The effects of boric acid-induced oxidative stress on antioxidant enzymes and survivorship in Galleria mellonella

Larvae of the wax moth, Galleria mellonella (L.), were reared from first instar on a diet supplemented with 156, 620, 1,250, or 2,500 ppm boric acid (BA). The content of malondialdehyde (MDA, an oxidative stress indicator), and activities of the antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione peroxidase (GPx)] were determined in the fat body and hemolymph in the 7th instar larvae and newly emerged pupae. Relative to control larvae, MDA was significantly increased in larval hemolymph, larval and pupal fat body, but decreased in the pupal hemolymph. Insects reared on diets with 156- and 620-ppm BA doses yielded increased SOD activity but 1,250- and 2,500-ppm doses resulted in decreased SOD activity in larval hemolymph. SOD activity was significantly increased but CAT was decreased in the larval fat body. High dietary BA treatments led to significantly decreased GST activity. However, they increased GPx activity in larval hemolymph. Dietary BA also affected larval survival. The 1,250- and 2,500-ppm concentrations led to significantly increased larval and pupal mortality and prolonged development. In contrast, the lowest BA concentration increased longevity and shortened development. We infer that BA toxicity is related, at least in part, to oxidative stress management.     

THE EFFECTS OF XANTHOTOXIN ON THE BIOLOGY AND BIOCHEMISTRY OF Galleria mellonella L. (LEPIDOPTERA: PYRALIDAE)

The effects of a dietary plant allelochemical, xanthotoxin (XA), on survivorship, development, male and female adult longevity, fecundity, and hatchability of the greater wax moth Galleria mellonella L. were investigated. Oxidative stress indicators, the lipid peroxidation product, malondialdehyde (MDA), and protein oxidation products, protein carbonyl (PCO) contents, and activities of a detoxification enzyme glutathione S‐transferase (GST) activity were determined in wax moth adults. The insect was reared from first‐instar larvae on an artificial diets containing XA at 0.001, 0.005, or 0.1% to adult stage in laboratory conditions. Relative to the controls, the diets containing XA concentrations led to decreased survivorship in seventh instar, pupal, and adult stages. Compared to control diet (77.7%), the highest dietary XA concentration decreased survivorship to adulthood to 11.0%. The highest XA concentration (0.1%) reduced female longevity from 10.4 to 5.7 days and decreased egg numbers from 95.0 to 33.5 and hatchability from 82.7 to 35.6%. The lowest XA concentration (0.001%) led to about a sixfold increase in MDA content. XA at high concentrations (0.005 and 0.1%) increased MDA (by threefold) and protein carbonyl (by twofold) contents decreased GST activity. The highest dietary XA concentration decreased GST activity from 0.28 ± 0.025 to 0.16 ± 0.005 μmol/mg protein/min. We infer from these findings that XA‐induced oxidative stress led to decreased biological fitness.     

POTATO LEAF EXTRACT AND ITS COMPONENT, α‐SOLANINE,EXERT SIMILAR IMPACTS ON DEVELOPMENT AND OXIDATIVE STRESS IN Galleria mellonella L.

Plants synthesize a broad range of secondary metabolites that act as natural defenses against plant pathogens and herbivores. Among these, potato plants produce glycoalkaloids (GAs). In this study, we analyzed the effects of the dried extract of fresh potato leaves (EPL) on the biological parameters of the lepidopteran, Galleria mellonella (L.) and compared its activity to one of the main EPL components, the GA α‐solanine. Wax moth larvae were reared from first instar on a diet supplemented with three concentrations of EPL or α‐solanine. Both EPL and α‐solanine affected survivorship, fecundity, and fertility of G. mellonella to approximately the same extent. We evaluated the effect of EPL and α‐solanine on oxidative stress in midgut and fat body by measuring malondialdehyde (MDA) and protein carbonyl (PCO) contents, both biomarkers of oxidative damage. We evaluated glutathione S‐transferase (GST) activity, a detoxifying enzyme acting in prevention of oxidative damage. EPL and α‐solanine altered MDA and PCO concentrations and GST activity in fat body and midgut. We infer that the influence of EPL on G. mellonella is not enhanced by synergistic effects of the totality of potato leaf components compared to α‐solanine alone.     

