First evidence for a possible invasional meltdown among invasive fish parasites

Abstract

Biological invasions are frequently studied topics in ecological research. Unfortunately, within invasion ecology parasite-associated aspects such as parasite impacts on new environments and on local host populations are less well-studied. Round gobies migrating from the Ponto-Caspian region into the Rhine River system are heavily infested with the Ponto-Caspian acanthocephalan parasite Pomphorhynchus laevis. As shown by experimental infestations the acanthocephalans occur as pre-adults in host-encapsulated cysts within the internal organs of the migrating gobies, but remain infective for their definitive host chub. Recently, we described the occurrence of larvae of another parasite, the invasive eel swim bladder nematode Anguillicola crassus, in these Pomphorhynchus cysts. In the present study, we could prove the infectivity of the nematode larvae for European eels for the first time. After experimental inoculation of Pomphorhynchus cysts occasionally infested with A. crassus larvae, the nematodes grow to maturity and reproduce whereas all P. laevis were unviable. We therefore postulate that the nematode larvae behave like immunological hitchhikers that follow a “Trojan horse strategy” in order to avoid the paratenic host’s immune response. Accordingly, the interaction between both invasive parasites gives first evidence that the invasional meltdown hypothesis may also apply to parasites.

The Ecological Importance of Amphipod–Parasite Associations for Aquatic Ecosystems

“…Invasion by exotic species is another phenomenon capable of profoundly altering both host-parasite interactions and ecosystems. Introduced animals may (i) bring their parasites and transfer them to native hosts (spill-over), intensifying the negative impact on native host populations and changing their parasite communities; (ii) lose all or most of their parasites (enemy release) and obtain an advantage over native species; and (iii) acquire local native parasites and induce a spillback or a dilution effect on native hosts [50,[72][73][74][75][76]. In all the aforementioned scenarios, parasites may affect or even drive the invasion dynamics with repercussions on host and non-host species, and biodiversity in general [77][78][79].…”

Experimental evidence of invasion facilitation in the zebra mussel-killer shrimp system

“…The preference for zebra mussel beds shown by the killer shrimp (at least when they are tested in groups), and the fact that they are strongly attracted to the zebra mussel scent, suggests this could be an example of invasion facilitation, as seen in other studies. For example, positive synergies resulting in invasion facilitation have been reported for an invasive algae and an invasive bryozoan (Levin et al 2002), as well as among invasive fish parasites (Hohenadler et al 2018). Other well known examples of invasion facilitation, include the bullfrog-sunfish system, where the survival of the invasive bullfrog ( Rana catesbeiana ) was enhanced by the presence of the non native bluegill sunfish ( Lepomis macrochirus ) because the latter preyed on native L dragonfly which in turn preyed on bullfrog tadpoles (Adams et al 2003).…”

Peer Review #1 of "Experimental evidence of chemical attraction in the mutualistic zebra mussel-killer shrimp system (v0.1)"

“…Manuscript to be reviewed scent, suggests that this could be an example of invasion facilitation, as seen in other studies. For example, positive synergies resulting in invasion facilitation have been reported for an invasive algae and an invasive bryozoan (Levin et al 2002), as well as among invasive fish parasites (Hohenadler et al 2018). Other well known examples of invasion facilitation, include the bullfrog-sunfish system, where the survival of the invasive bullfrog (Rana catesbeiana) was enhanced by the presence of the non-native bluegill sunfish (Lepomis macrochirus) because the latter preyed on native dragonfly which in turn preyed on bullfrog tadpoles (Adams et al 2003).…”