Janko Božič

Variations of brain biogenic amines in mature honeybees and induction of recruitment behavior

Mature honeybees (Apis mellifera L.) old enough to forage (>3 weeks) were segregated into three activity groups: waggle dancers (active foragers), followers of the dancers (potential recruits) and resting bees (not involved in foraging). Dopamine (DA) pathways in the brain of honeybees seemed to be involved in regulation of forager recruitment. Brain DA and N-β-alanyldopamine (NBAD) levels in the dancers were always higher than in followers, and an increased number of dancers was observed after feeding the colony dihydroxy-phenylalanine (DOPA). Dopamine is hypothesized to modulate the neural activity in the calyx of the mushroom bodies related to recruitment behavior. No consistant effect of octopamine (OA) or serotonin (5HT) on recruitment behavior was observed. Levels of all biogenic amines were strongly effected by season and day-to-day whether changes. Some diurnal changes were also observed.

Development of an ethanol model using social insects: III. Preferences for ethanol solutions.

Experiments are designed to assess whether free-flying honey bees have an aversion to an ethanol solution when given a choice between targets containing an ethanol solution in sucrose or sucrose only. Animals given a choice between a 1% ethanol solution and sucrose only show no aversion to the ethanol solution either in acquisition or extinction. Honey bees given a choice between a 5% ethanol solution and sucrose only show no differences in the initial choice of targets but some bees do switch over to the sucrose-only target. Performance during extinction indicates that bees landed on the previously reinforced sucrose-only target more than the target previously containing the 5% ethanol solution. An experiment in which bees were given a single 5% ethanol target showed that of 20 bees, 11 returned for the entire 12 trials of the experiment. All bees returned at least 6 times to the 5% ethanol target. Additional experiments were run on harnessed foragers in a palatability study of alcoholic beverages consumed by humans. The results of the palatability experiment indicate that in general, bees prefer more sweet drinks with less alcohol.

Attendants and followers of honey bee waggle dances

SUMMARYThe behaviour of bees surrounding a dancing honey bee (Apis mellifera) was studied, using two colonies in observation hives in a shaded part of an apiary. Video recordings and macrophotography were used to view an area of the dance field. Two distinct behaviours were recognized: that of followers and that of attendants. The attendants stood around the dance field with their antennae stretched towards the dancer, and only occasionally moved with the dancer. Followers continuously ran with the dancer, keeping their heads within the border of the dancers figure-eight path at all times. The angle between the body of the follower and that of the dancer was 90° during most of the dance, except at the exit of the waggle run. At that time the follower had to cross over to the opposite side of the dancer. The distance between the head of the follower and the dancers body was nearly always smaller (1 758 cases out of a total of 1 882) than the length of an extended antenna. During the return run the follow...

Neurotoxic potential of ingested ZnO nanomaterials on bees.

The honey bee is among most important pollinators threatened by environmental pollution, pest control and potentially, by products of nanotechnologies. The aim of the current study was an analysis of the neurotoxic potential of ingested zinc oxide nanomaterials (ZnO NMs) or zinc ions (Zn(2+)) on honey bees. We analysed a variety of biomarkers, including metabolic impairment, feeding rate, and survival, as well as the activities of a stress-related enzyme glutathione S-transferase, and the neurotoxicity biomarker acetylcholinesterase. Acetylcholinesterase activity was found to be elevated in bees exposed to either of the tested substances. In addition, we observed increased feeding rate in the group treated with Zn(2+) but not with ZnO NMs or control group. The observed effects we relate primarily to Zn(2+) ions. Here we provide evidence that zinc ions either originating from Zn salt or Zn-based NPs have a neurotoxic potential and thus might contribute to colony survival.

Effect of activity on the haemolymph sugar titres in honey bees

SUMMARYDancing forager honey bees had significantly lower haemolymph trehalose titres than bees following dancers or resting bees at the same time of day. Followers and dancers had a higher glucose titre than resting bees, probably because of elevated activity. Fructose titres were higher in dancers than followers, probably because dancers had recently collected nectar. During absconding, almost all of the haemolymph trehalose disappeared. This possibly was a result of the high energy demands required for long periods of hovering flight in front of the hive that are characteristic of absconding. Absconding and swarming bees may come to rest in the immediate vicinity of the hive to regenerate haemolymph trehalose titres. The trehalose titre was restored within an hour after absconding. Intense shaking and agitation of small groups of bees in a cage could not duplicate the very high level of activity during absconding. Shaking resulted in reduced glycogen levels in the flight muscles and an increased haemol...

