Exotic species typically lose most of their associated parasites during long-distance spread. However, the few parasites that are co-introduced may have considerable adverse impacts on their novel hosts, including mass mortalities. We present a comprehensive inventory of parasites known to infect 38 species of exotic invertebrates established in the Great Lakes, as well as 16 invertebrate species predicted to arrive in the near future, all of them crustaceans. Based on a literature analysis, we identified a total of 277 parasite taxa associated with the examined invertebrates in their native ranges and/or invaded areas. Of these parasites, 56 species have been documented to cause various pathologies in their intermediate or final hosts, with humans and fishes being the most frequently affected host categories. Potentially harmful parasites were identified in 61% of the invaders for which published information was retrieved (in their ranges outside of the Great Lakes), with molluscs and crustaceans hosting the highest numbers of such parasites. The results of our study provide a baseline for further assessment and management of the parasitological risks posed by exotic species to the Great Lakes.
Human and Ecological Risk Assessment (2013) DOI: 10.1080/10807039.2013.774576 (Online First)

One of the most significant ecological and economic impacts of exotic species is associated with their role as vectors for the introduction of parasites into invaded areas. Exotic parasites may have devastating impacts on invaded ecosystems; moreover, invaders may also become hosts for aboriginal parasites, promoting native diseases that otherwise would not have emerged. During 2009 and 2010, exotic molluscs were collected from 27 sites in the Lower Great Lakes and their tributaries, the Finger Lakes, and Lake Oneida. Seven species of exotic molluscs were examined for the presence of trematodes, including the zebra mussel (Dreissena polymorpha), quagga mussel (Dreissena rostriformis bugensis), faucet snail (Bithynla tentaculata), European stream valvata (Valvata piscinalis), Asian clam (Corbicula fluminea), Chinese mystery snail (Cipangopaludina chinensis), and the New Zealand mudsnail (Potamopyrgus antipodarum). Most of the examined molluscs were infected with trematode larvae that may be harmful to their subsequent vertebrate hosts, including fish, birds, and mammals. These included Sphaeridiotrema sp. cercariae and Cyathocotyle bushiensis metacercariae from B. tentaculata, Echinostoma sp. cercariae from V. piscinalis, and echinostomatid metacercariae from Dreissena spp. and C. fluminea. Many exotic molluscs that were believed to be free of parasites have already acquired trematodes native to North America. Hotspots of trematode infections were recorded in the western basin of Lake Erie and in Lake Oneida, where several species of exotic molluscs had a high prevalence of trematodes, and thus potentially pose risk of transmission to definitive hosts.
Journal of Shellfish Research (2012) 31(3): 885-894

The zebra mussel (Dreissena polymorpha) and its congener the quagga mussel (Dreissena rostriformis bugensis) are both invaders in freshwater, but have very different invasion histories, with zebra mussels attaining substantially faster rates of spread at virtually all spatial scales. However, in waterbodies where they co-occur, D. r. bugensis can displace D. polymorpha. To determine if the mechanisms for this displacement are associated with different survival and growth, we kept mussels in flow-through tanks for 289 days with two temperature regimes that mimicked the natural surface water (littoral zone) and hypolimnion conditions of Lake Erie. For the littoral zone regime, we used water directly from the surface of Lake Erie (range 4–25°C, average 11.9 ± 0.6°C). For the profundal zone treatment, Lake Erie surface water was chilled to about 6°C (range 5–8°C, average 6.2 ± 0.6°C) for the full duration of the experiment. For each of these temperature regimes, we used three replicate tanks with only zebra mussels present and three replicate tanks with only quagga mussels (150 ind./tank each), and three replicate tanks with both species (75 ind./tank of each species). Quagga mussels had higher survivorship and grew more than zebra mussels in all treatments. For both species, the size of the mussel entering the winter was critical for survivorship. Larger mussels had a higher survival over the winter in all treatments. For both species, there was a survivorship and growth tradeoff. In the warmer littoral zone treatment both species had higher growth, but lower survival than in the colder profundal zone treatment. Surprisingly, although quagga mussels outperformed zebra mussels, zebra mussel survivorship was better when they were faced with competition by quagga mussels than with just intraspecific competition. In addition, quagga mussels suffered size-specific mortality during the growing season only when facing interspecific competition with zebra mussels. Further experiments are needed to determine the possible mechanisms for these interspecific effects.
Hydrobiologia (2010) 668(1): 183-194