Photoprotective egg pigmentation reduces negative carryover effects of ultraviolet radiation on stink bug nymph survival.

Solar ultraviolet radiation (UV) can have a wide range of negative effects on animal fitness that take place not only during, but also after exposure (carryover effects). UV-induced carryover effects and potential adaptations to avoid or mitigate them are understudied in terrestrial animals, including arthropods and their potentially most vulnerable life stages. The spined soldier bug, Podisus maculiventris, increases the emergence of its eggs that are exposed to UV radiation by coating them in sunscreen-like pigmentation, but consequences of these conditions of embryonic development for nymphs and adults are unknown. We measured stink bug nymph survival, adult size and sex ratio following exposure of differently pigmented eggs across a range of UV intensities. Nymph survival to adulthood decreased with higher intensity of embryonic UV exposure and this carryover effect decreased with higher level of egg pigmentation, similar to previously observed effects on embryonic survival. Nymph development time, adult size and sex ratio were not affected by embryonic exposure to UV radiation nor by photoprotective egg pigmentation. This study is the first to demonstrate the potential for lethal carryover effects of UV radiation in terrestrial insects, highlighting the need for more studies of how this pervasive environmental stressor can affect fitness across life stages.

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.

Developmental Phase-Specific Mortality After Ultraviolet-B Radiation Exposure in the Two-Spotted Spider Mite.

Exposure to ambient ultraviolet-B (UVB) radiation generates DNA lesions, such as cyclobutane pyrimidine dimers and 6-4 pyrimidine-pyrimidine photoproducts in Tetranychus urticae Koch (Acari: Tetranychidae). Larvae appeared normal and healthy after UVB irradiation. Conversely, many mites were trapped in their old epidermis or experienced retarded development and shrunk, thus failing to molt from protochrysalises to protonymphs and died. This suggested that DNA lesions per se were not causing lethality in mites unless damaged genes were expressed. UVB-induced DNA lesions may have interfered with DNA replication and gene expression during the physiological changes of morphogenesis in the chrysalis stage. Comprehensive gene expression analysis by RNA sequencing revealed that gene expression involving epidermal tissue (characteristically cuticular protein genes) and myosin heavy chain muscle-like genes were downregulated in protochrysalises irradiated with UVB at the larval stage. We conclude that the success of protochrysalis molting is determined by whether the DNA lesions of genes, particularly those connected with morphogenesis, are repaired before expression at the protochrysalis stage.

X-ray Irradiation Control of Frankliniella occidentalis and Frankliniella intonsa (Thysanoptera: Thripidae) in the Exportation of Freshly Cut Lily Flowers.

Lily (Lilium longiflorum Thunb.) is the most representative bulb flower, and it is the third most important flower in the flower industry of South Korea after rose and chrysanthemum. To determine the efficacy of X-ray irradiation for use in quarantine processing, two species of flower thrips (Frankliniella intonsa (Trybom) and Frankliniella occidentalis (Pergande)) were placed in the top, middle, and bottom locations of lily boxes and irradiated with different X-ray doses. After irradiation with an X-ray dose of 150 Gy, the egg hatching of the two flower thrips was completely inhibited at every location in the lily boxes, and the irradiated F. intonsa and F. occidentalis nymphs failed to emerge as adult in every location of the lily boxes. When the adults were irradiated at 150 Gy, the fecundity of the two flower thrips was markedly lower than that of the untreated control groups. The F1 generation failed to hatch at the top and middle locations, whereas the F1 generation of both F. intonsa and F. occidentalis was not suppressed at the bottom locations, even at 200 Gy. However, hatching was perfectly inhibited at 300 Gy of X-ray irradiation. Also, X-rays did not affect the postharvest physiology of cut lilies. Therefore, a minimum dose of 300 Gy is recommended for the control of F. intonsa and F. occidentalis for the exportation of lily.

Efficacy of Two Larvasonic™ Units Against Culex Larvae and Effects on Common Aquatic Nontarget Organisms in Harris County, Texas.

