A regional scale study of parasites in Percichthys trucha, an endemic fish of southern South America: insights on diversity and distribution from two decades of field surveys

Abstract

The current conservation status of Percichthys trucha (Creole perch) is Least Concern, although the population trend isconsidered to be decreasing. We conducted an extensive survey of parasite fauna in this species over two decades in its dis-tribution range in Argentina. Fish were collected using gill and trawl nets. Parasites were collected, identified, and countedto calculate prevalence and mean intensity. The present work reports the parasite species infecting P. trucha, using data fromour own survey and from previously published records. This information enables us to evaluate infection and distributionpatterns, assess the role of P. trucha as host, determine the specificity of the parasites, and evaluate the threat representedby introduced, invasive parasites. The data set consists of a total of 453 host-parasite-locality records, of which only 15 areexclusively bibliographic. We found 44 parasite taxa: 19 digeneans, 4 monogeneans, 5 cestodes, 8 nematodes, 4 acantho-cephalans, 3 crustaceans, and 1 mollusk. The most represented families were Diplostomidae, Heterophyidae, and Dactylogy-ridae. This study increases the number of parasite species known from 25 to 44. It can be concluded that this parasite faunais characterized by high diversity, particularly of digeneans, and most of the parasites reproduce within this host, a patternwhich is related to the top position of this fish species in the trophic webs. Six parasite species (Allocreadium patagonicum,Homalometron papilliferum, Acanthostomoides apophalliformis, Duplaccessorius andinus, Pseudodelphys limnicola, andHysterothylacium patagonense) exhibit high host specificity (only matures in Creole perches) and are widely distributed,which could now be considered as “biogeographical core helminth fauna.” Some P. trucha populations are affected by theinvasion of alien fishes like Cyprinus carpio and pathogenic parasites like Lernaea cyprinacea and Schizocotyle acheilog-nathi. Our findings emphasize the need for further research.