Monogeneans on exotic Indian freshwater fish. 7. Results of a national study on ornamental fishes from 2019–2022

This study reports the results of a nationwide parasitological survey that was conducted from 2019 to 2022 to investigate the potential introduction of monogenean parasites into India via the ornamental fish trade. A total of 619 individual exotic ornamental fish representing 27 teleost species from nine families were collected from the country's major aquaria markets and examined for monogeneans. To identify monogeneans at the species level, we employed a morphometric analysis of sclerotised structures (haptoral and reproductive hard parts), as well as a molecular analysis of nuclear 28S rRNA and ITS2 regions. Indian conditions for importing exotic ornamental fish species require a pre-quarantine certificate, quarantine treatment, and post-quarantine follow-up. Despite these restrictions, 26 monogenean species from 12 known genera were detected and identified in 17 of the 27 fishes examined. Dactylogyrus was represented by a maximum of nine species, followed by Gyrodactylus with five. Cyprinidae was the most parasitised fish family (13 species), followed by Cichlidae (three species) and Helostomatidae, Poeciliidae, and Serrasalmidae (two species each). The majority of co-transported parasite species originated from Asia (65.38%, n = 17), followed by South America (23.07%, n = 6), North and Central America (7.69%, n = 2), and Africa (3.5%, n = 1). Three fish species were identified as the first host records for monogenean parasites: Chindongo socolofi for Cichlidogyrus tilapiae Paperna, 1960, Metynnis hypsauchen for Mymarothecium sp., and Betta splendens for Heteronchocleidus sp. In general, exotic populations had fewer parasite species than in their native distribution ranges.