The Larvasonic™ Field Arm Mobile Wetlands Unit and SD-Mini were tested for efficacy against Culex larvae, and effects on aquatic nontarget organisms (NTO). The Field Arm provided 84.61% to 100% control of caged Culex larvae out to 0.91-m distance in shallow ditches and 60.45% control of Culex larvae at 0.61-m without any effects to caged NTO. Slow ditch treatment achieved 77.35% control compared to fast treatment (20.42%), whereas 77.65% control was obtained along edges of a neglected swimming pool, compared to near the middle (23.97%). In bucket tests, the SD-Mini provided >97% control of Culex and 85.35% reduction of immature giant water bugs, which decreased slightly (83.45%) over the monitoring period, which was not significantly different from cannibalistic damselflies (62.80%), with reduction of both being significantly higher than other NTO tested. There was a small (0.37%) reduction of dragonflies (naiads), due to cannibalism. Both Larvasonic units could effectively augment conventional larvicide operations in smaller areas without causing resistance within mosquito populations or harming NTO when used properly.

Diapause induction and termination in the small brown planthopper, Laodelphax striatellus (Hemiptera: Delphacidae).

The small brown planthopper, Laodelphax striatellus (Fallén) enters the photoperiodic induction of diapause as 3rd or 4th instar nymphs. The photoperiodic response curves in this planthopper showed a typical long-day response type with a critical daylength of approximately 11 h at 25 °C, 12 h at 22 and 20 °C and 12.5 h at 18 °C, and diapause induction was almost abrogated at 28 °C. The third stage was the most sensitive stage to photoperiod. The photoperiodic response curve at 20 °C showed a gradual decline in diapause incidence in ultra-long nights, and continuous darkness resulted in 100% development. The required number of days for a 50% response was distinctly different between the short- and long-night cycles, showing that the effect of one short night was equivalent to the effect of three long nights at 18 °C. The rearing day length of 12 h evoked a weaker intensity of diapause than did 10 and 11 h. The duration of diapause was significantly longer under the short daylength of 11 h than it was under the long daylength of 15 h. The optimal temperature for diapause termination was 26 and 28 °C. Chilling at 5 °C for different times did not shorten the duration of diapause but significantly lengthened it when chilling period was included. In autumn, 50% of the nymphs that hatched from late September to mid-October entered diapause in response to temperatures below 20 °C. The critical daylength in the field was between 12 h 10 min and 12 h 32 min (including twilight), which was nearly identical to the critical daylength of 12.5 h at 18 °C. In spring, overwintering nymphs began to emerge in early March-late March when the mean daily temperature rose to 10 °C or higher.

Embryonic diapause in the Australian plague locust relative to parental experience of cumulative photophase decline.

The Australian plague locust Chortoicetes terminifera (Walker) exhibits facultative embryonic diapause during autumn. To approximate natural photoperiod changes during late summer and autumn, locust nymphs were reared under different total declines in laboratory photophase (-0.5, -0.75, -1.0, -1.25, -1.5, -1.75, -2 h each lowered in 15 min steps) in a 24 h photoperiod to quantify any effect on the subsequent production of diapause eggs. Induction of diapause eggs was significantly affected by accumulated photoperiod decline experienced by the parental generation throughout all development stages from mid-instar nymph to fledgling adult. The incidence of embryonic diapause ranged from nil at -0.5 h to 86.6% diapause at -2 h. Continued declines in photoperiod for post-teneral locusts (transitioned from -1h until fledging to -1.75 h) produced a further increase in the proportion of diapause eggs. The results were unaffected by time spent at any given photoperiod, despite a previously indicated maximal inductive photoperiod of 13.5h being used as the mid-point of all treatments. Implications for the seasonal timing processes of photoperiodism in C. terminifera, which has a high migratory capacity and a latitudinal cline in the timing of diapause egg production across a broad geographic range, are discussed.

Functional analysis of the circadian clock gene period by RNA interference in nymphal crickets Gryllus bimaculatus.

