Feral parasites: African monogeneans recorded in ferine Nile tilapia in Oaxaca, Mexico

Abstract

Monogenean parasites associated to cultured Nile tilapia Oreochromis niloticus have been co-introduced globally. In this survey, we assessed how prevalent these ectoparasites are in both rustic fish farms in Oaxaca, Mexico and in feral tilapia in the vicinity of these farms. We provide molecular data (D2 + D3 domains of the large subunit of the 28S rDNA gene and the Internal Transcribed Spacers, ITS1 + 5.8S + ITS2 rDNA) to confirm the taxonomic identity of the parasites and —eventually— to trace their anthropogenic introductions and assess their ecological impact. We demonstrate that four African monogeneans infect farmed and feral tilapia in Oaxaca. The dactylogyrids Cichlidogyrus sclerosus and C. tilapiae were recorded on farmed tilapia, and C. sclerosus on feral fish in the vicinity of farms. The gyrodactylids Gyrodactylus cichlidarum and G. yacatli infected feral tilapia, both near and further away from farms. The present survey suggests that the deficient biosafety protocols in rustic tilapia farms enable parasites to escape from fish farms and potentially spill-over to native fishes. Considering monogeneans associated to tilapia are known pathogens and very successful invaders, an effort should be made to assess their impact on native fishes — particularly in very biodiverse regions, like Oaxaca.