Submitted to: Comparative Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2011
Publication Date: 7/4/2012
Citation: Wagner, B.A., Hoberg, E.P., Somers, C.M., Soos, C., Fenton, H., Jenkins, E.J. 2012. Gastrointestinal Helminth Parasites of Double-Crested Cormorants (Phalacrocorax auritus) at Four Sites in Saskatchewan, Canada, 2006-2007. Comparative Parasitology. 79:275-282. Interpretive Summary: Parasites are powerful indicators of ecological structure and interactions, particularly those involving foraging behavior and food habits. Identification of such linkages is dependant on the development of baseline data for distribution and host associations by various parasites on local to regional scales. As a cumulative process, such survey and inventory for faunal structure provides the foundations to explore ecological change and perturbations associated with climate and other forces. We provide the first data for parasite diversity in adult double-crested cormorants from breeding colonies on four very different lakes spanning a major ecotone (borderland between ecological zones) from prairie to boreal forest in Saskatchewan, Canada. We documented regional parasite faunas, and identified potential differences in the occurrence of helminths based on breeding colony location. Eight species of helminths, including putative new species of a tapeworm and a nematode were identified. Contrary to expectations, the overall parasite fauna did not differ substantially across the habitats that were assessed. Circulation of all parasites appears associated with a diet dominated by fishes. We established that parasite abundance (numbers) and diversity (number of species) may be useful indicators of differences in feeding ecology. A baseline is established against which to assess future changes in these aquatic systems in a regime of accelerated climate change. A basis is also provided for assessing the role of some birds in the dissemination and maintenance of parasites of potential significance to food production and aquaculture. Results of this research will be of benefit to wildlife parasitologists and those involved in aquaculture where avian parasites may infect fish.
Technical Abstract: We examined the gastrointestinal parasite fauna of adult double-crested cormorants from breeding colonies on four very different lakes spanning a major ecotone from prairie to boreal forest in Saskatchewan, Canada. Our objectives were to document regional parasite fauna, and identify potential differences based on breeding colony location. Eight species of helminths were identified from the stomach and small intestinal contents of 92 cormorants collected during the summers of 2006 and 2007: 2 nematodes- Syncuaria squamata and Contracaecum cf. rudolphii; 2 trematodes - Ribeiroia ondatrae and Drepanocephalus spathans; and 4 cestodes- Ligula colymbi, Schistocephalus solidus, Paradilepis caballeroi, Paradilepis sp. nov.) Our results include an apparently undescribed species of Paradilepis, new host records for L. colymbi, S. solidus, and R. ondatrae, and new geographic records for S. squamata, D. spathans, and P. caballeroi in cormorants of western Canada. Anisakids, C. rudolphii, were present in total stomach contents of all but one cormorant, and were variably associated with mucosal ulceration and hemorrhage. Cryptic diversity within this genus suggests that this may represent a previously undescribed species. The occurrence of an acanthocephalan, Pomphorhynchus bulbocolli, and plerocercoids of the cestode Diphyllobothrium are considered to be artifacts of a piscivorous diet. Overall parasite fauna did not differ predictably by location; however, birds at a breeding colony that consumed a high proportion of amphibians (instead of fish) had decreased prevalence and intensity of D. spathans. Parasite abundance and diversity may be a useful indicator of differences in feeding ecology among wildlife populations.