Biological and immune response of Galleria mellonella (Lepidoptera: Pyralidae) to sodium tetraborate

Inorganic insecticides are commonly used in urban pest management because of their low mammalian toxicity. We tested the effects of sodium tetraborate (ST) on life parameters of greater wax moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae), to determine its sublethal toxicity on the insect. Survival, development, adult longevity, and fecundity of the wax moth were investigated by rearing larvae on artificial diets containing ST at concentrations of 0.005, 0.1, 0.2, or 0.3%. Larvae reared on medium at the highest concentration of ST (0.3%) had significantly decreased survival to the seventh instar and prolonged time required to reach the seventh instar. This concentration reduced pupa and adult yields to 12.5%, and it also prolonged development by 5 d. ST did not significantly influence adult longevity. Dietary ST led to significant decreases in fecundity and egg viability. Oviposition of survivors at the highest ST concentration (0.3%) was completely inhibited. Lysozyme content was decreased in larval hemolymph and fat body at high dietary ST concentrations. Fat body lysozyme content was significantly increased two-fold for larvae reared on diet at the lowest concentration of ST (0.005%). However, the highest concentration (0.3%) dramatically decreased fat body lysozyme content from 0.12 +/- 0.013 to 0.006 +/- 0.003 mg/ml in seventh instars. We infer that sublethal levels of dietary ST substantially influence life history parameters and immunocompetence in G. mellonella.     

Quercetin attenuates lindane induced oxidative stress in wistar rats

A wide number of pesticides, including highly persistent organochlorine compounds, such as lindane (γ-Hexachlorocyclohexane), have deteriorative effect on fauna and flora by inducing oxidative stress. Lindane induces cell damage by producing free radicals and reactive oxygen species. Quercetin, a dietary flavonoid, is ubiquitous in fruits and vegetables and plays an important role in human health by virtue of its antioxidant function. In this study the flavonoid quercetin was used to investigate its antioxidative effect against lindane induced oxidative stress in rats. The level of lipid peroxidation, reduced glutathione (GSH) were analysed in addition to the antioxidant enzymes such as catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD) and glutathione-s-transferase (GST) activities in the liver and kidney tissue. Levels of hepatic marker enzymes in serum like Aspartate transaminase (AST), Alanine transaminase (ALT), Alkaline phosphatase (ALP) and Lactate dehydrogenase (LDH) and renal markers like serum creatinine and serum urea were estimated. Administration of Lindane induced histopathological alterations and increased levels of serum hepatic and renal markers and malondialdehyde (MDA) with a significant decrease in GSH content and CAT, SOD, GPx and GST activities. Cotreatment of quercetin along with lindane significantly decreased the lindane induced alteration in histology, serum hepatic and renal markers and MDA and also improved the cellular antioxidant status. The results show that Quercetin ameliorates Lindane induced oxidative stress in liver and kidney. The quercetin exhibited chemopreventive effect when administered along with lindane.     

Effect of the Host Plant on the Antioxidative Defence in the Midgut of Lymantria dispar L. Caterpillars of Different Population Origins

THE RESPONSES OF GYPSY MOTH LARVAE ORIGINATING FROM TWO POPULATIONS (OAK FOREST, LOCUST FOREST) TO FAVORABLE (OAK) AND UNFAVORABLE (LOCUST) HOST PLANTS WERE MONITORED AT THE LEVEL OF MIDGUT ANTIOXIDATIVE DEFENCE: the activities of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase like ('GSH-Px like') and glutathione content (GSH). Short-term change of the diet (3 days) to locust leaves of the 5th instar larvae (oak population) provoked an increase in GST and 'GSH-Px like' activities as well as in the amount of GSH. On the contrary, transferring the gypsy moth larvae (locust population) to oak leaves was followed by a decrease in GST, 'GSH-Px like' activities, and in the amount of GSH. Feeding gypsy moth larvae from hatching on an unfavorable host plant such as locust, led to increases in GST and SOD activities and GSH content, as well as to a decrease in CAT activity in all instars studied (4th, 5th, 6th). The locust leaf diet caused changes in other components of antioxidative defence dependent on larval instar and population origin, a feature which could be ascribed to trophic adaptation of the gypsy moth to an unfavorable host plant.     

