Increased aggression and reduced aversive learning in honey bees exposed to extremely low frequency electromagnetic fields

Precision Beekeeping Systems: State of the Art, Pros and Cons, and Their Application as Tools for Advancing the Beekeeping Sector

The present review aims to summarize the more recent scientific literature and updated state of the art on the research effort spent in adapting hardware-software tools to understand the true needs of honeybee colonies as a prerequisite for any sustainable management practice. A SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis was also performed with the aim of identifying the key factors that could support or impair the diffusion of precision beekeeping (PB) systems. Honeybee husbandry, or beekeeping, is starting to approach precision livestock farming (PLF), as has already happened in other animal husbandry sectors. A transition from the current paradigm of rational beekeeping to that of precision beekeeping (PB) is thus expected. However, due to the peculiarities of this species and the related farming practices, the PB technological systems (PB systems) are still undergoing a development process that, to some extent, limits their large-scale practical application. Several physical-chemical (weight, temperature, humidity, sound, gases) and behavioral traits (flight activity, swarming) of the hive are reviewed in light of the evolution of sensors, communication systems, and data management approaches. These advanced sensors are equipped with a microprocessor that records data and sends it to a remote server for processing. In this way, through a Wireless Sensor Network (WSN) system, the beekeeper, using specific applications on a personal computer, tablet, or smartphone, can have all the above-mentioned parameters under remote control. In general, weight, temperature, and humidity are the main hive traits monitored by commercial sensors. Surprisingly, flight activity sensors are rarely available as an option in modular PB systems marketed via the web. The SWOT analysis highlights that PB systems have promising strength points and represent great opportunities for the development of beekeeping; however, they have some weaknesses, represented especially by the high purchasing costs and the low preparedness of the addressed operators, and imply some possible threats for beekeeping in terms of unrealistic perception of the apiary status if they applied to some hives only and a possible adverse impact on the honeybees' colony itself. Even if more research is expected to take place in the next few years, indubitably, the success of commercial PB systems will be measured in terms of return on investment, conditioned especially by the benefits (higher yields, better colonies' health) that the beekeeper will appraise as a consequence of their use.

Defined exposure of honey bee colonies to simulated radiofrequency electromagnetic fields (RF-EMF): Negative effects on the homing ability, but not on brood development or longevity

Urbanization and the increasing use of wireless technologies lead to higher emission rates of radiofrequency electromagnetic fields (RF-EMF) in populated areas. This anthropogenic electromagnetic radiation is a form of environmental pollution and a potential stressor on bees or other flying insects. Cities often have a high density of wireless devices operating on microwave frequencies, which generate electromagnetic frequencies e.g. in the 2.4 and 5.8 GHz bands commonly used by the wireless technologies. To date the effects of nonionizing electromagnetic radiation on the vitality and behavior of insects are poorly understood. In our experiment we used honey bees as model organisms and analyzed the effects of defined exposures to 2.4 and 5.8 GHz on brood development, longevity and homing ability under field conditions. To generate this radiation, we used a high-quality radiation source which generates a consistent, definable and realistic electromagnetic radiation, engineered for this experiment by the Communications Engineering Lab (CEL) at the Karlsruhe Institute of Technology. Our results show significant effects of long-term exposures on the homing ability of foraging honey bees, but no effects on brood development and adult worker longevity. Using this novel and high-quality technical set-up, this interdisciplinary work provides new data on the effects of these widely used frequencies on important fitness parameters of free-flying honey bees.

