Morphometric and genetic evidence for cryptic diversity inGyrodactylus(Monogenea) infecting non-native European populations ofAmeiurus nebulosusandA. melas

Abstract

Gyrodactylid parasites were observed on non-native populations of North-American freshwater catfishes, Ameiurus nebulosus and Ameiurus melas (Siluriformes: Ictaluridae), at several sites in the Elbe River basin, Czech Republic, Europe. Using a combination of morphological and genetic analyses, the parasites infecting A. nebulosus were determined to be Gyrodactylus nebulosus, a North American parasite co-introduced to Europe along with its Ameiurus fish hosts. Subtle morphometrical differences, as well as seasonal variations, were observed among parasites collected from A. nebulosus and A. melas. The host-related variation was further supported through genetic analysis of the partial 18S rDNA, ITS1-5.8S-ITS2 and COI, showing 0.2, 3.0 and 4.8% divergence, respectively. Consistent genetic differences indicated there were two distinct genotypes. Subtle morphological differences associated with the shape of sickle toe, anchor root and ventral bar membrane, according to host species, also supported the description of a new cryptic species, Gyrodactylus melas n. sp., infecting A. melas. Multivariate morphometrical analysis of haptoral hard parts showed significant differences between the anchor lengths of G. nebulosus and G. melas n. sp. However, the measurements of the haptoral hard structures partially overlapped between species, limiting the usage of these parameters for species delineation.

Global Phylogeography of Salmonid Ectoparasites of the Genus Gyrodactylus, with an Emphasis on the Origin of the Circumpolar Gyrodactylus salmonis (Platyhelminthes: Monogenea)

“…The most significant morphological finding was that the size and shape of the taxonomically important marginal hook sickle were essentially identical among the specimens of G. salmonis identified during this study, those collected from O. clarkii during the redescription by Cone et al (1983), as well as those from the description of G. salvelini. While the anchors of North American specimens (66 µm) were smaller than those described for G. salvelini (87 µm; Kuusela et al 2008), considerable seasonal variation in anchor size, apparently influenced by water temperature, has been noted with other Gyrodactylus species (Mo et al 1991(Mo et al , 1993Ondračková et al 2020).…”

“…However, several studies have shown that variation in anchor size for Gyrodactylus spp. can occur seasonally and be quite substantial (Mo, 1991(Mo, , 1993Ondračková et al 2020), with differences up to ∼20 µm in the case of G. salaris (Mo, 1991). Furthermore, Ondračková et al (2020) found significant differences among the anchor sizes of Gyrodactylus specimens from different continents.…”

“…can occur seasonally and be quite substantial (Mo, 1991(Mo, , 1993Ondračková et al 2020), with differences up to ∼20 µm in the case of G. salaris (Mo, 1991). Furthermore, Ondračková et al (2020) found significant differences among the anchor sizes of Gyrodactylus specimens from different continents. While synonymization based on morphology alone would not be convincing in this case, with the only impediment being incongruent anchor sizes, the molecular data clearly connect G. salmonis and G. salvelini.…”

Phylogeny, species delimitation and ecological and morphological diversity of Characithecium (Monogenoidea: Dactylogyridae)

“…ITS and COI are known to have greater variability than ribosomal fragments (Bueno-Silva, 2012; Vanhove et al ., 2013), where many studies also observed divergence between morphological and molecular data. For Monogenoidea, the vast majority of these studies reports a cryptic diversity, which is accessed after using more variable genes (Benovics et al ., 2020; Ondračková et al ., 2020; Pinacho-Pinacho et al ., 2021).…”

Comparative Analysis of Parasite Load on Recently Established Invasive Pumpkinseed Lepomis gibbosus (Actinopterygii: Centrarchidae) in Europe

“…Many of these parasites are co-introduced together with their natural hosts [ 3 , 4 ]. These parasites are mainly specific to their non-native hosts and remain part of their parasite fauna and do not infect local species during the host’s range expansion [ 5 – 7 ]. In some cases, however, the non-native host species may distribute new, non-native parasites, that successfully infect local hosts [ 8 – 10 ].…”