Ultraviolet light-induced oxidative stress: Effects on antioxidant response of Helicoverpa armigera adults

Ultraviolet (UV) light (blacklight), which emits UV in the range of 320-400 nm, has been used worldwide in light trapping of insect pests. In this article, we test the hypothesis that one of the effects of UV light irradiation is to increase oxidative stress on insects. The effects of UV light irradiation on total antioxidant capacity, malondialdehyde (MDA) and protein carbonyl contents and the activities of superoxide dismutase (SOD), catalase (CAT), peroxidases (POX) and glutathione-S-transferase (GST) were investigated in Helicoverpa armigera adults. The adults were exposed to UV light for various time periods (0, 30, 60 and 90 min). We found that exposure to UV light for 30 min resulted in increased total antioxidant capacity, protein carbonyl content and activities of SOD, CAT, POX and GST. When the exposure time lasted for 60 and 90 min, the protein carbonyl content and activities of CAT and GST remained significantly higher than the control. However, the antioxidant capacity and SOD activity returned to control levels, and POX activity decreased at 60 and 90 min. Our results confirm the hypothesis that UV light irradiation increases the level of oxidative stress in H. armigera adults.     

Induction of oxidative stress and DNA damage in cervix in acute treatment with benzo[a]pyrene

Benzo[a]pyrene [B(a)P] is one of the most prevalent environmental carcinogens and genotoxic agents. However, the mechanisms of B(a)P-induced oxidative damage in cervical tissue are still not clear. The present study was to investigate the oxidative stress and DNA damage in cervix of ICR female mice induced by acute treatment with B(a)P. Oxidative stress was assayed by analysis of malondialdehyde (MDA), superoxide anion and H(2)O(2), and antioxidant enzymes. The alkaline single-cell electrophoresis (SCGE) was used to measure DNA damage. The contents of MDA and glutathione (GSH), and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) were significantly increased in cervix 24, 48 and 72h after B(a)P treatment of a single dose of 12.5 and 25mg/kg, while GSH, CAT, SOD and GST had no significant difference with the dose of 50mg/kg B(a)P at post-treatment time 48 and 72h except for SOD activity at 48h which was significant. The maximum values of SOD, CAT, GST and GSH were peaked at 24h and then decreased gradually while GPx activities and MDA levels persisted for up to 72h. Superoxide anion, H(2)O(2) and DNA damage changed similarly as the activity of SOD, CAT or GST. Additionally, increases of formamidopyrimidine DNA glycosylase (FPG) specific DNA damage were observed and can be greatly rescued by vitamin C pretreatment. Overall, B(a)P demonstrated a time- and dose- related oxidative stress and DNA damage in cervix.     

Specific developmental window for establishment of an insect-microbe gut symbiosis

The alydid stinkbug Riptortus pedestris is specifically associated with a beneficial Burkholderia symbiont in the midgut crypts. Exceptional among insect-microbe mutualistic associations, the Burkholderia symbiont is not vertically transmitted but orally acquired by nymphal insects from the environment every generation. Here we experimentally investigated the process of symbiont acquisition during the nymphal development of R. pedestris. In a field population, many 2nd instar nymphs were Burkholderia free, while all 3rd, 4th, and 5th instar nymphs were infected. When reared on soil-grown potted soybean plants, Burkholderia acquisition occurred at a drastically higher frequency in the 2nd instar than in the other instars. Oral administration of cultured Burkholderia cells showed that 2nd and 3rd instar nymphs are significantly more susceptible to the symbiont infection than 1st, 4th, and 5th instar nymphs. Histological observations revealed rudimentary midgut crypts in the 1st instar, in contrast to well-developed midgut crypts in the 2nd and later instars. These results indicate that R. pedestris acquires the Burkholderia symbiont from the environment mainly during the 2nd instar period and strongly suggest that the competence for the symbiont infection is developmentally regulated by the host side. Potential mechanisms involved in infection competence and possible reasons why the infection preferentially occurs in the 2nd instar are discussed.     

