Abstract
BackgroundRecent molecular studies have revealed high species diversity of Diplostomum in central and northern Europe. However, our knowledge of the distribution of Diplostomum spp. in the southern distributional range in Europe of the snail intermediate hosts (Lymnaea stagnalis and Radix spp.) is rather limited. This study aims to fill this gap in our knowledge using molecular and morphological evidence.MethodsNineteen fish species and six fish-eating bird species were sampled opportunistically in three regions (Catalonia, Extremadura and Aragon) in Spain. All isolates of Diplostomum spp. were characterised morphologically and molecularly. Partial sequences of the barcode region of the cox1 mitochondrial gene and complete sequences of the ribosomal ITS1-5.8S-ITS2 gene cluster were used for molecular identification of the isolates.ResultsIntegrated morphological and molecular analyses demonstrated the presence of three species among the larval and adult isolates of Diplostomum spp. sampled in Spain: Diplostomum spathaceum (in fish and birds), D. pseudospathaceum (in birds) and Diplostomum sp. (in fish) referred to as Clade Q sensu Georgieva et al. (Int J Parasitol, 43:57–72, 2013). We detected ten cox1 haplotypes among the isolates of D. spathaceum with only one haplotype shared with adult isolates from central and northern Europe. No specific geographic pattern of the distribution of the novel haplotypes was found.ConclusionThis first molecular exploration of the diversity of Diplostomum spp. in southern Europe indicates much lower species richness compared with the northern regions of Europe.
Highlights
Recent molecular studies have revealed high species diversity of Diplostomum in central and northern Europe
All infected fishes were collected in the Ebro Delta (Tarragona, Spain) with the exception of P. willkomii originating from the aquaculture centre of Villafranco del Guadiana (Badajoz, Spain) (Table 1)
It is worth noting that infections with metacercariae of Diplostomum spp. were detected in some (C. carpio and M. anguillicaudatus) and not in other relatively well-sampled species (Pseudorasbora parva, Gambusia holbrooki and Lepomis gibbosus) in the Ebro Delta and in one of the three S. glanis sampled in this locality
Summary
Recent molecular studies have revealed high species diversity of Diplostomum in central and northern Europe. Recent molecular studies linking cox and ITS15.8S-ITS2 sequences for larval and adult isolates, which were identified based on parasite morphology, have revealed high species diversity of Diplostomum in central and northern Europe [1,7]. Our knowledge of the distribution of Diplostomum spp. in the southern distributional range in Europe of the snail intermediate hosts (Lymnaea stagnalis and Radix spp.) is rather limited. No data exist for infections with Diplostomum spp. in the intermediate and definitive hosts in southern Europe. There is a lack of data from the intermediate fish hosts; only unidentified metacercariae of Diplostomum sp. were reported in Anguilla anguilla in the Rivers Ulla and Tea in Galicia [12]
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