Molecular phylogeny and systematics of the Echinostomatoidea Looss, 1899 (Platyhelminthes: Digenea)

Abstract

The Echinostomatoidea is a large, cosmopolitan group of digeneans currently including nine families and 105 genera, the vast majority parasitic, as adults, in birds with relatively few taxa parasitising mammals, reptiles and, exceptionally, fish. Despite the complex structure, diverse content and substantial species richness of the group, almost no attempt has been made to elucidate its phylogenetic relationships at the suprageneric level based on molecules due to the lack of data. Herein, we evaluate the consistency of the present morphology-based classification system of the Echinostomatoidea with the phylogenetic relationships of its members based on partial sequences of the nuclear lsrRNA gene for a broad diversity of taxa (80 species, representing eight families and 40 genera), including representatives of five subfamilies of the Echinostomatidae, which currently exhibits the most complex taxonomic structure within the superfamily. This first comprehensive phylogeny for the Echinostomatoidea challenged the current systematic framework based on comparative morphology. A morphology-based evaluation of this new molecular framework resulted in a number of systematic and nomenclatural changes consistent with the phylogenetic estimates of the generic and suprageneric boundaries and a new phylogeny-based classification of the Echinostomatoidea. In the current systematic treatment: (i) the rank of two family level lineages, the former Himasthlinae and Echinochasminae, is elevated to full family status; (ii) Caballerotrema is distinguished at the family level; (iii) the content and diagnosis of the Echinostomatidae (sensu stricto) (s. str.) are revised to reflect its phylogeny, resulting in the abolition of the Nephrostominae and Chaunocephalinae as synonyms of the Echinostomatidae (s. str.); (iv) Artyfechinostomum, Cathaemasia, Rhopalias and Ribeiroia are re-allocated within the Echinostomatidae (s. str.), resulting in the abolition of the Cathaemasiidae, Rhopaliidae and Ribeiroiinae, which become synonyms of the Echinostomatidae (s. str.); and (v) refinements of the generic boundaries within the Echinostomatidae (s. str.), Psilostomidae and Fasciolidae are made.

Molecular biological studies of adult and metacercarial stages of Petasiger exaeretus Dietz, 1909 (Digenea: Echinostomatidae)

“…The abovementioned five species have 19 collar spines rather than 27, and it is unlikely, therefore, that the Type 1 metacercaria belongs to any of these. Those species with 19 collar spines were elevated to full generic rank, as Neopetasiger Baschkirova, 1941, by Tkach et al (2016), which would represent the morphological and molecular separateness of these species. The cercaria samples isolated by Selbach et al (2014) also had 19 collar spines, so it is expected that the 28S rDNA sequences of Pet.…”

“…based on their morphology and 28S rDNA and nadI sequences. Recently, Tkach et al (2016) have provided a comprehensive molecular phylogeny of the Echinostomatoidea Looss, 1899, using 28S rDNA sequences, which included Petasiger spp.…”

Experimental investigation of alternative transmission functions: Quantitative evidence for the importance of nonlinear transmission dynamics in host–parasite systems

“…Ribeiroia ondatrae is a trematode in the family Echinostomatidae with a complex life cycle, sequentially infecting snails (Helisoma trivolvis), larval amphibians and finally amphibian-eating birds (Johnson, Sutherland, Kinsella, & Lunde, 2004;Tkach, Kudlai, & Kostadinova, 2016). Transmission of R. ondatrae from snails to amphibians occurs through direct infection by free-living aquatic parasite stages-cercariae-which then form encysted metacercariae in the amphibian that induce developmental malformations (Johnson, Lunde, Ritchie, & Launer, 1999).…”

Molecular and morphological characterization of Isthmiophora melis (Schrank, 1788) Luhe, 1909 (Digenea: Echinostomatidae) from American mink (Neovison vison) and European polecat (Mustela putorius) in Lithuania

“…The morphological identifi cation was based on the keys provided by Kozlov (1977) and Kostadinova and Gibson (2002). The systematics of the family Echinostomatidae and names of genera are used according to Tkach et al (2016).…”