Hot, sour, and spicy: Tolerance of bee and mosquito parasites to temperature, acidity, and phytochemicals reflect host physiology and diet

On-Demand

Presenting Author(s)

Evan C. Palmer-Young

Research Associate
USDA-ARS
Beltsville, Maryland

Co-Author(s)

TR

Thomas Raffel

Associate Professor of Biology
Oakland University
Oakland, Michigan
RS

Ryan Schwarz

Fort Lewis College
Durango, Colorado
YC

Yanping Chen

Research Leader
USDA-ARS
Beltsville, Maryland
JE

Jay Evans

Research Leader
USDA-ARS
Beltsville, Maryland

Heat, acidity, and antimicrobial phytochemicals are three factors that can limit parasitic infection. The colony-level endothermy, acidic guts, and pollen-based diets of social bees provide unique opportunities to study how temperature, acidity, and dietary phytochemicals shape insect-parasite associations. We compared temperature, pH, and phytochemical tolerance between three trypanosomatid gut parasites from social bees and a related trypanosomatid from poikilothermic mosquitoes, which have alkaline guts and pollen-free diets.

Relative to mosquito parasites, bee parasites had higher heat tolerance that reflected body temperatures of hosts. Heat tolerance of the honey bee parasite Crithidia mellificae was exceptional for its genus, implicating honey bee endothermy as a plausible filter of parasite establishment. Whereas both honey bee parasites tolerated the acidic pH's found in bee intestines, mosquito parasites tolerated the alkaline conditions found in mosquito midguts. Bee parasites exhibited greater tolerance of chrysin—a flavonoid found in nectar, pollen, and plant resin-derived propolis. In contrast, mosquito parasites were more tolerant of cinnamic acid—a product of lignin decomposition present in woody debris-rich larval habitats.

Collectively, these results suggest that temperature, gut pH, and ingested phytochemicals could influence the distribution of trypanosomatids in insects and resistance to infection in pollinators.