Eristalis flower flies can be mechanical vectors of the common trypanosome bee parasite, Crithidia bombi

• Published in: Scientific reports Vol. 11; no. 1; pp. 15852 - 10
• Main Authors: Davis, Abby E., Deutsch, Kaitlin R., Torres, Alondra M., Mata Loya, Mesly J., Cody, Lauren V., Harte, Emma, Sossa, David, Muñiz, Paige A., Ng, Wee Hao, McArt, Scott H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04-08-2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/158/853; 631/601/1466; Animals; Crithidia - physiology; Crithidia bombi; Diptera - physiology; Eristalis; Feces; Feces - parasitology; Flowers; Flowers - parasitology; Humanities and Social Sciences; Insect Vectors - parasitology; multidisciplinary; Parasites; Pollination; Pollinators; Science; Science (multidisciplinary); Vectors
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-95323-w

Flowers can be transmission platforms for parasites that impact bee health, yet bees share floral resources with other pollinator taxa, such as flies, that may be hosts or non-host vectors (i.e., mechanical vectors) of parasites. Here, we assessed whether the fecal-orally transmitted gut parasite of bees,
Crithidia bombi
, can infect
Eristalis tenax
flower flies. We also investigated the potential for two confirmed solitary bee hosts of
C. bombi
,
Osmia lignaria
and
Megachile rotundata
, as well as two flower fly species,
Eristalis arbustorum
and
E. tenax,
to transmit the parasite at flowers. We found that
C. bombi
did not replicate (i.e., cause an active infection) in
E. tenax
flies. However, 93% of inoculated flies defecated live
C. bombi
in their first fecal event, and all contaminated fecal events contained
C. bombi
at concentrations sufficient to infect bumble bees. Flies and bees defecated inside the corolla (flower) more frequently than other plant locations, and flies defecated at volumes comparable to or greater than bees. Our results demonstrate that
Eristalis
flower flies are not hosts of
C. bombi
, but they may be mechanical vectors of this parasite at flowers. Thus, flower flies may amplify or dilute
C. bombi
in bee communities, though current theoretical work suggests that unless present in large populations, the effects of mechanical vectors will be smaller than hosts.