Antioxidant mechanisms of the Nereidid Laeonereis acuta (Anelida: Polychaeta) to cope with environmental hydrogen peroxide

Hydrogen peroxide (H(2)O(2)) is a naturally occurring prooxidant molecule, and its effects in the macroinvertebrate infauna were previously observed. The existence of a gradient of antioxidant enzymes activity (catalase [CAT], glutathione peroxidase [GPx], superoxide dismutase [SOD], and glutathione-S-transferase [GST]) and/or oxidative damage along the body of the estuarine polychaeta Laeonereis acuta (Polychaeta, Nereididae) was analyzed after exposure to H(2)O(2). Because this species secretes conspicuous amounts of mucus, its capability in degrading H(2)O(2) was studied. The results suggest that L. acuta deal with the generation of oxidative stress with different strategies along the body. In the posterior region, higher CAT and SOD activities ensure the degradation of inductors of lipid peroxidation such as H(2)O(2) and superoxide anion (O(2)(.-)). The higher GST activity in anterior region aids to conjugate lipid peroxides products. In the middle region, the lack of high CAT, SOD, or GST activities correlates with the higher lipid hydroperoxide levels found after H(2)O(2) exposure. Ten days of exposure to H(2)O(2) also induced oxidative stress (lipid peroxidation and DNA damage) in the whole animal paralleled by a lack of CAT induction. The mucus production contributes substantially to H(2)O(2) degradation, suggesting that bacteria that grow in this secretion provide this capability.     

Changes of the Antioxidant Status and System of Generation of Free Radicals in Hemolymph of Galleria mellonella Larvae at Microsporidiosis

Changes of superoxide dismutase (SOD) and glutathione-S-transferase (GST) activities as well as of the content of SH-containing compounds were revealed in hemolymph of the native and the Vairimorpha ephestiae microsporidian-infected greater wax moth Galleria mellonella larvae. The SOD and GST activities in hemolymph of infected insects decreased at the stage of merogony, whereas during massive sporulation the enzymatic antioxidant activity in host tissues was higher than in control. By the ESR spectroscopy method, using the 1-hydroxy-3-carboxy-pyrrolidinespin-trap, generation of free radicals in hemolymph of infected insects was shown to decrease only at the stage of sporogony. The phenoloxidase activity in lymph was lower at acute microsporidiosis than in native larvae. The hemolymph concentration of thiol-containing proteins in infected insects did not differ from that in control. We suggest that decrease of generation of free radicals in hemolymph of the greater wax moth larvae at the stage of sporogony is due to a suppression of the prophenoloxidase system and an elevation of the antioxidant activity.     

Antioxidant responses of citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae), exposed to thermal stress

Relatively low or high temperatures are responsible for a variety of physiological stress responses in insects and mites. Induced thermal stress was recently associated with increased reactive oxygen species (ROS) generation, which caused oxidative damage. In this study, we examined the time-related effect of the relatively low (0, 5, 10, and 15 °C) or high (32, 35, 38, and 41 °C) temperatures on the activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidases (POX), and glutathione-S-transferase (GST), and the total antioxidant capacity (TEAC) of the citrus red mite, Panonychus citri (McGregor). The malondialdehyde (MDA) concentration, as a marker of lipid peroxidation in organisms, was also measured in the citrus red mite under thermal stress conditions. Results showed that SOD and GST activities were significantly increased and play an important role in the process of antioxidant response to thermal stress. Lipid peroxidation levels increased significantly (P < 0.001) and changed in a time-dependent manner. CAT and POX activity, as well as TEAC, did not vary significantly and play a minor role to remove the ROS generation. These results suggest that thermal stress leads to oxidative stress and antioxidant enzymes play an important role in reducing oxidative damage in the citrus red mite.     

