Morphological and molecular characterization of an enigmatic clinostomid trematode (Digenea: Clinostomidae) parasitic as metacercariae in the body cavity of freshwater fishes (Cichlidae) across Middle America

Abstract

The family Clinostomidae Lühe, 1901 contains 29 species allocated to seven genera, of which Clinostomum Leidy, 1856 is the most diverse, with c. 14 valid species. The diversity of Clinostomum has been assessed, combining morphological and molecular data. The genetic library for species in this genus has increased steadily, although there is little or no information for the other genera included in the family. Molecular phylogenetic relationships among the genera of clinostomids have not been assessed, and their classification is still based on morphological traits. The monotypic Ithyoclinostomum was described from a fish-eating bird in Brazil, and its metacercariae have been found in several locations in South America, parasitizing erythrinid freshwater fishes. We collected unusually large metacercariae from the body cavity of cichlids in several locations across Middle America. These metacercariae exhibited some resemblance to Ithyoclinostomum, although several differences prevent their inclusion in Ithyoclinostomum dimorphum, casting doubt on their taxonomic identification. The main objective of this paper was to characterize the metacercariae collected in cichlids using both morphology and molecular data from three molecular markers, and to assess the molecular phylogenetic relationships among the genera of Clinostomidae to establish the position of the newly generated sequences. We took a conservative position and tentatively placed the metacercariae as belonging to Ithyoclinostomum.

Patterns ofClinostomum marginatuminfection in fishes and amphibians: integration of field, genetic, and experimental approaches

“…in Brazil. This opinion is supported by the most recent descriptions of four additional new species from North America (Briosio-Aguilar et al , 2018; Rosser et al ., 2018).…”

“…Although trematodes in the genus Clinostomum are broadly distributed geographically and have been studied extensively, the taxonomy of this group has been the subject of extensive debate and discussion. Thus far, there are 31 recognized species of Clinostomum recorded from all continents other than Antarctica (see supplementary tables 1–3), of which 20 include some degree of support using genetic techniques (Locke et al , 2015; Caffara et al , 2017; Briosio-Aguilar et al ., 2018; Rosser et al ., 2018; Sereno-Uribe et al ., 2018). For the 14 species reported in North America (see supplementary table 3), differentiation among species is often believed to differ based on their use of second intermediate hosts, with nine species infecting only fishes, one infecting only amphibians, and two using both host groups.…”

Molecular data show Clinostomoides Dollfus, 1950 is a junior synonym of Clinostomum Leidy, 1856, with redescription of metacercariae of Clinostomum brieni n. comb.

“…Moreover, the identification of C. brieni by these authors was questioned by Briosio-Aguilar et al . (2018) because of the close relationship of its 28S sequence to data from Clinostomum . It is also relevant that the material sequenced by Athokpam et al .…”

“…A combination of molecular and morphological approaches is a useful way to resolve situations like this, as has already been shown in other clinostomids, i.e. Clinostomum Leidy, 1856 (Caffara et al ., 2011; Sereno-Uribe et al ., 2013), Euclinostomum Travassos, 1928 (Senapin et al ., 2014; Caffara et al ., 2016), Odhneriotrema Travassos, 1928 (Woodyard et al ., 2017) and Ithyoclinostomum Witenberg, 1925 (Briosio-Aguilar et al ., 2018). However, few DNA sequences from Clinostomoides are currently available for comparison.…”

Molecular and Histopathological Data on Levisunguis subaequalis Curran, Overstreet, Collins & Benz, 2014 (Pentastomida: Eupentastomida: Porocephalida: Porocephaloidea: Sebekidae: Sebekinae) from Gambusia affinis in Alabama, USA

“…To date, only Barton and Morgan (2016) and Woodyard et al (2019a) provide 18S, 28S, and COI sequence data from the same specimens for 4 of the 141 currently described pentastomid species for the analyses carried out in the present study. While phylogenetic analyses using concatenated ribosomal and mitochondrial sequence data are increasingly being used for phylogenetic inference in other parasitic groups as evidenced by recent works on species ranging from Clinostomidae (Caffara et al, 2016;Woodyard et al, 2017;Briosio-Aguilar et al, 2019) to Emeriidae (Ogedengbe et al, 2018;Woodyard et al, 2019b), the present molecular data from pentastomids are not suitable for such analyses. While there are over 141 described pentastomid species belonging to 26 genera (Christoffersen and de Assis, 2013), molecular data, including the data from the present study, are publicly available for only 14 species from 11 genera.…”