Pomphorhynchus laevis: An invasive species in the river Rhine?

Morphological and molecular data show no evidence of the proposed replacement of endemic Pomphorhynchus tereticollis by invasive P. laevis in salmonids in southern Germany

“…The framework of the study is an ongoing invasion of a Ponto-Caspian lineage of the acanthocephalan parasite Pomphorhynchus laevis in the Rhine and Danube [15,18]. It was hypothesized that this invasive lineage might migrate (via one of its intermediate or final hosts) further upstream in rhithral rivers in the Rhine and Danube areas, and thereby replaces the endemic Pomphorhynchus species which would alter existing parasite-host relationships.…”

“…Most parasites that were collected in the study area showed bold hooks in middle rows on the proboscis and a characteristic projection on the top of the lower hooks on the proboscis. As these characteristics have been consistently attributed to specimens of P. tereticollis [4,15,26] most individuals were initially classified as this species. However, a recent study of Reier et al [16] using both molecular and morphological methods, showed that Pomphorhynchus specimens captured in the Austrian part of the Danube with morphological characteristics of the proboscis that would classify them as P. tereticollis, had gene sequences (COI) that placed them closely related to P. laevis.…”

“…Most studies on Pomphorhynchus species [4,15,18,19,26,27] have been carried out in larger lowland summer warm (potamal) rivers which are rich in fish species and dominated by cyprinid species. In these rivers both P. laevis and P. tereticollis can be found in a wide range of fish hosts in Central (including the Rhine) and in Ponto-Caspian (including the Danube) Europe [15,18,19,26], with cyprinid species like chub (Squalius cephalus) and barbel (Barbus barbus) as the most common hosts [19]. Here samples were taken from the more elevated, summercold and fast-flowing rhithral tributaries of the Danube and Rhine where salmonids are often the most abundant species.…”

“…They require an arthropod intermediary host, and a vertebrate final host to which they may accrue considerable damage to the intestines [13,14]. Recent literature on Western-European acanthocephalans of the genus Pomphorhynchus has shown the importance of complementing morphological with molecular bar-coding methods in order to study recent changes in species distributions [4,[15][16][17]. The current data suggests that Ponto-Caspian lineages of Pomphorhynchus laevis spread via the Danube-Main-Rhine canal into Western-Europe [18], and are effectively replacing Pomphorhynchus tereticollis populations in the Rhine [15].…”

“…Recent literature on Western-European acanthocephalans of the genus Pomphorhynchus has shown the importance of complementing morphological with molecular bar-coding methods in order to study recent changes in species distributions [4,[15][16][17]. The current data suggests that Ponto-Caspian lineages of Pomphorhynchus laevis spread via the Danube-Main-Rhine canal into Western-Europe [18], and are effectively replacing Pomphorhynchus tereticollis populations in the Rhine [15]. Such a replacement could result in increased mortality of final host species as was shown for A. crassus [6].…”