Combining laboratory and field approaches to investigate the importance of flower nectar in the horizontal transmission of a bumblebee parasite
2014
Cisarovsky, Gabriel | Schmid‐Hempel, Paul
Knowledge of the complete life cycle of a parasite is crucial to understand the epidemiology and population dynamics of a disease. The populations of several social insect pollinators are decreasing, and parasites are often cited as a contributing factor. The exact transmission pathway of the bumblebee parasite Crithidia bombi (Lipa & Triggiani) (Kinetoplastea: Trypanosomatidae) between two hosts is still unknown, although a previous laboratory experiment suggests transmission via the nectar of flowers. Plant species may differentially protect or negatively affect the parasite while it resides in the flower, for instance if plants vary in their floral shape or the compounds present in their nectar. This will lead to differential transmission success and potentially influence disease epidemiology. In the present study we aimed at determining whether the parasite may indeed be transmitted in the nectar by the bumblebee Bombus terrestris (L.) (Hymenoptera: Apidae). We found that parasite survival was significantly decreased in water with higher sugar concentrations. However, none of the field‐collected nectar samples contained parasite cells, and no parasite cells were transmitted between two artificial flowers by a foraging worker under laboratory conditions. Our results suggest instead that parasite cells may be deposited on flower surfaces and transported on worker surfaces.
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