Diverse Parasite Fauna Research Articles

Haematozoan Parasites and Migratory Behaviour in Waterfowl

Although it has been suggested that migratory species are exposed to a more diverse parasite community than sedentary species, this has not previously been demonstrated. To test this hypothesis, we analysed the diversity and prevalence of infections by haematozoan parasites re- ported in anseriform species (ducks, geese and swans) in relation to host migration patterns. Whilst controlling for research eAort, the number of parasite species or genera reported per host was positively related to migration distance, but not to breeding latitude or size of the breeding or total annual range. In species undergoing longer distance migrations, a higher proportion of individuals were infected by haematozoa. Thus, there is indeed evidence that migratory birds are more sus- ceptible or are exposed to a more diverse parasite fauna and higher risk of infection. This may help to explain why migratory species tend to have more exaggerated, sexually selected traits as well as larger immune system organs.

Host immune defence and migration in birds

Migratory birds are exposed to at least two different parasite faunas during their annual cycle, while resident birds only experience a single parasite fauna. Migratory birds should therefore have evolved mechanisms to control or reduce the negative impact of infections from a more diverse parasite fauna. In a comparison of pairs of closely related species of birds that differ with respect to whether they are migratory or residents, the size of two immune defence organs (the bursa of Fabricius and the spleen) was consistently larger in the migratory species. Since the bursa is only found in juvenile, sexually immature birds, we conclude that immune defence adaptations to the impact of a more diverse parasite fauna in migrants already exist before the start of the first migration. Interspecific differences in investment in immune defence between migratory and resident birds have implications for our understanding of complex host–parasite interactions, the acquisition of new hosts by parasites, and the susceptibility of migratory birds to environmental perturbations.

Parasite recruitment by stocked walleye, Stizostedion vitreum vitreum (Mitchill), fry in a small boreal lake in central Canada.

Six species of parasites were recovered 4 mo after walleye fry were stocked in Heming Lake, Manitoba. The species of parasites acquired most rapidly were those that were non-host-specific and common to the indigenous populations of both walleye and yellow perch (Perca flavescens). Parasite species overlap (Jaccard's indices) was greatest within age groups of walleye and yellow perch, but was also high between older walleye and yellow perch. The higher numbers of parasites recruited by stocked walleye, particularly ones known to induce pathology, raises questions on the success of walleye introductions to aquatic systems with a diverse indigenous parasite fauna and a fish population with a large proportion of yellow perch.

Metazoan parasites of cod, Gadus morhua L., in Canadian Atlantic waters

From July to September 1975, 739+ Atlantic cod, Gadus morhua L., were collected in the Bay of Fundy, Nova Scotia shelf, and southern Gulf of St. Lawrence and were examined for metazoan paraties. Of 49 parasites recorded, 10 were considered more or less specific to cod or related gadid hosts, 9 were considered accidental infections, and the remaining majority of parasites were apparently capable of infecting a wide range of unrelated marine fishes. The general lack of strict host specificity of enteric parasites of northern marine fishes results in a very diverse parasite fauna in fish such as cod which have very broad feeding habits.Metazoan parasites recorded from cod were mostly arctic–boreal transatlantic and amphiboreal species. No species endemic to the northwestern Atlantic were found. However, among all metazoan parasites which are restricted to gadid hosts, there are more endemic species in the North Atlantic, particularly the northwestern Atlantic than present in the North Pacific. This distribution surely reflects the large number of endemic gadid genera and species in the North Atlantic and the probable Atlantic–Arctic origin of the Gadidae.

Parasites of waterfowl, from southwest Texas: III. The green-winged teal, Anas crecca.

Seventy of 72 green-winged teal, Anas crecca, from southwest Texas were infected with parasites. Seventeen species of endoparasites were recorded: Notocotylus attenuatus, Zygocotyle lunata, Typhlocoelum sisowi, Echinostoma revolutum, Hypoderaeum conoideum, Dendritobilharzia pulverulenta, Cloacotaenia megalops, Sobolevicanthus gracilis, Sobolevicanthus krabbeella, Gastrotaenia cygni, Amidostomum acutum, Amidostomum anseris, Tetrameres crami, Echinuria uncinata, Corynosoma constrictum, Polymorphus minutus. Also recorded were five species of ectoparasites: Trinoton querquedulae, Anaticola crassicornis, Anatoecous icterodes, Holomenopon setigerum and Epidermoptes sp. and the sacrosporidian, Sarcocystis rileyi. Anatoecous icterodes is a new host record for A. crecca. Sobolevicanthus gracilis, S. krabbeella, T. sisowi, and D. pulverulenta are new records for A. crecca in North America. Sobolevicanthus krabbeella is also a new record for North America. Fall juveniles had greater mean parasite intensity (29) than fall (19) and spring adults (19). Juveniles were infected with fewer species of parasites (17) than adults (20). Simpson's index was very low (0.11) indicating a diverse parasite fauna. Sorenson's index of similarity indicated that the parasite fauna for green-winged teal from southwest Texas was more similar to the shoveler's, Anas clypeata, parasites reported from southwest Texas (55%) than to green-winged teal parasites reported from eastern Canada (41%) and New Brunswick, Canada (21%).