Electromagnetic field exposure affects the calling song, phonotaxis, and level of biogenic amines in crickets

The electromagnetic field (EMF) is ubiquitous in the environment, constituting a well-known but poorly understood stressor. Few studies have been conducted on insect responses to EMF, although they are an excellent experimental model and are of great ecological importance. In our work, we tested the effects of EMF (50 Hz, 7 mT) on the cricket Gryllus bimaculatus: the male calling song pattern, female mate choice, and levels of biogenic amines in the brain. Exposure of males to EMF increased the number and shortened the period of chips in their calling song (by 2.7% and 5% relative to the control song, respectively), but not the sound frequency. Aged (3-week-old) females were attracted to both natural and EMF-modified male signals, whereas young (1-week-old, virgin) females responded only to the modified signal, suggesting its higher attractance. Stress response of males to EMF may be responsible for the change in the calling song, as suggested by the changes in the amine levels in their brains: an increase in dopamine (by 50% relative to the control value), tyramine (65%), and serotonin (25%) concentration and a decrease in octopamine level (by 25%). These findings indicate that G. bimaculatus responds to EMF, like stressful conditions, which may change the condition and fitness of exposed individuals, disrupt mate selection, and, in consequence, affect the species' existence.

Ambient Electromagnetic Radiation as a Predictor of Honey Bee (Apis mellifera) Traffic in Linear and Non-Linear Regression: Numerical Stability, Physical Time and Energy Efficiency

Since bee traffic is a contributing factor to hive health and electromagnetic radiation has a growing presence in the urban milieu, we investigate ambient electromagnetic radiation as a predictor of bee traffic in the hive's vicinity in an urban environment. To that end, we built two multi-sensor stations and deployed them for four and a half months at a private apiary in Logan, UT, USA. to record ambient weather and electromagnetic radiation. We placed two non-invasive video loggers on two hives at the apiary to extract omnidirectional bee motion counts from videos. The time-aligned datasets were used to evaluate 200 linear and 3,703,200 non-linear (random forest and support vector machine) regressors to predict bee motion counts from time, weather, and electromagnetic radiation. In all regressors, electromagnetic radiation was as good a predictor of traffic as weather. Both weather and electromagnetic radiation were better predictors than time. On the 13,412 time-aligned weather, electromagnetic radiation, and bee traffic records, random forest regressors had higher maximum R2 scores and resulted in more energy efficient parameterized grid searches. Both types of regressors were numerically stable.

Biological Effects of Electric, Magnetic, and Electromagnetic Fields from 0 to 100 MHz on Fauna and Flora: Workshop Report

This report summarizes effects of anthropogenic electric, magnetic, and electromagnetic fields in the frequency range from 0 to 100 MHz on flora and fauna, as presented at an international workshop held on 5-7 November in 2019 in Munich, Germany. Such fields may originate from overhead powerlines, earth or sea cables, and from wireless charging systems. Animals and plants react differentially to anthropogenic fields; the mechanisms underlying these responses are still researched actively. Radical pairs and magnetite are discussed mechanisms of magnetoreception in insects, birds, and mammals. Moreover, several insects as well as marine species possess specialized electroreceptors, and behavioral reactions to anthropogenic fields have been reported. Plants react to experimental modifications of their magnetic environment by growth changes. Strong adverse effects of anthropogenic fields have not been described, but knowledge gaps were identified; further studies, aiming at the identification of the interaction mechanisms and the ecological consequences, are recommended.

Extremely Low-Frequency Electromagnetic Field Impairs the Development of Honeybee (Apis cerana)

Simple Summary

The ELF-EMF pollution generated by the increase in electrically powered devices and power lines, accompanied by economic development, has a widespread effect on surrounding organisms. Honeybees are one of the most important pollinators. The decline in the honeybee population caused by a variety factors, including EMFs, has attracted attention worldwide. It was already known that ELF-EMFs could impair the ability of learning and cognition, causing foraging bees to lose their ability to find their way home. The pollination ability of foraging bees is derived from the rearing quantity of larvae and continuous eclosion of new adult bees in the colony. However, the effect of ELF-EMFs on honeybee larvae is not clear. The aims and objectives of this study were therefore to investigate it. The results showed that ELF-EMF exposure decreases honeybee survival rate and body weight and extends the duration of development time. Transcriptome sequencing showed that ELF-EMF exposure decreases the biological process of nutrient and energy metabolism, impedes the degradation of larvae tissues and the rebuilding of pupae tissues in the metamorphosis process, and seriously interferes with the growth and development of honeybee larvae. This provides an experimental basis and new perspective for protecting honeybee populations from ELF-EMF pollution.

