Location: Insect Behavior and Biocontrol ResearchTitle: A feeding protocol for delivery of agents to assess development in Varroa mites
|CABRERA, ANA - Bayer Cropscience|
|TEAL, PETER - Former ARS Employee|
Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2017
Publication Date: 4/27/2017
Citation: Cabrera, A.R., Shirk, P.D., Teal, P.T. 2017. A feeding protocol for delivery of agents to assess development in Varroa mites. PLoS One. 12(4):e0176097. https://doi.org/10.1371/journal.pone.0176097.
Interpretive Summary: The Varroa mite is the major ectoparasite pest of the honey bee in North America and is one of the central factors in colony collapse disorder. A Varroa mite infestation weakens the colonies not only as a result of feeding on the bees but by vectoring pathogens. Scientists at the USDA, Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, developed an artificial feeding protocol for the delivery of bioactive agents to the Varroa mites. The feeding protocol did not require the use of a membrane to contain the feeding medium. Various diet components were assessed in the medium and it was established that honey bee blood was necessary but feeding could be enhanced by addition of cultured insect cells. To show that the feeding protocol did not compromise the health of the Varroa mites, the levels of nine previously described gene products were measure and found to be unaffected. However when Tebufenozide, an insect steroid hormone mimic was included in the medium, the levels for the last gene in the steroid pathway increased. This Varroa mite feeding protocol offers a simple reliable means of testing biologically active materials to disrupt reproduction or development and provide control of the pest Varroa mites.
Technical Abstract: A novel feeding protocol for delivery of bio-active agents to Varroa mites was developed by providing mites with honey bee larva hemolymph supplemented with cultured insect cells and selected materials suspended delivered on a fibrous cotton substrate. Mites were starved, fed on treated hemolymph to deliver selected agents and then returned to bee larvae. Transcript levels of two reference genes, actin and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), as well as for seven selected genes involved in reproductive processes showed that the starvation and feeding protocol periods did not pose a high level of stress to the mites as transcript levels remained comparable between phoretic mites and those completing the protocol. The feeding protocol was used to deliver molecules such as hormone analogs or plasmids. Mites fed with Tebufenozide, an ecdysone analog, had higher transcript levels of shade than untreated or solvent treated mites. In order to extend this feeding protocol, cultured insect cells were incorporated to a final ratio of 1 part cells and 2 parts hemolymph. Although supplementation with Bombyx mori Bm5 cells increased the amount of hemolymph consumed per mite, there was a significant decrease in the percentage of mites that fed and survived. On the other hand, Drosophila melanogaster S2 cells reduced significantly the percentage of mites that fed and survived as well as the amount of hemolymph consumed. The feeding protocol provides a dynamic platform with which to challenge the Varroa mite to establish efficacy of control agents for this devastating pest.