Brachylecithum spp

Heneberg, Petr, Sitko, Jiljí, Casero, María & Rząd, Izabella, 2023, New molecular data help clarify the taxonomy of Central European avian Dicrocoeliidae Looss, 1899 (Trematoda: Plagiorchiida), International Journal for Parasitology: Parasites and Wildlife 22, pp. 276-299 : 286

3.1.4. Brachylecithum spp

The genus Brachylecithum is polyphyletic (see, e.g., the position of Dicrocoelium nested among Brachylecithum in Figs. 1–4 ), but sufficient support was not obtained for reclassifying individual clades. The analysis of additional species is needed.

The first clade is represented by Brachylecithum microtesticulatum Timon-David, 1955 . It can be distinguished from other Brachylecithum spp . by body size, the presence of a collar, longitudinal and transversal muscle fibers, and localization to the host pancreas. Previous authors agreed with the classification of this species as Brachylecithum or suggested reclassification of this species to Lyperosomum or establishing the genus Orthorchis for this species. Molecular evidence suggests that Brachyl. microtesticulatum is basal to Lutztrema , Eurytrema , and Corrigia ( Fig. 3B , nodal support 81%) and does not align with other Brachylecithum spp . ( Figs. 1 , Fig. 2 , Fig. 3 , Fig. 4 ). This species is rare in central Europe. Therefore, for the purpose of the molecular analyses, we collected it from several Larus fuscus from Portugal.

The second clade is represented by Brachyl. lobatum, Brachyl. strigis, Brachyl. glareoli, Brachyl. kakea , and Brachyl. capilliformis . All are localized to the gall bladder, rarely to the bile duct. The synonymy of Brachyl. lobatum with Brachyl. glareoli , suggested by Aldhoun et al. (2018), requires further attention by sequencing the DNA loci in multiple independently collected individuals of both these species and/or by whole mitochondrial genome sequencing. The CO1 sequences of Brachyl. lobatum and Brachyl. glareoli had evolutionary divergence of 0.015 –0.018 base substitutions per site ( Fig. 1 ). In comparison, the seven individuals of Brachyl. lobatum with known CO1 locus sequences differed by 0.000 –0.006 base substitutions per site. The two individuals of Brachyl. glareoli with known CO1 locus sequences had identical CO1 sequences.

The third clade is represented by Brachyl. laniicola , Brachylecithum asovi (Layman, 1926) , Brachylecithum transversogenitalis (Layman, 1922) , and Brachylecithum donicum (Issaitschikov, 1919) . All these species are localized to the bile ducts. Molecular evidence suggests that the genera Brachydistomum and Dicrocoelium are nested between the second and third clades. Note that there are issues with species identification of previously published Brachyl. kakea findings. Namely, the CO1 sequence KU212194 is from a correctly identified individual of Brachyl. laniicola ; KU212181 and KU212197 also represent Brachyl. laniicola but were identified as Brachyl. kakea ( Hildebrand et al., 2016) . The same reclassification applies to the 28S rDNA sequences from the two identical host individuals, namely, KU212178 and KU212180. Therefore, the claims on the clade formed by Brachyl. laniicola and Brachyl. kakea by Hildebrand et al. (2016) are incorrect. The core hosts of Brachyl. laniicola are shrikes, but DNA sequencing also confirmed its presence in Acrocephalus arundinaceus (e.g., OR426414). Molecular evidence shows that Brachyl. donicum from Apus apus and Oriolus oriolus represent the same species (e.g., Fig. 1 ).

Figures

Fig. 1. Maximum likelihood analysis of sequences of the CO1 DNA locus of Dicrocoeliidae. Bootstrap values (n = 1000) are indicated for nodal support. Black circles indicate new sequences. The scale-bar indicates the number of substitutions per nucleotide site.

Fig. 2. Maximum likelihood analysis of sequences of the ND1 DNA locus of Dicrocoeliidae. Bootstrap values (n = 1000) are indicated for nodal support. Black circles indicate new sequences. The scale-bar indicates the number of substitutions per nucleotide site.

Fig. 3. Maximum likelihood analysis of sequences of nuclear DNA loci (28S rDNA (A) and 18S rDNA (B)) of Dicrocoeliidae. Bootstrap values (n = 1000) are indicated for nodal support. Black circles indicate new sequences. The scale-bars indicate the number of substitutions per nucleotide site.

Fig. 4. Maximum likelihood analysis of sequences of the ITS2 DNA locus of Dicrocoeliidae. Bootstrap values (n = 1000) are indicated for nodal support. Black circles indicate new sequences. The scale-bar indicates the number of substitutions per nucleotide site.