Abstract

Increasing ELF-EMF pollution in the surrounding environment could impair the cognition and learning ability of honeybees, posing a threat to the honeybee population and its pollination ability. In a social honeybee colony, the numbers of adult bees rely on the successful large-scale rearing of larvae and continuous eclosion of new adult bees. However, no studies exist on the influence of ELF-EMFs on honeybee larvae. Therefore, we investigated the survival rate, body weight, and developmental duration of first instar larvae continuously subjected to ELF-EMF exposure. Moreover, the transcriptome of fifth instar larvae were sequenced for analyzing the difference in expressed genes. The results showed that ELF-EMF exposure decreases the survival rate and body weight of both white-eye pupae and newly emerged adults, extends the duration of development time and seriously interferes with the process of metamorphosis and pupation. The transcriptome sequencing showed that ELF-EMF exposure decreases the nutrient and energy metabolism and impedes the degradation of larvae tissues and rebuilding of pupae tissues in the metamorphosis process. The results provide an experimental basis and a new perspective for the protection of honeybee populations from ELF-EMF pollution.

The Impact of Magnetic Field on Insecticide Toxicity Measured by Biological and Biochemical Parameters of Earias insulana (Boisd)

This study illustrates the effect of magnetic field (MF) on the toxicity of two insecticides, emamectin benzoate (Emazoate 2.15% EC) and spinosad (SpinTor 24% SC), and determines their adverse effects on the bollworm (Earias insulana) through various biological and biochemical assays. The investigation indicated that exposure to the insecticides in a MF of 180 mT resulted in stronger toxicity, with LC₅₀ values of 0.162, 1.211, and 1.770 ppm, respectively. In addition, the results showed that magnetized insecticides significantly increased in the duration of the total immature stages (larvae and/or pupae) 32.1 and 36.6 days, compared with 27.9 and 30.5 days, respectively, in the nonmagnetized insecticides, while untreated check was 21 days. Also, the magnetized insecticides reduced the percentage of adult emergence, and increased deformations in the larval and pupal stages. Furthermore, sex ratio was greatly affected by exposure to both insecticides in conjunction with the MF. Exposure of the larvae of E insulana to magnetized insecticides can bring about malfunction in some biochemical process and significantly decreased the invertase activity, and decreased the total protein and carbohydrates. In contrast, it can increase amylase compared with nonmagnetized insecticides and untreated controls. Results concluded that the two insecticides' MF affected growth, survival time, and biological and biochemical parameters of E. insulana. © 2022 Bioelectromagnetics Society.

Exposure to Magnetic Fields Changes the Behavioral Pattern in Honeybees (Apis mellifera L.) under Laboratory Conditions

Simple Summary

Electrically powered devices and power lines generate electromagnetic fields. Technological development has resulted in environmental pollution with anthropogenic electromagnetic fields. One of its components is the magnetic field. Its impact on living organisms is still under investigation, but there are reports suggesting that the direction of change is negative. Pollinators are very important for the environment and are also exposed to this factor. In this study, we wanted to investigate the impact of magnetic field exposure on the behavior of one of the key pollinators: the honeybee. The frequency of the tested field corresponded to those present under high voltage lines, as honeybees often forage in these areas. The results showed that the magnetic field caused a distribution in behavioral patterns, which may have a direct impact on foraging efficiency and pollination success.

