Long-term exposure of cockroach Blaptica dubia (Insecta: Blaberidae) nymphs to magnetic fields of different characteristics: effects on antioxidant biomarkers and nymphal gut mass.

Purpose: The main goal of this study was to analyze the long-term effects of static (SMF) and extremely low-frequency magnetic field (ELF MF) on nymphal gut mass and antioxidant biomarkers in this tissue of cockroach Blaptica dubia.Materials and methods: One-month-old nymphs were exposed to magnetic field (MF) for 5 months in three experimental groups: control, exposure to SMF (110 mT) and exposure to ELF MF (50 Hz, 10 mT). Results: The gut masses of the MF groups were significantly lower when compared to control. Superoxide dismutase (SOD) and catalase (CAT) activities were markedly higher than for the control and the differences between the MF groups were statistically significant only for SOD. The applied MF had no effect on total glutathione (GSH) content. Glutathione reductase (GR) and glutathione S-transferase (GST) activities were significantly lower in both MF groups in comparison to the control. There was a significant difference between MF groups for GR activity. Principal Component Analysis (PCA) showed that CAT and GST were the main factors contributing to the differentiation of the control group from the treated experimental groups along PCA 1, and SOD and GR along PCA 2. PCA revealed clear separation between experimental groups depends on antioxidant biomarker response. Conclusion: The applied magnetic fields could be considered a potential stressor influencing gut mass, as well as examined antioxidative biomarkers.

Cryptochrome 2 mediates directional magnetoreception in cockroaches.

The ability to perceive geomagnetic fields (GMFs) represents a fascinating biological phenomenon. Studies on transgenic flies have provided evidence that photosensitive Cryptochromes (Cry) are involved in the response to magnetic fields (MFs). However, none of the studies tackled the problem of whether the Cry-dependent magnetosensitivity is coupled to the sole MF presence or to the direction of MF vector. In this study, we used gene silencing and a directional MF to show that mammalian-like Cry2 is necessary for a genuine directional response to periodic rotations of the GMF vector in two insect species. Longer wavelengths of light required higher photon fluxes for a detectable behavioral response, and a sharp detection border was present in the cyan/green spectral region. Both observations are consistent with involvement of the FADox, FAD(•-) and FADH(-) redox forms of flavin. The response was lost upon covering the eyes, demonstrating that the signal is perceived in the eye region. Immunohistochemical staining detected Cry2 in the hemispherical layer of laminal glia cells underneath the retina. Together, these findings identified the eye-localized Cry2 as an indispensable component and a likely photoreceptor of the directional GMF response. Our study is thus a clear step forward in deciphering the in vivo effects of GMF and supports the interaction of underlying mechanism with the visual system.

Candidates for the light entrainment pathway to the circadian clock of the Madeira cockroach Rhyparobia maderae.

The circadian pacemaker controlling locomotor activity rhythms in the Madeira cockroach is located at the accessory medulla (AMe). The ipsi- and contralateral compound eyes provide light input to the AMe, possibly via the γ-aminobutyric acid (GABA)-immunoreactive (-ir) distal tract, which connects the glomeruli of the AMe to the ipsilateral medulla and lamina. To identify possible light-entrainment pathways, double-label immunocytochemistry was performed employing antibodies against GABA, myoinhibitory peptide (MIP), allatotropin (AT) and orcokinin (ORC). While all antisera tested, except the anti-ORC, prominently stained the glomeruli of the AMe, colocalization with anti-GABA was detected neither in the glomeruli nor in the distal tract. However, one median neuron that colocalized GABA-, AT- and MIP-immunoreactivity appeared to connect all glomeruli of the AMe to the medulla and lamina. Furthermore, one distal-frontoventral local neuron with arborizations in all glomeruli of the AMe colocalized anti-AT- and anti-MIP immunoreactivity. As candidates for contralateral light entrainment pathways, one ventromedian and one ventral neuron colocalized MIP- and ORC immunoreactivity, projecting via posterior and anterior commissures. Both branched in the interglomerular region of the AMe, where arborizations co-labeled with anti-ORC- and anti-MIP antisera. A possible role for MIP in light entrainment is supported also by injections of Rhyparobia maderae-specific MIP-2, which generated an all-advance phase-response curve late at night. Future experiments will challenge our hypothesis that GABA-, MIP- and AT-ir neurons provide ipsilateral light entrainment to all glomeruli, while MIP- and ORC-ir neurons carry contralateral light entrainment to the AMe's interglomerular region, either delaying or advancing AMe neurons light-dependently.

Two-photon fluorescence lifetime imaging of intracellular chloride in cockroach salivary glands.

