Molecular Phylogenetics of Fish Parasites

Molecular phylogenetics of fish parasites applies DNA sequence data to reconstruct evolutionary relationships among parasitic taxa infecting fish hosts. By analysing markers such as ribosomal RNA genes and mitochondrial loci, researchers can clarify species boundaries, reveal cryptic diversity and trace historical host–parasite associations. This approach has overturned many morphology-based classifications, demonstrating that traditional characters of attachment organs and proglottid anatomy often mask deep genetic divergences. Studies now integrate phylogenetic trees with biogeographical and ecological data to explore how host specificity, life-cycle complexity and environmental change drive parasite evolution. The resulting frameworks support both fundamental insights into coevolutionary processes and practical applications in aquaculture biosecurity, conservation of wild fish stocks and monitoring of invasive parasites. Globally, molecular phylogenetics has enabled rapid detection of emerging fish-borne pathogens, informed targeted treatments and guided policies for translocation and trade of live fish.

Research from Nature Portfolio

A recent study on freshwater prawns used full-length 28S rRNA sequencing to characterise Temnocephalidae flatworms associated with Macrobrachium australiense. Phylogenetic analyses revealed that prawn symbionts form a distinct clade, separate from previously described Australian species, indicating long-term host specificity and an underappreciated diversity of temnocephalid lineages. Morphological examination under scanning electron microscopy corroborated the molecular delimitations, illustrating concordance between ultrastructural features and genetic divergence. This integrative approach highlights the value of combining high-resolution sequence data with detailed morphology to resolve complex parasite groups and to refine their systematic placement within Platyhelminthes.

Molecular Phylogenetics of Fish Parasites publication trend

The graph below shows the total number of articles in molecular phylogenetics of fish parasites across all publications each year (not limited to Nature Index journals).

Technical terms

Molecular phylogenetics: The study of evolutionary relationships among organisms using molecular sequence data, typically by reconstructing phylogenetic trees.

28S ribosomal RNA gene: A component of the large subunit of ribosomes, commonly used as a marker for deep-level phylogenetic analyses in eukaryotes due to its conserved and variable regions.

Cytochrome c oxidase I (COI): A mitochondrial gene often employed for species-level discrimination and DNA barcoding, reflecting maternal lineages and rapid evolutionary rates.

Monophyletic group: A set of organisms that includes an ancestor and all its descendants, representing a single branch on the tree of life.

Polytomy: A node in a phylogenetic tree where more than two lineages emerge, indicating unresolved relationships often due to rapid radiation or insufficient data.

References

1. Characterisation of Temnocephalidae flatworms in common Australian freshwater prawn, Macrobrachium australiense. Scientific Reports (2022).
2. A large 28S rDNA-based phylogeny confirms the limitations of established morphological characters for classification of proteocephalidean tapeworms (Platyhelminthes, Cestoda). ZooKeys (2015).
3. Revision of Gangesia (Cestoda: Proteocephalidea) in the Indomalayan Region: Morphology, Molecules and Surface Ultrastructure. PLOS ONE (2012).
4. Parasitological and molecular identification of cestode Bothriocephalus scorpii sensu stricto in the new host Chelidonichthys lucerna (L. 1758) (Triglidae, Scorpaenoidei) from the North Sea. The European Zoological Journal (2023).