The circadian clock gene period (Gryllus bimaculatus period, Gb'per) plays a core role in circadian rhythm generation in adults of the cricket Gryllus bimaculatus. We examined the role of Gb'per in nymphal crickets that show a diurnal rhythm rather than the nocturnal rhythm of the adults. As in the adult optic lobes, Gb'per mRNA levels in the head of the third instar nymphs showed daily cycling in light-dark cycles with a peak at mid night, and the rhythm persisted in constant darkness. Injection of Gb'per double-stranded RNA (dsRNA) into the abdomen of third instar nymphs knocked-down the mRNA levels to 25% of that in control animals. Most Gb'per dsRNA injected nymphs lost their circadian locomotor activity rhythm, while those injected with DsRed2 dsRNA as a negative control clearly maintained the rhythm. These results suggest that nymphs and adults share a common endogenous clock mechanism involving the clock gene Gb'per.

Irradiation as a phytosanitary treatment for Aspidiotus destructor (Homoptera: Diaspididae).

Coconut scale, Aspidiotus destructor Signoret (Homoptera: Diaspididae), is a quarantine pest of banana (Musa spp.) and many tropical crops. Irradiation was examined as a potential phytosanitary treatment to control coconut scale. Dose-response tests were conducted with second-stage nymphs, adult females without eggs, and adult females with eggs at a series of irradiation doses between 60 and 200 Gy to determine the most tolerant stage. The adult female with eggs was the most tolerant stage. In large-scale validation tests and dose-response tests, a total of 32,716 adult female scales with eggs irradiated with doses between 100 and 150 Gy produced no F1 adults with eggs. Irradiation treatment with a minimum absorbed dose of 150 Gy should provide quarantine security for coconut scale on exported commodities.

Irradiation as a phytosanitary treatment for white peach scale (Homoptera: Diaspididae).

Irradiation was examined as a potential phytosanitary treatment to control white peach scale, Pseudaulacaspis pentagona (Targioni-Tozzetti) (Homoptera: Diaspididae), a serious quarantine pest of papaya, Carica papaya L., in Hawaii. Dose-response tests were conducted with second-stage nymphs, adult females without eggs, and adult females with eggs at a series of irradiation doses between 60 and 150 Gy to determine the most tolerant stage. The adult female with eggs was the most tolerant stage. In large-scale validation tests 35,424 adult female scales with and without eggs irradiated at a dose of 150 Gy produced no F1 generation adults with eggs. Irradiation treatment with a minimum absorbed dose of 150 Gy should provide quarantine security for white peach scale on exported papaya and other commodities.

Nymphal survival and movement of crawlers of Bemisia argentifolii (Homoptera: Aleyrodidae) on leaf surfaces of selected vegetables.

Bemisia argentifolii Bellows & Perring generally feeds and develops on the under leaf surface of most host plants, but in excess of 50% of the immature population may be found on the upper surface of some host species. This study determined the influence of leaf surface on survival of immature B. argentifolii and the likelihood of movement by the crawler (1st instar) from the upper (adaxial) leaf surface on selected vegetable hosts. Laboratory, tests were conducted on 5 vegetables: cantaloupe, Cucumis melo L.; collard, Brassica oleracea ssp. acephala de Condolle: cowpea, Vigna unguiculata (L.) Walpers ssp. unguiculata; pepper, Capsicum annuum L. ssp. annuum; and tomato, Lycopersicon esculentum Miller. Survival to the 1st instar was high (85-95%) on the upper leaf surface on all hosts. Survival to the adult stage was similar between whitefly nymphs on the upper and lower leaf surfaces within each host crop, except more survived on the lower surface of cowpea compared with the upper surface. Movement of the crawlers from the upper to the lower surface was high on pepper (approximately 80%), cantaloupe (approximately 55%), and cowpea (approximately 55%). Conversely, less movement to the lower surface was observed on collard (approximately 18%) and tomato (approximately 30%). The impetus to move from the upper surface appears primarily a response to feeding and tactile cues instead of responses to geotropic or phototropic stimuli.

