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Logotyp för Naturhistoriska riksmuseet
Logotyp för Naturhistoriska riksmuseet

Diversity and evolution of nematodes

Nematodes, or roundworms, are one of those groups of animals that we humans do not notice in our daily lives, but that affect us in many different and considerable ways. Nematodes are also one of the largest, most broadely distributed and speciose groups of multicellular animals. They occur in nearly all types of habitats and exhibit an incredible diversity of lifestyles.

Forskningsområden: Zoologi

Forskningsämnen: Biodiversitet, Evolution, Fylogeni, Taxonomi & artbeskrivning

Project overview

Project period: 2011 - ongoing

Participating departments from the museum: Zoology

Nematodes are the most numerous multicellular animals on the planet and play an important role in nature and human life, in particular as parasites of humans, and as pests of crops and farmed animals. Naturally, due to their medical and agricultural importance, parasitic nematodes attract the majority of scientific attention, while the rest of Nematoda remain poorly studied.

Comprehensive understanding of the origin and evolution of nematodes cannot be achieved without good knowledge of the biology of free-living species, which can only be accomplished by combining classical zoological methods with modern tools in molecular systematics and bioinformatics.

Project description

There are about 28 000 species of nematodes described, while the total estimated number of species is between 100 000 and several millions. We focus our research on poorly known groups of nematodes, in particular those inhabiting deep sea, deserts, tropical rain forest, sea ice or are symbionts of other animals. Naturally, such poorly studied environments often harbour unknown species that we describe as new to science.

By using morphological (light and scanning electron microscopy) and molecular (single genes, transcriptomes and genomes) data we reconstruct the relationships between different groups of nematodes and how they evolve in different environments. We even study fossil nematodes that are found in amber and in Rhynie chert (lower Devonian deposits). Sometimes we also investigate the biology of particularly interesting species.

For example, we study how fast nematodes mutate under extreme conditions in the deserts, or which mode of reproduction (sexual or asexual) is more successful for nematodes. Another topic of particular interest is the diversity of parasitic nematodes that infect invertebrate animals and how they are related to their free-living ancestors.


Selected publications

  • Ahmed, M., Roberts, N.G., Adediran, F., Smythe, A.B., Kocot, K.M. & Holovachov, O. (2022). Phylogenomic analysis of the phylum Nematoda: conflicts and congruences with morphology, 18S rRNA and mitogenomes. Frontiers in Ecology and Evolution 9, 769565. External link.
  • Ahmed, M. & Holovachov, O. (2021). Twenty years after De Ley & Blaxter – how far did we progress in understanding the phylogeny of the phylum Nematoda? Animals 11, 3479. External link.
  • Smythe, A.B., Holovachov, O. & Kocot K.M. (2019). Improved phylogenomic sampling of free- living nematodes enhances resolution of higher-level nematode phylogeny. BMC Evolutionary Biology 19, 121. External link.
  • Holovachov, O., Haenel, Q., Bourlat, S.J. & Jondelius, U. (2017). The choice of taxonomy assignment approach has strong impact on the efficiency of identification of OTUs in marine nematodes. Royal Society Open Science 4, 170315. External link.

Project members

Sven Boström | Research associate

Enheten för Zoologi

Mohammed Ahmed | ZOO (2019–2022)

External participants

Project manager

Oleksandr Holovachov

Senior Curator



Resarch Areas: Zoology

Research Subjects: Biodiversity, Evolution, Phylogeny, Taxonomy & Species description

Page manager: Johannes Bergsten