Molecular analysis of polymorphic species of the genus Marshallagia (Nematoda: Ostertagiinae)

Abstract

Background: The genus Marshallagia (Family Haemonchidae, subfamily Ostertagiinae) contains multiple species of nematodes parasitising the abomasum (or duodenum) of ruminants, in particular of Caprinae. Male specimens have been described to be polymorphic with the frequent/major morphotype initially described in the genus Marshallagia while the minor/rare morphotype was initially often placed in the genus Grossospicularia. Due to common morphological features, certain pairs of morphotypes were suggested to belong to the same species such as Marshallagia marshalli/M. occidentalis. However, molecular evidence to confirm these pairs of morphotypes belonging to the same species is missing. Methods: In the present study, Marshallagia sp. were collected from domestic sheep in Uzbekistan. Male specimens were morphologically described with particular emphasis on the structure of the bursa copulatrix. After DNA isolation from morphologically identified specimens, PCRs targeting the ribosomal internal transcribed spacer 2 (ITS2) and mitochondrial cytochrome c oxidase subunit 1 (cox1) regions were conducted. After Sanger sequencing, maximum likelihood phylogenetic analyses and pairwise identities between sequences were calculated. Results: The major morphotypes of M. marshalli, M. schumakovitschi and M. uzbekistanica and the minor morphotypes M. occidentalis, M. trifida and M. sogdiana were identified and their morphology was documented in detail. ITS2 sequences showed little variation and did not allow diagnosing species. In contrast, phylogenetic analysis of cox1 sequences identified highly supported clusters and verified that M. marshalli, M. occidentalis and M. uzbekistanica are different morphotypes of the species M. marshalli while M. schumakovitschi and M. trifida represent distinct morphotypes of M. trifida. For M. sogdiana no corresponding major morphotype could be identified in the present study. Due to a large barcoding gap, comparison of cox1 sequences in terms of percent identity was sufficient to reliably assign the sequences to a particular species without phylogenetic analysis. Conclusions: The data presented here create a framework that will allow the classification of other members of the genus in the future and underline that parallel morphological and molecular analysis of specimens is crucial to improve the taxonomy of polymorphic species.

Genetic diversity of vector-borne pathogens in spotted and brown hyenas from Namibia and Tanzania relates to ecological conditions rather than host taxonomy

“…For D. repens , multiple cryptic species were identified which come from different geographic locations and may also have different host ranges, suggesting that species diversity of filarioid parasites is considerably underestimated [ 99 – 101 ]. For strongyle nematodes, the combination of morphological and molecular data revealed synonyms [ 102 , 103 ] as well as cryptic species [ 104 , 105 ].…”

Molecular Characterization of Mitochondrial Genome From Trichostrongylus Species (Nematoda: Trichostrongylidae) in Northern Iran

“…Another study in Uzbekistan was performed based on ribosomal (ITS2) and mitochondrial (Cox1) of Marshallagia sp. the result of the study indicate that ITS2 sequences had little variation, therefor the gene did not allow diagnosing species, while Cox1is more veri ed [31]. Ostertagia trifurcata and Marshallagia marshalli in China were evaluated by phylogenetic analysis of the complete mitochondrial genes.…”

“…Mt genomes are conserved and present large amounts of sequence data in the organisms, therefore mtDNA are used for evolutionary analyses, taxonomy, population genetics, and systematics studies [25,26,27]. There are few studies that have investigated the mitochondrial gene of Trichostrongylidae family, in which the mtDNA of the species of Marshallagia marshalli, Haemonchus placei, Haemonchus contortus, T. vitrinus, T. axei, Ostertagia trifurcate, and Teladorsagia circumcincta were evaluated for phylogenetic relationship and species identi cation [25,28,29,30,31,32,33]. Taxonomy studies of the nematodes based on sequences of coding mitochondrial genes are more accurate than non-coding ribosomal genes.…”

“…Taxonomy studies of the nematodes based on sequences of coding mitochondrial genes are more accurate than non-coding ribosomal genes. Meanwhile, the mitochondrial genomes are considered as suitable markers for population evolution studies [31,32], while the studies targeting the mtDNA for identi cation of Trichostrongylidae are very limited worldwide with even no single study on mitochondrial gene of the nematodes reported from Iran, so, the present study focused on molecular phylogenetic analysis based on cytochrome c oxidase subunit I (Cox1) mitochondrial gene of Trichostrongylus species in northern Iran.…”

Fish diversity in a doubly landlocked country - a description of the fish fauna of Uzbekistan using DNA barcoding

“…To date, studies on piscifauna have been based mainly on traditional morphological criteria and have not been comprehensively barcoded, except in our recent studies [48-50]. Recently, molecular identification has been applied to identify mainly nematodes among animal species [51].…”