Biochemical stress indicators of greater wax moth exposure to organophosphorus insecticides

Although acetylcholinesterase (AChE) is the primary target of organophosphorus insecticides (OPs), increasing evidence regarding their secondary effects suggests that OPs disturb homeostasis of insects by generating free radical intermediates that trigger lipid peroxidation. We therefore investigated alterations in lipid peroxidation product, malondialdehyde (MDA) content, and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, in conjunction with AChE activity as biochemical stress indicators in greater wax moth, Galleria mellonella (L.) larvae for OPs methyl parathion (MP) and ethyl parathion (EP). The effects of MP and EP were first investigated by rearing the young larvae on an artificial diet containing 0.01, 0.1, 1, 10, and 100 ppm of each insecticide. Second, the mature larvae were injected with 0.05, 0.5, 5, 50, and 500 ng of insecticides for determining the changes in biochemical stress responses. The diet with lowest level of MP significantly decreased the activities of all measured enzymes, whereas it increased MDA content. However ALT and AST were significantly higher in the larvae reared with the diet with high levels of MP than in control larvae. All tested levels of MP resulted in a decrease in AChE activity. The lowest level of EP in diet (0.01 ppm) significantly increased ALT activity, whereas it reduced that of AChE. This insecticide at 0.1 ppm resulted in reduced AST activity, but 1 ppm in diet elevated AST activity and MDA content. EP at 0.1 ppm and higher levels in the diet reduced ALT activity. All dietary EP levels significantly decreased AChE activity. ALT, AST, and AChE were lower in larvae fed with the diet containing 100 ppm ethyl parathion compared with larvae on control diet. MP at 50 ng per larva increased ALT and AST activities from 35.42 +/- 0.74 and 26.34 +/- 0.83 to 203.57 +/- 1.09, and 122.90 +/- 1.21 U/g, respectively, when the mature larvae were injected. All injected doses of EP dramatically reduced both ALT and AST activities, but only the lowest and highest levels of this insecticide decreased AChE activity. The lowest level of this insecticide also significantly increased MDA content in larvae. High levels of both insecticides increased MDA content. We observed a significant higher increase in MDA content in the larvae reared with 10 ppm EP (102.16 +/- 1.57 nmol/g protein) than the control group (30.28 +/- 1.42 nmol/g protein). These results suggest that OPs caused the metabolic and synaptic dysfunctions in greater wax moth and alter its biochemical physiology in response to oxidative stress.     

蚯蚓提取物对家蚕中肠氧化损伤、总抗氧化能力及抗氧化酶含量的影响

【目的】研究蚯蚓提取物对家蚕Bombyx mori中肠组织氧化应激及抗氧化酶含量的影响,探究蚯蚓提取物的抗氧化功能。【方法】分别给家蚕5龄幼虫饲喂蚯蚓(赤子爱胜蚓Eisenia foetida)提取液原液的50, 100和200倍稀释液处理后的桑叶,测定处理6 d后家蚕中肠组织中氧化损伤产物丙二醛(MDA)和乳酸脱氢酶(LDH)的含量;利用qRT-PCR检测家蚕中肠组织中抗氧化酶关键基因(Cat,Sod和GSH-Px)的mRNA表达水平;同时采用ELISA法检测中肠组织中抗氧化酶[过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)]含量及总抗氧化能力(T-AOC)。【结果】与对照组相比,50, 100和200倍稀释组家蚕中肠组织中MDA, CAT, SOD和GSH-Px含量及T-AOC均差异不显著,200倍稀释组LDH含量显著降低了9.85%,100倍稀释组中肠中Cat和GSH-Px的表达量均显著高于对照组,3个稀释组中Sod的表达量均显著高于对照组。【结论】添食蚯蚓提取物可通过降低家蚕中肠LDH含量、提高抗氧化酶基因的表达水平进而提高家蚕的抗氧化能力。     

Hepatoprotective and Antioxidant Activity of Linden (Tilia platyphyllos L.) Infusion Against Ethanol-Induced Oxidative Stress in Rats