Prochloraz and coumaphos induce different gene expression patterns in three developmental stages of the Carniolan honey bee (Apis mellifera carnica Pollmann)

The Carniolan honey bee, Apis mellifera carnica, is a Slovenian autochthonous subspecies of honey bee. In recent years, the country has recorded an annual loss of bee colonies through mortality of up to 35%. One possible reason for such high mortality could be the exposure of honey bees to xenobiotic residues that have been found in honey bee and beehive products. Acaricides are applied by beekeepers to control varroosis, while the most abundant common agricultural chemicals found in honey bee and beehive products are fungicides, which may enter the system when applied to nearby flowering crops and fruit plants. Acaricides and fungicides are not intrinsically highly toxic to bees but their action in combination might lead to higher honey bee sensitivity or mortality. In the present study we investigated the molecular immune response of honey bee workers at different developmental stages (prepupa, white-eyed pupa, adult) exposed to the acaricide coumaphos and the fungicide prochloraz individually and in combination. Expression of 17 immune-related genes was examined by quantitative RT-PCR. In treated prepupae downregulation of most immune-related genes was observed in all treatments, while in adults upregulation of most of the genes was recorded. Our study shows for the first time that negative impacts of prochloraz and a combination of coumaphos and prochloraz differ among the different developmental stages of honey bees. The main effect of the xenobiotic combination was found to be upregulation of the antimicrobial peptide genes abaecin and defensin-1 in adult honey bees. Changes in immune-related gene expression could result in depressed immunity of honey bees and their increased susceptibility to various pathogens.

The Behavior and Social Communication of Honey Bees (APIS Mellifera Carnica Poll.) under the Influence of Alcohol

In this study, the effects of ethanol on honey bee social communication and behavior within the hive were studied to further investigate the usefulness of honey bees as an ethanol-abuse model. Control (1.5 M sucrose) and experimental (1.5 M sucrose, 2.5% w/v ethanol) solutions were directly administered to individual forager bees via proboscis contact with glass capillary tubes. The duration, frequency, and proportion of time spent performing social and nonsocial behaviors were the dependent variables of interest. No differences in the relative frequency or proportion of time spent performing the target behaviors were observed. However, ethanol consumption significantly decreased bouts of walking, resting, and the duration of trophallactic (i.e., food-exchange) encounters. The results of this study suggest that a low dose of ethanol is sufficient to disrupt both social and nonsocial behaviors in honey bees. In view of these results, future behavioral-genetic investigations of honey bee social behavior are encouraged.

Variation in JH synthesis rate in mature honeybees and its possible role in reprogramming of hypopharyngeal gland function

Abstract Juvenile hormone (JH) synthesis was higher in followers than in dancers, which suggests that higher JH levels in followers might be an internal motivational stimulus to induce them to leave me hive to search for food. The positive correlation of in vitro JH synthesis rate and α-glucosidase activity in the hypopharyngeal gland suggests that JH is involved in the reprogramming of the hypopharyngeal gland from producing larval food (immature adults) to production of α-glucosidase in mature adults.

Immune related gene expression in worker honey bee (Apis mellifera carnica) pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor)

Varroa destructor is one of the most common parasites of honey bee colonies and is considered as a possible co-factor for honey bee decline. At the same time, the use of pesticides in intensive agriculture is still the most effective method of pest control. There is limited information about the effects of pesticide exposure on parasitized honey bees. Larval ingestion of certain pesticides could have effects on honey bee immune defense mechanisms, development and metabolic pathways. Europe and America face the disturbing phenomenon of the disappearance of honey bee colonies, termed Colony Collapse Disorder (CCD). One reason discussed is the possible suppression of honey bee immune system as a consequence of prolonged exposure to chemicals. In this study, the effects of the neonicotinoid thiamethoxam on honey bee, Apis mellifera carnica, pupae infested with Varroa destructor mites were analyzed at the molecular level. Varroa-infested and non-infested honey bee colonies received protein cakes with or without thiamethoxam. Nurse bees used these cakes as a feed for developing larvae. Samples of white-eyed and brown-eyed pupae were collected. Expression of 17 immune-related genes was analyzed by real-time PCR. Relative gene expression in samples exposed only to Varroa or to thiamethoxam or simultaneously to both Varroa and thiamethoxam was compared. The impact from the consumption of thiamethoxam during the larval stage on honey bee immune related gene expression in Varroa-infested white-eyed pupae was reflected as down-regulation of spaetzle, AMPs abaecin and defensin-1 and up-regulation of lysozyme-2. In brown-eyed pupae up-regulation of PPOact, spaetzle, hopscotch and basket genes was detected. Moreover, we observed a major difference in immune response to Varroa infestation between white-eyed pupae and brown-eyed pupae. The majority of tested immune-related genes were upregulated only in brown-eyed pupae, while in white-eyed pupae they were downregulated.

Maturation and stratification of antibacterial activity and total phenolic content of bee bread in honey comb cells

Bee bread is processed pollen stored in honey comb. Pollen foragers unload pollen loads into the appropriate cells and hive bees further process it into bee bread. This results in a layered structure of the reserve, which is at the top covered with honey and a wax cap. The process of pollen collection and packing was monitored during chestnut (Castanea sativa Mill.) flowering and five frames of honey comb with stored bee bread were collected. We dissected the bee bread cells into bottom, middle and upper layers of bee bread and an additional top honey layer. Cells were sampled before covering with honey, after adding honey, and after aging of covered cells for four weeks. Samples were analyzed according to pollen type content, antibacterial activity and total phenolic content. Our results indicated that microbial activity and processing by honey bees were the major contributors to the antibacterial activity observed. Total phenolic content did not correlate with antibacterial activity and was the highest at the bottom of the honey comb cell. Honey bees establish a controlled microenvironment for bee bread fermentation and probably additionally stop microbe activity at the end of the process with feeding glands secretions.