Molecular and morphological confirmation of an invasive American isopod; Livoneca redmanii Leach, 1818, from the Mediterranean region to Lake Qaroun, Egypt

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Abstract

In 2015, unknown cymothoid isopod parasites were found in Lake Qaroun, a high-salinity closed inland lake in north-central Egypt, which were linked to substantial fish mortalities. The parasites infected a wide range of commercially important fish hosts, including Redbelly tilapia, Tilapia zillii, European Seabass , Dicentrarchus labrax, Common Sole, Solea solea, and mullets Mugil spp. and Liza spp., and continue to present a threat to local fisheries. A number of recent publications (in aggregate) have suggested this introduction reflected a near simultaneous introduction of up to four cymothoid species in Lake Qaroun; however, many of the provided photographs and illustrations were incorrect at the generic and species level. Cymothoid isopod samples were collected from Shakshouk village on Lake Qaroun. An integrative taxonomic approach was applied in the current study, incorporating traditional taxonomic analysis and DNA barcoding through mitochondrial COI gene sequencing, as well as genetic phylogenies to delimit isopods collected in Lake Qaroun. All isopods examined were identified as Livoneca redmanii Leach, 1818, an estuarine-marine species native to the western Atlantic. These samples were genetically and phylogenetically identical to their counterparts collected from Chesapeake Bay in the East of the USA. This species was characterized by pigmentation on cephalon, pereonites, pleonites, telson, pereopods and slightly bent to the left. A review of the recent literature of cymothoids in Lake Qaroun and adjacent marine areas concluded that the majority of individuals identified as species other than L. redmanii were actually L. redmanii, or unidentifiable juvenile cymothoids, with the exception of a juvenile Anilocra sp.. Likewise, L. redmanii is also present in eastern Mediterranean and Suez Canal. The likely introduced vector into Lake Qaroun are fish stockings originating from the Mediterranean Sea and River Nile estuary (as is surmised with the introduced American ctenophore species, Mnemiopsis leidyi). This information can help fishery managers better understand parasite-host dynamics in Lake Qaroun and develop biocontrol strategies to mitigate its impact in Lake Qaroun and limit its spread among adjacent lacustrine, estuarine and coastal systems.

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