Capillaria pterophylli Heinze, 1933 (Nematoda: Capillariidae Railliet, 1915) in imported ornamental Cichlidae from Asia into South Africa: the first molecular data and scanning electron microscopy
Capillaria pterophylli Heinze, 1933 is an intestinal parasite of ornamental cichlids, known for its pathogenic impact in aquaria. Despite its veterinary significance and widespread presence in ornamental aquaculture, limited molecular data and phylogenetic information are available for this species. This study aimed to provide an integrative redescription of C. pterophylli based on morphological observations with scanning electron microscopy (SEM) and molecular data, with the determination of epidemiological indices (prevalence and mean intensity). Between September 2022 and November 2023, 414 individuals of 18 ornamental cichlid species were sampled from shipments originating in Indonesia, Sri Lanka, and Thailand. Fish specimens were dissected to screen for gastrointestinal nematodes. Morphological identification was carried out using standard light microscopy and SEM. Molecular analyses targeted the 18SrDNA gene, followed by phylogenetic inference using maximum likelihood, Bayesian inference, and neighbour-joining approaches. Capillaria pterophylli was confirmed in three species: Andinoacara pulcher (Gill, 1858), Pterophyllum scalare (Schultze, 1823), and Uaru amphiacanthoides Heckel, 1840. The highest prevalence and mean intensity were recorded in P. scalare from Indonesia (52.94%, MI = 18.7). SEM revealed diagnostic features such as a rounded anterior end, barrel-shaped eggs with fine surface sculpturing, and a subterminal anal pore. Phylogenetic analysis based on the 18S rDNA region confirmed the placement of C. pterophylli as a sister taxon to other Capillaria species parasitising avian hosts, suggesting a complex evolutionary history. This study expands the known host range of C. pterophylli by reporting two new host records. The findings highlight the pervasive risk of pathogen introduction via the ornamental fish trade and underscore the critical need for integrating molecular tools into biosecurity and surveillance protocols to mitigate future transboundary spread.