Integrated taxonomy: traditional approach and DNA barcoding for the identification of filarioid worms and related parasites (Nematoda)

Coralie Martin,Michela Barbuto,Emanuele Ferri,Hubert Ferté,Andrea Galimberti,Shigehiko Uni,Ricardo Guerrero,Claudio Bandi,Maurizio Casiraghi,Odile Bain

doi:10.1186/1742-9994-6-1

Abstract

BackgroundWe compared here the suitability and efficacy of traditional morphological approach and DNA barcoding to distinguish filarioid nematodes species (Nematoda, Spirurida). A reliable and rapid taxonomic identification of these parasites is the basis for a correct diagnosis of important and widespread parasitic diseases. The performance of DNA barcoding with different parameters was compared measuring the strength of correlation between morphological and molecular identification approaches. Molecular distance estimation was performed with two different mitochondrial markers (coxI and 12S rDNA) and different combinations of data handling were compared in order to provide a stronger tool for easy identification of filarioid worms.ResultsDNA barcoding and morphology based identification of filarioid nematodes revealed high coherence. Despite both coxI and 12S rDNA allow to reach high-quality performances, only coxI revealed to be manageable. Both alignment algorithm, gaps treatment, and the criteria used to define the threshold value were found to affect the performance of DNA barcoding with 12S rDNA marker. Using coxI and a defined level of nucleotide divergence to delimit species boundaries, DNA barcoding can also be used to infer potential new species.ConclusionAn integrated approach allows to reach a higher discrimination power. The results clearly show where DNA-based and morphological identifications are consistent, and where they are not. The coherence between DNA-based and morphological identification for almost all the species examined in our work is very strong. We propose DNA barcoding as a reliable, consistent, and democratic tool for species discrimination in routine identification of parasitic nematodes.

Highlights

We compared here the suitability and efficacy of traditional morphological approach and DNA barcoding to distinguish filarioid nematodes species (Nematoda, Spirurida)
In order to provide a useful tool for easy identification of filarioid nematodes this work aims to answer the following questions: 1) which is the performance of DNA barcoding on filarioids and related nematodes? 2) which is the better marker for identification these organisms at the species level? 3) can DNA barcoding be a useful tool for detection of putative new species?
In spite of these difficulties, we have included in this study the most important filarioid parasites of humans and other animals, including Onchocerca volvulus, agent of human river blindness, Wuchereria bancrofti and Brugia malayi, agents of human tropical elephantiasis, Loa loa, agent of human ocular filariasis, Dirofilaria immitis, agent of heartworm disease of dogs and cats, plus a collection of specimens recovered from the tissues of wild animals such as bats, ungulates, monkeys, tropical toads, reptiles and birds, collected all around the world

Summary

Introduction

We compared here the suitability and efficacy of traditional morphological approach and DNA barcoding to distinguish filarioid nematodes species (Nematoda, Spirurida). The performance of DNA barcoding with different parameters was compared measuring the strength of correlation between morphological and molecular identification approaches. Molecular distance estimation was performed with two different mitochondrial markers (coxI and 12S rDNA) and different combinations of data handling were compared in order to provide a stronger tool for easy identification of filarioid worms. Molecular data have become widely used to aid rapid assessment of species diversity, and the DNA barcoding initiative [1] is one prominent line of research within this field, coordinated by the Consortium for the Barcode of Life (CBoL, http://barcoding.si.edu). Finding a balance between standardization, low costs and accuracy is difficult, and researchers have to take key decisions on the level of accuracy they want to get and the costs they can reasonably sustain

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