previous study. The adult specimens recovered from A. cocoi in Buenos Aires Province represented a new species clearly distinguished from the two species previously reported in Argentina. Clinostomum detruncatum is distinguished from the new species by possessing a characteristic tenoidean uterus, and testes located more posteriorly. Clinostomum marginatum is morphologically similar but differs from the new species in having rounded ovary, posterior testis lobated, and lateral cirrus-sac and displacing the anterior testis, and vitelline follicles not extending beyond the caeca end. Our study raises the number of Clinostomum species in Argentina up to 10. We describe the new species herein.

Size does not matter: molecular phylogeny reveals one of the largest trematodes from vertebrates, the enigmatic Ithyoclinostomum dimorphum, as a species of Clinostomum (Trematoda: Clinostomidae)

“…A similar scenario can be found even at the species level, which can be evidenced by the case of Clinostomum marginatum (Rudolphi, 1819). Despite the fact that this species has been sequenced from isolates obtained from birds and fish in North America ( Caffara et al, 2011 ; Rosser et al, 2017 ), its specific assignment should be confirmed once isolates from the type locality in Brazil, are sequenced ( Pinto et al, 2015 ; Montes et al, 2021 ).…”

“…The models used were as follows: TVM+F+G4 for both ITS-1 and ITS2, and K2P+I for 5.8S, all included in the ribosomal gene cluster ITS1-5.8S-ITS2 alignment (3 partitions); TVM+F+I+G4 for the 28S dataset alone; TIM3+F+I+G4, TIM+F+G4, GTR+F+G4, for the 1st, 2nd and 3rd codon positions of the cox 1 dataset, respectively (3 partitions); GTR+F+G4, K2P+I, TVM+F+G4, TVM+F+I+G4, TN+F+G4, K3Pu+F+G4, TPM2+F+G4, for the ITS1, 5.8S, ITS2, 28S, cox 1 1st + 2nd + 3rd codon positions of the concatenated dataset (7 partitions). Outgroups were chosen based on previous phylogenetic studies ( Briosio-Aguilar et al, 2019 ; Rosser et al, 2020 ; Montes et al, 2021 ).…”

“…However, a proper classification that reflects the evolutionary history of the group is still in progress and far from being achieved, mainly because molecular data for some key taxa (type genera and species) is lacking. In fact, most information is available only for the species-rich Clinostomum ( Supplementary Table S1 ), including numerous unnamed lineages of this genus that are awaiting their formal description ( Montes et al, 2021 ).…”

Metacercariae in the brain ofErythrinuscf.erythrinus(Characiformes: Erythrinidae) from Iguazú National Park (Argentina): do they belong toDolichorchis lacombeensis(Digenea, Diplostomidae)?

“…The PCRs were made with GoTAQ Master Mix (Promega) according to the manufacturer's protocol. Amplification was done under conditions based on the protocols described for 28S and ITS by Tkach et al (2003), and for COI by Montes et al (2021b). Sequencing was performed on an ABI 3730XL sequencer by Macrogen Inc. (Korea).…”

Integrative analysis of new Clinostomum metacercariae (Digenea, Clinostomidae) using COI mtDNA and morphology rises the number of lineages found in South American freshwater fishes

“…Within the Americas, clinostomids exhibit several genetic lineages. Noteworthy contributions have significantly enriched the catalog of identified clinostomid lineages within Argentina (Montes et al, 2020; 2021). In Argentina there have been documented four species, namely Clinostomum detruncatum Braun, 1899, Clinostomum heluans, Braun, 1899 Clinostomum marginatum (Rudolphi 1819) Braun 1901 sensu stricto , and Clinostomum fergalliarii Montes, Barneche, Pagano, Ferrari, Martorelli, & Pérez Ponce de León, 2021.…”