Protocerebral Mediodorsal A2′ Neurosecretory Neurons in Late Pupae of Yellow Mealworm (Tenebrio molitor) after Exposure to a Static Magnetic Field

Estimation of changes in fitness components and antioxidant defense of Drosophila subobscura (Insecta, Diptera) after exposure to 2.4 T strong static magnetic field

As an ecological factor, a magnetic field can affect insects causing a wide range of responses. The main purpose of this study was to analyze the fitness components (postembryonic development and viability of individuals) and the antioxidant defense (superoxide dismutase, catalase, and total glutathione) in laboratory strains of Drosophila subobscura, originating from oak and beech forests after exposure to the strong static magnet (2.4 T, VINCY Cyclotron magnet). The first instar larvae were placed near the north pole (N group) or the south pole (S group) of the magnet for 2 h. Oak and beech populations of D. subobscura had longer development time and lower viability in N and S groups compared to controls. These differences were significant only in S group of oak population and in N group of beech population. Total glutathione content was significantly decreased in both exposed groups of oak population, while catalase activity was significantly increased in both exposed groups of beech population. Being significantly decreased in both exposed groups of oak population and significantly increased in S group of beech population in comparison to controls, superoxide dismutase activity was observed in different values. According to the results, it can be stated that applied static magnetic field could be considered a potential stressor influencing the fitness components and antioxidant defense in Drosophila flies.

Effects of two different waveforms of ELF MF on bioelectrical activity of antennal lobe neurons of Morimus funereus (Insecta, Coleoptera)

PURPOSE

External magnetic fields (MF) interact with organisms at all levels, including the nervous system. Bioelectrical activity of antennal lobe neurons of adult Morimus funereus was analyzed under the influence of extremely low frequency MF (ELF MF, 50 Hz, 2 mT) of different characteristics (exposure duration and waveform).

MATERIAL AND METHODS

Neuronal activity (background/neuronal population and those nearest to the recording electrode) in adult longhorn beetles was registered through several phases of exposure to the sine wave and square wave MF for 5, 10 and 15 min.

RESULTS

The sine wave MF, regardless of the exposure duration, did not change the reversibility factor of antennal lobe neuronal activity in adult M. funereus. In contrast, reversibility factors of the nearest neurons were significantly changed after the exposure to square wave MF for 10 and 15 min.

CONCLUSION

M. funereus individuals are sensitive to both sine wave and square wave ELF MF (50 Hz, 2 mT) of different duration, whereby their reactions depend on the characteristics of the applied MF and specificity of each individual.

Effect of magnetic fields on antioxidative defense and fitness-related traits of Baculum extradentatum (insecta, phasmatodea)

This study aimed to determine the effect of magnetic fields on the antioxidative defense and fitness-related traits of Baculum extradentatum. Following exposure to magnetic fields, antioxidative defense (superoxide dismutase (SOD), catalase (CAT) activities, and total glutathione (GSH) content) and fitness-related traits (egg mortality, development dynamics, and mass of nymphs) were monitored in nymphs. The experimental groups were: control (kept out of influence of the magnets), a group exposed to a constant magnetic field (CMF) of 50 mT, and a group exposed to an alternating magnetic field (AMF) of 50 Hz, 6 mT. We found increased SOD and CAT activities in animals exposed to constant and AMFs, whereas GSH activity was not influenced by experimental magnetic fields. No differences were found in egg mortality between control and experimental groups. Significant differences in the time of development between the control and the CMF group were observed, as well as between the CMF and the AMF group. No differences were found in the mass of the nymphs between the three experimental groups. In conclusion, CMF and AMF have the possibility to modulate the antioxidative defense and some of the fitness-related traits in B. extradentatum.

The effects of acute exposure to magnetic fields on morphometric characteristics of bombyxin-producing neurosecretory neurons in gypsy moth caterpillars

PURPOSE

To examine the effects of acute exposure to strong static magnetic fields and extremely low frequency magnetic fields, on neurosecretory neurons which synthesise insulin-like neurohormone.

MATERIALS AND METHODS

Immunocytochemical detection of bombyxin-like material in the protocerebral neurosecretory neurons of Lymantria dispar caterpillars was performed using a monoclonal antibody directed against a synthetic dekapeptide corresponding to the N-terminus of the bombyxin A-chain. Caterpillars were exposed to strong static magnetic fileds (235 mT) and extremely low frequency magnetic fields (2 mT) for three days after moulting into the 4th instar.

RESULTS

We report the presence of immunoreactive molecules in A2 type of medial neurosecretory neurons (nsn) in caterpillars' brain of L. dispar. The three-day exposure of caterpillars to stresogenic external magnetic fields changed the size of A2 type nsn, their nuclei and the intensity of protein band in the region of bombyxin molecular mass (4-6 kD) after exposure to extremely low frequency magnetic fields in comparison to control group and group treated by strong static magnetic fields.

CONCLUSION

These are the first data on the influence of external magnetic fields on the polyphagous phytophagous forest pest L. dispar L. (Lepidoptera: Lymantridae) indicating an intensive synthesis of insulin-like neurosecretory material.

The response of dorsomedial A1’ and dorsolateral L2’ neurosecretory neurons of Lymantria dispar L. caterpillars to the acute effects of magnetic fields

The morphometric changes (size of neurons and their nuclei) of protocerebral dorsomedial A1? and dorsolateral L2? neurosecretory neurons were analyzed in Lymantria dispar larvae after exposure to strong static (SMF, 235 mT) and extremely low frequency magnetic fields (ELF MF, 2 mT). Increase in the size of A1? neurons and their nuclei were observed after acute exposure to SMF. Decrease in the size of these neurons and their nuclei was observed after exposure to ELF MF. The size of L2? neurons and their nuclei tend to decrease after exposure to SMF and ELF MF. The quantification of protein bands within the Mr range corresponding to the large form of the prothoracicotropic neurohormone indicates that the amount of protein decreased after exposure to both types of magnetic fields.

Viability of old house borer (Hylotrupes bajulus) larvae exposed to a constant magnetic field of 98 mT under laboratory conditions

The purpose of our experiment was to establish how exposure to a constant magnetic field of 98 mT affects behavior in terms of viability and larval mass of the old house borer (Hylotrupes bajulus L.). It is demonstrated that larvae exposed to this magnetic field show statistically significant higher viability, as well as a tendency of mass increase in comparison with the control group. These results can be attributed to the modulatory effect of the employed external magnetic field on metabolism and neurohumoral regulation in the insects.