The distribution and effects of microbeads on host-parasite interactions of Ontario wetland fauna: tadpoles, snails and trematodes

Plastic microbeads pose an environmental problem as they easily enter into waterbodies, take a long time to break down, and their ingestion can have negative effects on aquatic organisms. I found that microbead consumption had a significant negative effect on the growth of northern leopard frog (Lithobates pipiens) tadpoles, as well as their susceptibility to trematode parasite (Echinostoma trivolvis) infection, but minimal effects on leukocyte profiles and infection tolerance. Freshwater snails (Stagnicola elodes) given microbead diets exhibited a non-monotonic response in their production of trematode (Haematolechus parviplexus) infectious stages, with those in the highest microbead treatment tending to exhibit greater growth and shorter longevity. I also found that algae (Chlorella pyrenoidosa) and microbeads created density-dependent aggregations that could be a potential ingestion pathway for herbivorous fauna. Lastly, I found many particles in Ontario wetlands and ponds that may be used for controlled pesticide release, thus potentially posing a threat.

The distribution and effects of microbeads on host-parasite interactions of Ontario wetland fauna: tadpoles, snails and trematodes

Plastic microbeads pose an environmental problem as they easily enter into waterbodies, take a long time to break down, and their ingestion can have negative effects on aquatic organisms. I found that microbead consumption had a significant negative effect on the growth of northern leopard frog (Lithobates pipiens) tadpoles, as well as their susceptibility to trematode parasite (Echinostoma trivolvis) infection, but minimal effects on leukocyte profiles and infection tolerance. Freshwater snails (Stagnicola elodes) given microbead diets exhibited a non-monotonic response in their production of trematode (Haematolechus parviplexus) infectious stages, with those in the highest microbead treatment tending to exhibit greater growth and shorter longevity. I also found that algae (Chlorella pyrenoidosa) and microbeads created density-dependent aggregations that could be a potential ingestion pathway for herbivorous fauna. Lastly, I found many particles in Ontario wetlands and ponds that may be used for controlled pesticide release, thus potentially posing a threat.

Timing and order of exposure to two echinostome species affect patterns of infection in larval amphibians

The study of priority effects with respect to coinfections is still in its infancy. Moreover, existing coinfection studies typically focus on infection outcomes associated with exposure to distinct sets of parasite species, despite that functionally and morphologically similar parasite species commonly coexist in nature. Therefore, it is important to understand how interactions between similar parasites influence infection outcomes. Surveys at seven ponds in northwest Pennsylvania found that multiple species of echinostomes commonly co-occur. Using a larval anuran host (Rana pipiens) and the two most commonly identified echinostome species from our field surveys (Echinostoma trivolvis and Echinoparyphium lineage 3), we examined how species composition and timing of exposure affect patterns of infection. When tadpoles were exposed to both parasites simultaneously, infection loads were higher than when exposed to Echinoparyphium alone but similar to being exposed to Echinostoma alone. When tadpoles were sequentially exposed to the parasite species, tadpoles first exposed to Echinoparyphium had 23% lower infection loads than tadpoles first exposed to Echinostoma. These findings demonstrate that exposure timing and order, even with similar parasites, can influence coinfection outcomes, and emphasize the importance of using molecular methods to identify parasites for ecological studies.

Checklist of the parasites of the black-necked swan, Cygnus melanocoryphus (Aves: Anatidae), with new records from Chile

Black-necked swans (Cygnus melanocoryphus) are endemic to the southern cone of South America. Their range extends from Brazil and Paraguay south to Argentina and Chile. A total of 16 parasite species were collected from 7 swans from the Biobio region, Chile, of which 12 are new records for Chile and 11 represent new host records, Echinostoma trivolvis, Paranomostomum sp., Microsomacanthus sp., Nadejdolepis sp., Retinometra sp., Avioserpens sp., Capillaria skrjabini, Ingrassia cygni, Anatoecus penicillatus, A. icterodes and A. keymeri. A checklist is presented that summarizes sites of infections, localities, life cycles and their intermediate hosts (if known), and the pertinent references to demonstrate the wide diversity of parasites of black-necked swans. Our review of the existing literature (23 publications) along with our own records provided information on a total of 18 families and 27 genera, including 33 described species (some only identified to genus), of which 11 were recorded only in Chile (8 endoparasites and 3 ectoparasites), and 6 only in Argentina (4 endoparasites and 2 ectoparasites). Five parasites are known only from captive swans in European zoos. Parasites recorded from C. melanocoryphus include 23 helminths and 10 ectoparasites (one leech and 9 arthropods).