Abstract

Earth’s magnetic field (MF) plays an important role for many species, including the honeybee, in navigation. Nowadays, much larger alternating fields are emitted by miscellaneous electric infrastructure components, such as transformers and power lines, and the environment is therefore polluted by an anthropogenic electromagnetic field, though little is known regarding its impact on living organisms. The behavior of animals is the first and easiest way to establish the impact of stress. It shows if the animal can detect the exposure and react to it. To investigate this, one-day-old bees were exposed to a 50 Hz magnetic field of induction at 1 mT and 1.7 mT for 10 min, 1 h, and 3 h under laboratory conditions. All groups exposed to the magnetic field showed differences in behavioral patterns. What is more, they presented a behavior absent in the control: loss of balance. There were differences, both in the ratio of behaviors and in the number of bouts—exposed bees more often changed behavior. Occurrence of differences is an indication of the reaction of the honeybee organism to the magnetic field. Loss of balance is a disturbing symptom, and behavior changes indicate a disturbance of the honeybee by the electromagnetic field.

Effect of the electric field at 50 Hz and variable intensities on biochemical markers in the honey bee's hemolymph

The amount of artificial electromagnetic fields of various parameters in the honey bee's environment increases globally. So far, it had been proven that exposure to an E-field at 50 Hz can cause changes in bee's behavior, alter the activity of proteases, and enzymatic antioxidants. Due to the potentially harmful effect of this factor on honey bees, we decided to investigate the activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP), and the concentration of albumin and creatinine in bee's hemolymph after exposure to 50 Hz E-field. Honey bee workers were placed in wooden cages (200 × 150 × 70 mm) and exposed to the 50 Hz E-field with the intensity of <1, 5.0, 11.5, 23.0, or 34.5 kV/m for 1, 3, 6, or 12h. A homogeneous 50 Hz E-field was generated in the form of a plate capacitor. Hemolymph samples for analysis were taken immediately after the end of exposure to the E-field from 100 bees from each group. According to our study, the activity of AST, ALT, and ALP in honey bees' hemolymph decreased after exposure to 50 Hz E-field with various intensities. The decrease in AST, ALT, and ALP activity intensified with prolonged exposure time. 50 Hz E-field may cause the impairment of crucial metabolic cycles in the honey bees' organism (such as the citric acid cycle, ATP synthesis, oxidative phosphorylation, β-oxidation). Moreover, exposure to E-Field altered the concentration of creatinine and albumin, which are important non-enzymatic antioxidants. Such changes may indicate a disturbance in protein metabolism and increased muscle activity.

Extremely Low-Frequency Electromagnetic Fields Entrain Locust Wingbeats

Extremely low-frequency electromagnetic fields (ELF EMFs) have been shown to impact the behavior and physiology of insects. Recent studies have highlighted the need for more research to determine more specifically how they affect flying insects. Here, we ask how locust flight is affected by acute exposure to 50 Hz EMFs. We analyzed the flights of individual locusts tethered between a pair of copper wire coils generating EMFs of various frequency using high-speed video recording. The mean wingbeat frequency of tethered locusts was 18.92 ± 0.27 Hz. We found that acute exposure to 50 Hz EMFs significantly increased absolute change in wingbeat frequency in a field strength-dependent manner, with greater field strengths causing greater changes in wingbeat frequency. The effect of EMFs on wingbeat frequency depended on the initial wingbeat frequency of a locust, with locusts flying at a frequency lower than 20 Hz increasing their wingbeat frequency, while locusts flying with a wingbeat frequency higher than 20 Hz decreasing their wingbeat frequency. During the application of 50 Hz EMF, the wingbeat frequency was entrained to a 2:5 ratio (two wingbeat cycles to five EMF cycles) of the applied EMF. We then applied a range of ELF EMFs that were close to normal wingbeat frequency and found that locusts entrained to the exact frequency of the applied EMF. These results show that exposure to ELF EMFs lead to small but significant changes in wingbeat frequency in locusts. We discuss the biological implications of the coordination of insect flight in response to electromagnetic stimuli. © 2021 Bioelectromagnetics Society.