The present study was carried out to evaluate the hepatoprotective effect and antioxidant role of infusion prepared from linden flowers (LF) against ethanol-induced oxidative stress. The hepatoprotective and antioxidant role of the plant’s infusion against ethanol-induced oxidative stress was evaluated by measuring liver damage serum biomarkers, aspartate aminotransferase (AST), alanine aminotransferase, lactate dehydrogenase (LDH), total protein, total albumin, and total cholesterol level; ADS such as GSH, GR, SOD, GST, CAT and GPx, and MDA contents in various tissues of rats. Rats were divided into four experimental groups: I (control), II (20 % ethanol), III (2 % LF), and IV (20 % ethanol + 2 % LF). According to the results, the level of serum marker enzymes, AST and LDH, was significantly increased in group alcohol and group LF as compared to control group, whereas decreased in group IV as compared to ethanol group. With regard to MDA content and ADS constituents, MDA contents of alcohol group in all tissues, except for erythrocytes and heart, and in brain, kidney, and spleen of LF group significantly increased compared to control group, whereas LF beverage extract supplementation did not restore the increased MDA towards close the control level. In addition, while ethanol caused fluctuation in antioxidant defense system constituents level as a result of oxidative stress condition in the rats, it could have not been determined the healing effects of the LF against these fluctuations. The results indicated that LF beverage extract could not be as important as diet-derived antioxidants in preventing oxidative damage in the tissues by reducing the lipid oxidation or inhibiting the production of ethanol-induced free radicals in rats.     

Effect of bacterial infection on antioxidant activity and lipid peroxidation in the midgut of Galleria mellonella L. larvae (Lepidoptera, Pyralidae)

Bacillus thuringiensis is one of the most widely used sources of biorational pesticides, as well as a key source of genes for transgenic expression to provide pest resistance in plants. In this study the effect of Bacillus thuringiensis ssp. galleriae (Bt) infection on the activity of superoxide dismutase (SOD), glutathione S-transferase (GST), catalase (CAT), concentrations of oxidated and reduced thiols (RSSR/RSH) and malondialdehyde (MDA) was tested in the midgut of Galleria mellonella larvae. We found that Bt infection resulted in increased activities of SOD, GST, malondialdehyde and RSSR/RSH ratio the first day after inoculation. However, catalase activity decreased on the first and following days after bacterial infection by Bt. Our results confirm the hypothesis that Bt infection increases the level of oxidative stress in the larval midgut. In light of this study, it seems possible that oxidative damage contributes to cell death in the midgut during bacteriosis.     

Boric acid-induced effects on protein profiles of Galleria mellonella hemolymph and fat body

The dietary effects of boric acid (BA) on the protein profiles of greater wax moth, Galleria mellonella (L.), were investigated in hemolymph and fat body of final instar (VIIth) and pupae. The insects were reared from first-instar larvae on an artificial diets containing 156, 620, 1250 or 2500 ppm of BA. We detected many undetermined protein fractions (6.5-260 kDa) in addition to well-defined protein fractions such as lipophorins and storage proteins in the tissues by using sodium dodecyl-sulphate polyacrylamide gradient gel electrophoresis. A marked quantitative change in the 45 kDa protein fraction of the hemolymph was observed in the VIIth instar larvae reared on 2500 ppm dietary BA.     

