Salsuginus seculus (Monogenea: Ancyrocephalidae) and Gyrodactylus gambusiae (Monogenea: Gyrodactylidae) newly recorded infesting Gambusia affinis (Teleostei: Poeciliidae) from New Zealand

The North American western mosquitofish, Gambusia affinis (Baird and Girard, 1853), has been introduced into a number of countries around the world, primarily for the control of mosquito populations. Gambusia affinis is known to harbour several monogenean parasites, which have the potential to be co-introduced to new regions. However, despite the broad non-native distribution of this fish species, their monogenean parasites have been reported from a relatively small number of locations. Parasitological investigations have identified very few freshwater monogenean parasites from freshwater fish in New Zealand. Two monogenean parasites were recorded infesting G. affinis in New Zealand; Salsuginus seculus (Mizelle and Arcadi, 1945) (a new genus to New Zealand) on the gills and Gyrodactlyus gambusiae Rogers and Welborn, 1965, on the gills and surface of the fish. Despite the broad distribution of G. affinis, S. seculus and G. gambusiae have been reported in few countries due, perhaps, to lack of research effort on monogeneans, their small size, enemy-release, or a combination of these factors. Based on the diversity of monogeneans in other countries that are found associated with fish with non-native populations in New Zealand, it is likely that many unrecognised non-native monogeneans are established in New Zealand's freshwater ecosystems alongside their fish hosts. Further, the number of introduced monogeneans is likely to be even higher than is currently appreciated when considering non-native fish in the aquarium trade and other introduced freshwater fauna, such as terrapins.