Although chloride plays an important role in many cellular processes, there is a lack of data about intracellular chloride concentrations [Cl(-)](i), particularly due to technical problems. To overcome that, in this study fluorescence lifetime imaging microscopy in the time-domain by using time-correlated single-photon counting was combined with two-photon excitation (2P-FLIM). This 2P-FLIM setup has been successfully used with the Cl(-)-sensitive fluorescent dye N-(ethoxycarbonylmethyl)-6-methoxy-quinolinium bromide (MQAE) in order to measure [Cl(-)](i) in cockroach salivary glands, a well-established model system for studying epithelial ion transport processes. MQAE was well suitable for two-photon excitation, when loaded into cells, and displayed a sufficient dynamic range of its fluorescence decay time changes in response to variation of [Cl(-)](i) according to the Stern-Volmer relationship. On this basis a uniform [Cl(-)](i) in the range of 42-80 mM with a mean value of 59 mM +/- 1 mM was found in resting cockroach salivary ducts, indicating active Cl(-) accumulation. However, exposure to Cl(-)-free saline caused only a moderate [Cl(-)](i) drop to 48 mM +/- 4 mM, suggesting a relatively low basolateral Cl(-) permeability in ducts, at least under resting conditions. Additionally, bath application of the biogenic amine dopamine, known to stimulate the saliva modification in the ducts, caused no significant [Cl(-)](i) changes. These results suggest a more complex scenario of [Cl(-)](i) homeostasis in cockroach salivary ducts. In conclusion, 2P-FLIM seems to be a suitable technique for quantitative [Cl(-)](i) measurements in many biological systems.

Neural organization of the circadian system of the cockroach Leucophaea maderae.

The cockroach Leucophaea maderae was the first animal in which lesion experiments localized an endogenous circadian clock to a particular brain area, the optic lobe. The neural organization of the circadian system, however, including entrainment pathways, coupling elements of the bilaterally distributed internal clock, and output pathways controlling circadian locomotor rhythms are only recently beginning to be elucidated. As in flies and other insect species, pigment-dispersing hormone (PDH)-immunoreactive neurons of the accessory medulla of the cockroach are crucial elements of the circadian system. Lesions and transplantation experiments showed that the endogeneous circadian clock of the brain resides in neurons associated with the accessory medulla. The accessory medulla is organized into a nodular core receiving photic input, and into internodular and peripheral neuropil involved in efferent output and coupling input. Photic entrainment of the clock through compound eye photoreceptors appears to occur via parallel, indirect pathways through the medulla. Light-like phase shifts in circadian locomotor activity after injections of gamma-aminobutyric acid (GABA)- or Mas-allatotropin into the vicinity of the accessory medulla suggest that both substances are involved in photic entrainment Extraocular, cryptochrome-based photoreceptors appear to be present in the optic lobe, but their role in photic entrainment has not been examined. Pigment-dispersing hormone-immunoreactive neurons provide efferent output from the accessory medulla to several brain areas and to the peripheral visual system. Pigment-dispersing hormone-immunoreactive neurons, and additional heterolateral neurons are, furthermore, involved in bilateral coupling of the two pacemakers. The neuronal organization, as well as the prominent involvement of GABA and neuropeptides, shows striking similarities to the organization of the suprachiasmatic nucleus, the circadian clock of the mammalian brain.

Adjustability of the circadian clock in the cockroaches: a comparative study of two closely related species, Blattella germanica and Blattella bisignata.

A single 2h light pulse (250 lux) was given at various times to phase shift the locomotor circadian rhythm of two species of closely related cockroaches, Blattella bisignata and Blatella germanica. The phase-response curve (PRC) of both species showed a similar pattern. Phase delays and advances were induced by light pulse during the early and late subjective night, respectively, while no clear phase shifting was elicited during the subjective day. However, the magnitude of the phase delay (1.89h +/- 0.66h) and advance (0.69h +/- 0.36h) of B. bisignata was significantly larger than that of B. germanica (0.78h +/- 0.38h and 0.35h +/- 0.18h, respectively). This result indicates the superior adjustability of the circadian clock in B. bisignata. The period-response curve (PdRC) was also constructed for both species. Although both species did not show great flexibility in circadian period changes, the phase shifts were significantly correlated with the period changes in the advance zone of B. bisignata (r = 0.72, P < .1). This allowed the circadian clock of B. bisignata to display better entrainability since the phase advance adjustment was significantly more difficult than that of phase delay. The results indicate the overall adjustability of the circadian clock of B. germanica is inferior to that of B. bisignata. The significance of this finding is discussed from an ecological perspective.

Arthromitus (Bacillus cereus) symbionts in the cockroach Blaberus giganteus: dietary influences on bacterial development and population density.

