A feeding protocol for delivery of agents to assess development in Varroa mites

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 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 nine 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 honey bee pest.

Transcriptome profiling of the honeybee parasite Varroa destructor provides new biological insights into the mite adult life cycle

“…Many efforts are currently being made to improve our knowledge of Varroa biology and life cycle, as well as to identify chemical treatments again this parasite. For this purpose, many studies have attempted to either rear the mite on its host or not under laboratory conditions [ 49 – 52 ]. In order to assess whether or not artificial rearing conditions are stressful and induce significant changes in Varroa physiology, we artificially-reared phoretic Varroa on its host for 4 days under laboratory conditions and compared their transcriptome to colony-collected phoretic Varroa .…”

Using an in vitro system for maintaining Varroa destructor mites on Apis mellifera pupae as hosts: studies of mite longevity and feeding behavior

“…Information of feeding site preferences may offer some insight into varroa nutritional needs, used for developing artificial diets. Studies of varroa mites suggest that varroa females feed exclusively on hemolymph (Cabrera et al 2017;Erban et al 2015). Hemolymph surrounds every cell in the hemocoel of most arthropods (Fredrick and Ravichandran 2012;Lawry 2006;Paska et al 2014), and is also a reservoir of nutrients.…”

Juvenile hormone pathway in honey bee larvae: A source of possible signal molecules for the reproductive behavior of Varroa destructor

“…Among the Halloween genes, the homologs of neverland and Cyp18a1 (Techer et al., 2019) have not been identified in the Varroa genome while Cyp18a1 gene is believed to have been lost in the Acari (Grbić et al., 2011). It is therefore highly unlikely that Varroa is able to synthesize the ecdysteroids ecdysone and 20E but both of these hormones have been identified from Varroa (Feldlaufer & Hartfelder, 1997) and analogues of ecdysone have been shown to stimulate vitellogenesis in Varroa (Cabrera et al, 2017). There is therefore strong evidence that Varroa requires and uses host‐produced metabolites of ecdysteroids pathway to initiate the reproductive cycle.…”

“…Varroa is able to synthesize the ecdysteroids ecdysone and 20E but both of these hormones have been identified from Varroa (Feldlaufer & Hartfelder, 1997) and analogues of ecdysone have been shown to stimulate vitellogenesis in Varroa (Cabrera et al, 2017). There is therefore strong evidence that Varroa requires and uses host-produced metabolites of ecdysteroids pathway to initiate the reproductive cycle.…”