[The reaction of the tick Hyalomma asiaticum (Acarina, Ixodidae) to 1- to 4-GHz microwaves]. / Reaktsiia kleshscha Hyalomma asiaticum (Acarina, Ixodidae) na mikrovolny 1--4 GGts.

Low-energy microwave radiation in the frequency range in question was found to exert a noticeable biological action on H. asiaticum. Radiation delayed larval hatch by 3-20 days, increased the activity duration of newly moulted larvae by 17-24 days, reduces the survival of hungry larvae and nymphs by 4-10 days. The efficiency of the biological action of microwaves is enhanced by impairments in the natural developmental rhythm of the tick.

[The effect of UV rays on parasitic arthropods. 3. In vitro and in vivo studies of the effect of a fractionated UV irradiation on the development stages of Psoroptes cuniculi (Acaridida: Psoroptidae)]. / Einfluss von UV-Strahlen auf parasitische Arthropoden. 3. Mitteilung: Untersuchungen in vitro und in vivo über den Einfluss einer fraktionierten UV-Bestrahlung auf Entwicklungsstadien von Psoroptes cuniculi (Acaridida: Psoroptidae).

In vitro studies were conducted into Psoroptes (Ps.) cuniculi larvae and nymphs of undefined age and gender. 30 males and females were involved in each of the experiments. Evidence was found the life expectancy of mites exposed to daily UV irradiation for 1, 2, 3, 4 or 5 minutes was reduced with significance, as compared to non-irradiated mites or to those with only one irradiation of the same length. Developmental stages of Ps. cuniculi responded in differentiated ways to the same dose rate, when applied by one single extended or fractionated shorter irradiation. Fractionated irradiation was more often survived by females than one single extended irradiation, whereas earlier death occurred to larvae following exposure to fractionated irradiation. Mange mites were not eliminated from rabbits with moderate ear mange by fractionated locally delimited in vivo irradiation, up to 16 applications of 10 minutes each or 6 or 9 applications of 10, 20 or 40 minutes each, with one-week intervals in between. Ear mange was clinically re-manifested, after irradiations had been discontinued.

The subgenus Persicargas (Ixodoidea: Argasidae: Argas). 33. Effect of gamma radiation on first nymphal instar A. (P.) arboreus and adult fertility.

Gamma radiation doses higher than 1,000 rads are lethal to first nymphal instar Argas (Persicargas) arboreus. Only 50% of first nymphal instars receiving 1,000 rads reach adulthood but those receiving 100-500 rads survive normally. Males resulting from irradiated first nymphal instars are almost normally fertile. Female germinal cells tolerate higher radiation doses received in the first nymphal instar stage than in the adult stage. Females resulting from first nymphal instars receiving does higher than 100 rads are less fertile (egg number and percent hatch) than normal and produce F1 larvae of lower than normal viability. Progenies of females irradiated as nymphs apparently inherit lethal genes, which may be useful, if irradiated at critical stages, in tick control.

The time of determination of gynoparae and males in the bird cherry-oat aphid, Rhopalosiphum padi.

Apterous exules of Rhopalosiphum padi which experienced short photoperiods only during the first half of their nymphal life all produced gynoparae which made up 57% of the offspring produced in the first 7 days of the mother's reproductive life. Short photoperiods during the second half of a mother's nymphal life did not induce the production of gynoparae. However, when short photoperiods were experienced throughout a mother's nymphal life significantly more gynoparae (82%) were produced. Ten per cent of the offspring of mothers that experienced short photoperiods only during their adult life developed into gynoparae. Of the offspring reared in short photoperiods, but born to mothers reared and kept in long photoperiods, 30% developed into gynoparae. When mothers were exposed to short photoperiods in their adult life and their offspring so treated, then 90% of the offspring developed into gynoparae. Males only occurred amongst the last offspring of mothers that experienced short photoperiods in either the first or the second half of their nymphal life.