Abstract
Translocation of fishes for aquaculture has resulted in the co-introduction of some of their parasites. African cichlid fishes, generically called “tilapias” have been introduced worldwide, along with their monogenean parasites. In a nation-wide survey, we characterised monogeneans of the genus Gyrodactylus infecting farmed “tilapia” throughout Mexico. We also collected native fishes around farms, to look for potential parasite spillover from cultured fishes. Monogeneans were identified taxonomically using morphological and molecular characters. Originally African, pathogenic Gyrodactylus cichlidarum was recorded in every farm surveyed, infecting different “tilapia” varieties, as well as three native cichlid fish species. Previously, we had shown that G. cichlidarum also infects native, non-cichlid fishes in Mexico. We also recorded that Gyrodactylus yacatli is widely distributed in Mexico, infecting cultured “tilapia” and native fishes; and present data indicating that this is a further translocated African parasite. A third, unidentified gyrodactylid infected farmed and native fishes in Chiapas, southern Mexico; we describe the new species as Gyrodactylus shinni n. sp., and provide evidence that this is a third monogenean translocated with African fish. The wide distribution of exotic parasites co-introduced with “tilapia” and their spillover to native fishes may have an important impact on the ichthyofauna in Mexico, one the world’s megadiverse countries.
Highlights
Among teleost fishes, the family Cichlidae possesses one of the highest species richness (> 1700 known species), including at least 900 freshwater African species[1]
In Mexico, the first recorded introduction of “tilapias” dates from 1945, when redbelly tilapia Coptodon zillii was imported from the USA; while in 1964, Nile tilapia was introduced from “Africa” and Costa Rica, and both blue tilapia O. aureus and Mozambique tilapia O. mossambicus were introduced from the USA; redbreast tilapia C. rendalli was imported from Cuba in 1968; and Wami tilapia O. urolepis was translocated from Costa Rica in 19788
The intra-specific variation of 24 isolates of G. yacatli ranged from 0.1 to 3.2%. This survey provides evidence that three African gyrodactylid parasites translocated into Mexico with their “tilapia” hosts are widely distributed in fish farms throughout the country; and have spilled-over to native cichlids
Summary
The family Cichlidae possesses one of the highest species richness (> 1700 known species), including at least 900 freshwater African species[1]. Gyrodactylus yacatli was previously recorded to infect “tilapia” in southeastern Mexico[7], and O. niloticus and the cichlid Pseudocrenilabrus philander in Zimbabwe[18]; but the low prevalence of this species both in Mexico and Zimbabwe, and the unavailability of molecular data for African samples precluded support for any hypothesis on the biogeographical origin of the taxon. The main objectives of this survey were (1) to explore the presence and distribution of the known Gyrodactylus species infecting cultured “tilapia” throughout Mexico; (2) to assess the potential spillover of parasites to native fish species in the vicinity of aquaculture facilities, and look for evidence of host switches from native cichlids to farmed “tilapia”; (3) to better understand the likely biogeographical origin of G. yacatli; and (4) to generate morphological and molecular data to explore variation within gyrodactylids infecting “tilapia” throughout Mexico; and, if present, characterize new taxa
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