CT-supported analysis of the destructive effects of Varroa destructor on the pre-imaginal development of honey bee, Apis mellifera

Abstract

The ectoparasitic mite, Varroa destructor, is a most important health risk for European honey bee subspecies (Apis mellifera) globally. There is a scarcity in experimental approaches addressing this issue by using computed tomography. Our purpose was to determine the decrease in the volume, surface, density and weight alteration triggered by V. destructor in pre-imaginal stages of A. mellifera using computer-based 3-D reconstruction technology. Computer tomography used in the current study proved to be sufficiently sensitive for the detection of V. destructor in comb cells. This non-invasive experimental setup revealed that the developing worker pupae have retained their volume and surface values, whereas the weight loss triggered by V. destructor was statistically confirmed. In addition, the disappearance of lower radiodensity tissues is shown to be due to mite parasitism, which can be primarily explained by haemolymph losses.

Study of Morphological Features in Pre-Imaginal Honey Bee Impaired by Varroa destructor by Means of Computer Tomography

“…The main expectation was a high infestation rate of the Varroa mite during the selection of the experimental colony. The degree of parasitism was assessed based on our previous, systematic observations [11], which were continuously monitored during the experimentation. Powdered sugar was used for the evaluation of the mite infestation rate.…”

“…As a first step, we determined the infestation rate of the Varroa mite using CT recordings based on the work of Keszthelyi et al [11]. Based on this preparatory work, 15-15 parasitized and intact pieces of brood comb adjacent to each other (in an effort to exclude different developmental conditions such as temperature, relative humidity, etc.)…”

“…This devastating parasite plays an important part in colony collapse disorder (CCD) syndrome, which has been detected worldwide [6][7][8]. Specimens impaired by varroosis are characterized by altered body size and weight, weakened immune system, and severe morphological and behavioral disorders [7,[9][10][11]. The triggering factors of these impairments are the sucking of the hemolymph by the mites and parasitism of the fat cells of hosts as well as the vectoring of 20 different virus types [12][13][14].…”

“…There are some studies [11,28] in connection with experimental investigations assisted by CT; nevertheless, the initial developing features of V. destructor are mainly unexplored. The explanation for this is to be mostly found in the hidden development of this species, whose harmful activities and consequences for the host are demanding to detect and measure within the comb.…”