-The objective of this study was to evaluate the effects of chronical exposure of honeybee drones to environmental (5 ppb) and non-environmental concentration (200 ppb) of imidacloprid (IMD) on sperm concentration, motility, viability, and mitochondrial membrane potential measured in semen obtained from 180 drones originating from 18 colonies. The results demonstrate that IMD exposure did not affect sperm concentration; however, there were significant differences in concentration within colonies. IMD exposure was associated with reductions in sperm motility, which also varied within colonies. Statistically significant interactions between IMD exposure and colony were found for active mitochondria and sperm viability. Our results strongly suggest that neonicotinoids can negatively affect honeybee drone sperm quality. It is important to emphasize that IMD actions can be strongly modulated according to the colony.Apis mellifera / imidacloprid / spermatozoa / motility / viability

The study focused on a method of detection for bee colony infestation with the Varroa destructor mite, based on the measurements of the chemical properties of beehive air. The efficient detection of varroosis was demonstrated. This method of detection is based on a semiconductor gas sensor array and classification module. The efficiency of detection was characterized by the true positive rate (TPR) and true negative rate (TNR). Several factors influencing the performance of the method were determined. They were: (1) the number and kind of sensors, (2) the classifier, (3) the group of bee colonies, and (4) the balance of the classification data set. Gas sensor array outperformed single sensors. It should include at least four sensors. Better results of detection were attained with a support vector machine (SVM) as compared with the k-nearest neighbors (k-NN) algorithm. The selection of bee colonies was important. TPR and TNR differed by several percent for the two examined groups of colonies. The balance of the classification data was crucial. The average classification results were, for the balanced data set: TPR = 0.93 and TNR = 0.95, and for the imbalanced data set: TP = 0.95 and FP = 0.53. The selection of bee colonies and the balance of classification data set have to be controlled in order to attain high performance of the proposed detection method.

-Oxidative stress is defined as a disturbance in the balance between the production of reactive oxygen species and antioxidant defences. We measured total antioxidant capacity (TAC) in honeybee haemolymph and seminal plasma and analysed TAC of haemolymph in relation to age and exposure to pesticide. TAC of haemolymph increased with age of bees (1.18 vs 1.97 mM of (±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox) for 1-and 30-day-old bees, respectively, P ≤0.05). Exposure to imidacloprid (IMD) affected TAC of haemolymph of 1-day-old but not 30-day-old honeybees. TAC in haemolymph of 1-day-old bees was lower in treatments with the addition of 5 and 200 ppb IMD (1.57-1.46 mM of Trolox in treated bees compared with 2.37 mM of Trolox in controls; P ≤0.05). In conclusion, antioxidant protection of honeybees seems to be related to age and may be disturbed by exposure to IMD. Older bees with higher antioxidant protection seem to be less susceptible to IMD toxicity. The toxic effect of pesticide seems to be particularly dangerous in early life stages of honeybees.Apis mellifera / total antioxidant capacity / haemolymph / ageing / pesticide

Imidacloprid (IMD) may affect proteolysis, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and global DNA methylation in honeybees. Queens, drones, and workers aged 1 or 20 days were exposed (free-flying colonies) to IMD (5 ppb and 200 ppb) in their diet. As a result, the colony depopulation did not occurred. IMD disturbed hemolymph/cuticle proteolysis; deactivated most of the cuticle protease inhibitors, activated hemolymph thiol and metal proteases and cuticle thiol proteases; downregulated ALP, ALT, AST; and increased DNA methylation in a caste-and age-dependent manner. The response in queens and workers differed, possibly due to eusocial evolution. Higher IMD dose had greater effects. The responses of ALP, ALT, AST, and DNA may reflect acceleration of biochemical senescence and epigenetic adaptation to IMD. All these biochemical side effects may lead to colony depopulation during future biotic/abiotic stress.

No abstract

Honey bees are subject to a number of stressors. In recent years, there has been a worldwide decline in the population of these insects. Losses raise a serious concern, because bees have an indispensable role in the food supply of humankind. This work is focused on the method of assessment of honey bee colony infestation by Varroa destructor. The approach allows to detect several categories of infestation: “Low”, “Medium” and “High”. The method of detection consists of two components: (1) the measurements of beehive air using a gas sensor array and (2) classification, which is based on the measurement data. In this work, we indicate the sensitivity of the bee colony infestation assessment to the timing of measurement data collection. It was observed that the semiconductor gas sensor responses to the atmosphere of a defined beehive, collected during 24 h, displayed temporal variation. We demonstrated that the success rate of the bee colony infestation assessment also altered depending on the time of day when the gas sensor array measurement was done. Moreover, it was found that different times of day were the most favorable to detect the particular infestation category. This result could indicate that the representation of the disease in the beehive air may be confounded during the day, due to some interferences. More studies are needed to explain this fact and determine the best measurement periods. The problem addressed in this work is very important for scheduling the beekeeping practices aimed at Varroa destructor infestation assessment, using the proposed method.

No abstract

The effect of sublethal doses of imidacloprid on protein content and activity of proteases on honey bees was analyzed. The study was conducted in three experimental groups: colonies from groups BE-5 and BE-200 were contaminated with 5 and 200 ppb of imidacloprid, respectively, via their food supply (syrup and pollen), while group BE was used as control (untreated). Bee samples were collected 3 and 10 weeks after feeding started. Protein concentration in bee tissue extracts was analyzed with reference: (a) to the dose of imidacloprid; and (b) duration of exposure to the chemical. The average quantity of protein content was significantly higher at the 3-week interval than in the 10-week interval and the bees from control colonies (BE) had significantly higher protein contents than contaminated bees (BE-5 and BE-200), even 3 weeks after feeding with imidacloprid started. Similarly, the activity of proteolytic enzymes (proteases) was found to be dependent on the dose of imidacloprid used, compared to bees from control colonies showing significantly higher activity.Influencia de las dosis subletales de Imidacloprid en el contenido de proteína y la actividad proteolítica en las abejas melíferas (Apis mellifera L.)Se ha analizado el efecto de las dosis subletales de imidacloprid en el contenido de proteínas y la actividad de las proteasas en las abejas melíferas. El estudio se realizó en tres grupos experimentales: las colonias de los grupos de BE-5 y BE-200 se contaminaron con 5 y 200 ppb de imidacloprid, respectivamente, a través del alimento suministrado (jarabe y polen), mientras que el grupo SER se utilizó como control (sin tratar). Se recogieron muestras de abejas en las semanas 3 y 10 después del comienzo de la alimentació n. La concentració n de proteína en extractos de tejido de abejas se analizó en relació n con: a) la dosis de imidacloprid; y b) la duració n de la exposició n a la sustancia química. La cantidad promedio del contenido de proteína fue significativamente mayor en el intervalo de 3 semanas que en el intervalo de 10 semanas y las abejas de las colonias control (BE) tuvieron un contenido de proteína significativamente más alto que las abejas contaminadas (BE-5 y BE-200), incluso 3 semanas después de que comenzara la alimentació n con imidacloprid. Del mismo modo se encontró que la actividad de las enzimas proteolíticas (proteasas) depende de la dosis de imidacloprid usada, en comparació n con las abejas de colonias de control que muestran una actividad significativamente más alta.