Diversity of fish parasites in a South Carolina estuary - interesting infection patterns and taxonomic hurdles

Abstract

In April and May of 2023, sampling of fish parasite fauna was conducted in the Stono River estuary, in South Carolina, USA. The sampling and the following research of collected parasites were done as part of a BioBlitz, which is a project with an aim of recording all living species within a chosen area, such as urban park or nature reserve. In this case, Stono River estuary is protected as a Stono Preserve area because of its history and the biodiversity present. In this study, 125 fish specimens of 12 genera (17 species) were caught and inspected for parasites; members of only six genera (nine species) were infected: Anchoa (A. mitchilli), Fundulus (F. confluentus, F. heteroclitus, F. majalis), Gambusia (G. holbrooki), Gobiosoma (G. bosc), Menidia (Menidia sp.) and Mugil (M. cephalus, M. curema). From these hosts, 130 parasites were collected, and identified based on their morphology and genetic markers (sequences of 28S, 18S and ITS rDNA). The 15 species observed belonged to different lineages of monopisthocotylan flatworms (Fundulotrema, Gyrodactylus, Ligophorus, Salsuginus), polyopisthocotylan flatworms (Metamicrocotyla) and copepods (Bomolochus, Caligus, Ergasilus, Naobranchia). From all screened hosts, species of Ligophorus have the highest mean intensity and prevalence, and Fundulotrema the lowest. Furthermore, M. cephalus harbors the highest parasite species richness (seven), and Anchoa mitchilli and Menidia sp. the lowest (one per each species). Some of the parasites identified present new records for the Atlantic coast of the USA. Sampled parasites show strong patterns of host-specificity and can be found in different habitats within the estuary, such as creeks, small lakes and water reservoirs. This study points to striking lack of molecular data available for North American fish parasites. Greater knowledge of fish parasite diversity in estuaries would help in understanding how parasite diversity is influenced by changing abiotic factors and global climate change.