氧化损伤是热胁迫下小金蝠蛾幼虫不能存活的重要原因

【目的】小金蝠蛾Thitarodes xiaojinensis是冬虫夏草菌Ophiocordyceps sinensis的寄主昆虫,生活于高海拔、高寒地区,低温适应性强,但在室温下（25~27℃）不能正常存活。本研究检测了热胁迫（27℃）对小金蝠蛾幼虫消化酶及抗氧化系统的影响,以期揭示小金蝠蛾室温不耐受的生理机制。【方法】小金蝠蛾8龄幼虫分两组进行处理：高温组于27℃下饲养,对照组于16℃下饲养。处理24 h后观察虫体状态,并解剖,取中肠及血淋巴。透射电镜观察中肠细胞线粒体结构,分别测定中肠总蛋白酶和糖基水解酶活性,血淋巴丙二醛（MDA）含量,以及血淋巴保护酶系中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）的活性。【结果】两组幼虫中肠总蛋白酶及糖基水解酶活性均随反应温度（16~37℃）升高而增强。协方差分析显示,高温组幼虫酶活性极显著低于对照组（P<0.01）。然而,高温组幼虫在27℃下的酶活性与对照组幼虫在16℃下的酶活性无显著差异（P<0.05）。热胁迫下虫体血淋巴中丙二醛含量显著升高（P<0.05）,提示出现了氧化损伤。透射电镜结果显示,高温组中肠细胞线粒体肿胀,膜受损,嵴排列混乱,结构破坏。对活性氧起清除作用的3种保护酶中,仅POD活性显著升高（P<0.05）,SOD和CAT活性均无显著变化（P>0.05）。【结论】消化酶活性的变化可能不是小金蝠蛾室温不耐受的重要因素;氧化损伤是其热胁迫下不能正常存活的一个重要原因。     

Antioxidant responses of the pest natural enemy Hylyphantes graminicola (Araneae: Linyphiidae) exposed to short-term heat stress

Temperature is a critical abiotic factor that causes physiological changes in arthropods. However, little is known about the effect of heat stress on the antioxidant responses of Araneae species. Hylyphantes graminicola is a dominant predator in many cropping systems in China. In the present study, the effect of short-term heat stress (36, 38, 40 or 42 °C) on the reactive oxygen species (ROS) levels, the activities of antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], peroxidases [POD] and glutathione-S-transferases GST]), total antioxidant capacity (TAC), malondialdehyde (MDA) concentrations and survival of H. graminicola spiderlings and adults were investigated. The results showed that H. graminicola adults had a significantly higher survival rate compared to spiderlings at 40 °C. The heat stress increased ROS contents in H. graminicola. The SOD, CAT, POD and GST activities increased in spiderlings and adults under heat stress. These data suggest a defensive function for these enzymes in alleviating oxidative damage. Specifically, SOD plays a key role in reducing the high level of superoxide radicals in spiderlings and adults. Moreover, the POD and CAT capabilities for scavenging H₂O₂ in spiderlings were similar, and CAT may play a more important role than POD in scavenging H₂O₂ in adults at 42 °C. The spiderling TAC increased significantly at 40 and 42 °C, and the adult TAC was stable at 36–40 °C but decreased at 42 °C. These data suggest that TAC was insufficient in H. graminicola adults under more severe stress conditions. These results further our understanding of the physiological response of Araneae species exposed to heat stress.     

Antioxidant responses of Propylaea japonica (Coleoptera: Coccinellidae) exposed to high temperature stress

Temperature is one of the most important environmental factors, and is responsible for a variety of physiological stress responses in organisms. Induced thermal stress is associated with elevated reactive oxygen species (ROS) generation leading to oxidative damage. The ladybeetle, Propylaea japonica (Thunberg) (Coleoptera: Coccinellidae), is considered a successful natural enemy because of its tolerance to high temperatures in arid and semi-arid areas in China. In this study, we investigated the effect of high temperatures (35, 37, 39, 41 and 43 °C) on the survival and activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidases (POD), glutathione-S-transferases (GST), and total antioxidant capacity (TAC) as well as malondialdehyde (MDA) concentrations in P. japonica adults. The results indicated that P. japonica adults could not survive at 43 °C. CAT, GST and TAC were significantly increased when compared to the control (25 °C), and this played an important role in the process of antioxidant response to thermal stress. SOD and POD activity, as well as MDA, did not differ significantly at 35 and 37 °C compared to the control; however, there were increased levels of SOD, POD and MDA when the temperature was above 37 °C. These results suggest that thermal stress leads to oxidative stress and antioxidant enzymes play important roles in reducing oxidative damage in P. japonica adults. This study represents the first comprehensive report on the antioxidant defense system in predaceous coccinellids (the third trophic level). The findings provide useful information for predicting population dynamics and understanding the potential for P. japonica as a natural enemy to control pest insects under varied environmental conditions.