The reciprocal influence of trematode parasites and malathion on developing pickerel frogs (Rana palustris)

To examine the interactions of disease and pollution on amphibian populations around the world, I investigated the effect of infection on contaminant susceptibility in pickerel frog, Rana palustris, larvae. I conducted standard 48-hr toxicity tests to examine effect of trematode parasite, Echinostoma trivolvis, infection (0, 10, or 30 cercaria) on the susceptibility of pickerel frog tadpoles to the widely used organophosphate insecticide malathion. LC50 values ranged from 16.5 – 17.4 mg/L, within the range reported for other amphibian species. I found no differences in susceptibility to malathion among parasite treatments. Nevertheless, this crucial question remains to be tested in other amphibian host-parasite systems. Second, I studied the reverse interaction, the effect of pesticide exposure on susceptibility to parasite infection. I exposed pickerel frog embryos to low doses of malathion, then subjected morphologically normal tadpoles to E. trivolvis later in development. Malathion significantly decreased hatching success and viability rates at concentrations lower than previously documented for anuran embryos. After 7 wk of development in water with no malathion, tadpoles previously exposed to malathion as embryos suffered increased parasite encystment rates compared to controls. My research identifies embryonic development as a sensitive window and the potential for increased susceptibility to infection long after pesticide exposure has ceased. With potential for increased parasite prevalence from eutrophication and climate change, my data underscore the importance of understanding the reciprocal influences of parasites and pesticides in amphibians.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Fisheries and Wildlife Sciences

Department dc:contributor.department

Fisheries and Wildlife Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2007

Author dc:creator

• Budischak, Sarah Ashcom

Chair dc:contributor.committeechair

• Hopkins, William A.

Committee members dc:contributor.committeemember

• Belden, Lisa K.
• Neves, Richard J.

• sublethal
• latent
• trematode
• acetylcholinesterase
• malathion

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-10302007-123149

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/35534