The filamentous spore-forming bacterium Arthromitus, discovered in termites, millipedes, sow bugs and other soil-dwelling arthropods by Leidy (1850), is the intestinal stage of Bacillus cereus. We extend the range of Arthromitus habitats to include the hindgut of Blaberus giganteus, the large tropical American cockroach. The occurrence and morphology of the intestinal form of the bacillus were compared in individual cockroaches (n=24) placed on four different diet regimes: diurnally maintained insects fed (1) dog food, (2) soy protein only, (3)purified cellulose only, and (4) a dog food-fed group maintained in continuous darkness. Food quality exerted strong influence on population densities and developmental stages of the filamentous bacterium and on fecal pellet composition. The most dramatic rise in Arthromitus populations, defined as the spore-forming filament intestinal stage, occurred in adult cockroaches kept in the dark on a dog food diet. Limited intake of cellulose or protein alone reduced both the frequency of Arthromitus filaments and the rate of weight gain of the insects. Spores isolated from termites, sow bugs, cockroaches and moths, grown on various hard surfaces display a branching mobility and resistance to antibiotics characteristic to group I Bacilli whose members include B. cereus, B. circulans, B. alvei and B. macerans. DNA isolated from pure cultures of these bacilli taken from the guts of Blaberus giganteus (cockroach), Junonia coenia (moth), Porcellio scaber (sow bug) and Cryptotermes brevis (termite) and subjected to Southern hybridization with a 23S-5S B. subtilis ribosomal sequence probe verified that they are indistinguishable from laboratory strains of Bacillus cereus.

Altered behavior in two species of blattid cockroaches infected with Moniliformis moniliformis (Acanthocephala).

Moniliformis moniliformis-infected Periplaneta australasiae and Blatta orientalis were less active than uninfected controls in behavioral arena tests under both red and white light regimes. There was a strong interaction between light regime and parasitism for substrate use by P. australasiae. Under red light, parasitism decreased the use of black horizontal surfaces, whereas under white light, parasitism increased the use of black horizontal surfaces. In contrast, B. orientalis substrate use was unaffected by parasitism, although infected animals were less active than uninfected conspecifics under both light regimes. For both species, parasitism did not change the percentage of time spent in light, the freeze time, or the directional response to light.

Changes in pheromone production, release, mating behaviour and reproductive ability of the gamma-irradiated cockroach Nauphoeta cinerea (Olivier).

Mature males of Nauphoeta cinerea produce a sex pheromone 'seducin' which has short-range effects in attracting mature females of the same species. Exposure of newly-emerged adult males to 3.5, 7, 14 or 21 krad of gamma-radiation decreased their life expectancy and affected their mating behaviour. Bioassay of dichloromethane extracts of males showed that radiation doses (14 krad) sufficient to induce sterility did not affect the ability to produce pheromone but significantly reduced the release of pheromone by inhibiting wing-raising. The sterile-male technique using males sterilized by ionizing radiation in air may not be the method of choice for control of Nauphoeta cinerea.

[Hymenolepis nana var. fraterna (Cestoda: Hymenolepididae) in Leucophaea maderae (Dictyoptera: Blattidae): the host-parasite conflict after experimental inhibition of haemocytic reaction (author's transl)]. / Hymenolepis nana var. fraterna (Cestoda: Hymenolepididae) chez Leucophaea maderae (Dictyoptera: Blattidae): l'expression du conflit hôte-parasite après inhibition expérimentale de la réaction hémocytaire.

Development of non-encapsulated cysticercoids of Hymenolepis nana var. fraterna, in the haemocoele of Leucophaea maderae occured after the inhibition of the haemocytic reaction by irradiation or injection of a soluble antigen of Hymenolepis nana. Fine structure of the tegument of free larvae is observed and the mechanism of a possible defence of the parasite by the microvillar coat, discussed.

[Genetic control of Blattella germanica]. / Genetische Bekämpfung von Blattella Germanica.

Based on a literature survey, the possibilities of a genetic control of the German cockroach (Blattella germanica) are shown. First, an oversight is given on the cytogenetics of the German cockroach, including some important mutations. Then the control methods by genetic mechanisms are explained. This chapter begins with analysing the relevant biological pecularities. In control measures, the dominant lethal mutations (induced by rays rich with energy and by chemosterilants) have only a chance if they can be applied in the scope of autosterilization of natural populations. Reciprocal translocations may expect maximum consideration in the future of the control of the German cockroach. Some of these are already available in the heterozygote state. But the establishment of homozygous strains was not yet successful up to now. The possibilities of the application of translocation-heterozygotes are discussed. Such mutant strains of cockroaches which bear several translocations in the heterozygous state, offer the most promising way of control. This may even include the population's eradication. A long-lasting regulation of the population may be achieved with the introduction of insects mutated in this manner even in the case if a complete eradication is not attainable. It might be expected that also other genetic mechanisms may contribute, in future, to the improvement of cockroach control. Such mechanisms may be conditional lethal factors, sex distortions, and others more.