Rothchild, Kristina W., Adler, Lynn S., Irwin, Rebecca E., Sadd, Ben M., Stevenson, Philip C. ORCID: https://orcid.org/0000-0002-0736-3619 and Palmer-Young, Evan C. (2018) Effects of short-term exposure to naturally occurring thymol concentrations on transmission of a bumble bee parasite. Ecological Entomology, 43 (5). pp. 567-577. ISSN 0307-6946 (Print), 1365-2311 (Online) (doi:10.1111/een.12631)

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Abstract

Background:
Plants produce antimicrobial phytochemicals that can reduce growth and infectivity of parasites in animals. Pollinator parasites are transmitted between hosts that forage on shared flowers. Floral transmission directly exposes parasites to phytochemicals on floral surfaces and in nectar, both at flowers and, post-ingestion, in the crop. This exposure could directly affect parasite transmission to new hosts.

Approach:
We combined nectar chemical analyses with field and cell culture experiments to test effects of the floral phytochemical thymol on transmission potential of the trypanosomatid gut parasite Crithidia in Bombus impatiens. First, we measured thymol concentrations in Thymus vulgaris nectar. Second, we tested how addition of thymol to floral nectaries affected parasite transmission to foraging bees. Third, we used cell cultures to determine direct, dose-dependent effects of short term thymol exposure on subsequent in vitro parasite growth.

Results:
We found 26.1 ppm thymol in Thymus vulgaris nectar, 5-fold higher than previously documented in this species. However, addition of thymol to flowers of parasite-inoculated inflorescences of four plant species did not affect acquisition of Crithidia infection during a foraging bout. Cell culture experiments showed that thymol concentrations needed to reduce subsequent Crithidia growth by 50% (120 ppm) were 4.6-fold higher than the highest detected nectar concentration.

Conclusions:
Although thymol exposure can influence Crithidia viability, Crithidia are robust to the duration and magnitude of exposure encountered during floral foraging under natural conditions. Our experiments suggest that any effects of thymol alone on Crithidia-host infection dynamics probably reflect indirect, possibly host-mediated, effects of chronic thymol ingestion.

Item Type:	Article
Uncontrolled Keywords:	tritrophic interactions, plant secondary metabolites, terpenoids, trypanosomatids, horizontal transmission, floral trait manipulation
Subjects:	S Agriculture > S Agriculture (General)
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > Natural Resources Institute Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment Department Faculty of Engineering & Science > Natural Resources Institute > Chemical Ecology Research Group
Last Modified:	12 May 2019 01:38
URI:	http://gala.gre.ac.uk/id/eprint/19741

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