Tissue-specific responses of Lymantria dispar L. (Lepidoptera: Erebidae) larvae from unpolluted and polluted forests to thermal stress.

In this paper the effects of increased environmental temperature on the relative growth rate (RGR) and developmental time in 5th instar L. dispar larvae originating from unpolluted and polluted forests were analyzed. As indicators of the level of generated reactive oxygen species in thermal stress, we estimated midgut and hemolymph activity of the antioxidative enzymes, superoxide dismutase (SOD) and catalase (CAT), as well as the detoxifying enzymes glutathione S-transferase (GST), carboxylesterase (CaE) and acetylcholinesterase (AChE) from the midgut and brain tissue. We also examined the influence of induced thermotolerance as a species' ability to overcome the negative effects of this stressor. In larvae originating from the unpolluted forest, the midgut is the primary location of increased SOD and CAT activity and induced thermotolerance did not modified their activity in either tissue. In larvae from the polluted forest, in both tissues SOD activity was more sensitive to an increased temperature and induced thermotolerance than CAT. Carboxylesterase responded diversely to thermal stress depending on the analyzed tissue regardless the origin of larvae, while the activity of GST and AChE in tissue depended on the origin of larvae. Induced thermotolerance modified the activity of detoxifying enzymes in larvae originating from the polluted forest. Combining the selected parameters into an integrated biomarker response (IBR) the GST, CaE and AChE battery emerged as a potential biomarker for thermal stress in L. dispar larvae.

Glutathione S-transferase in the midgut tissue of gypsy moth (Lymantria dispar) caterpillars exposed to dietary cadmium.

Activity of glutathione S-transferase (GST) in midgut of gypsy moth caterpillars exposed to 10 and 30µg Cd/g dry food was examined. Based on the enzyme reaction through conjugation with glutathione, overall activity remained unaltered after acute and chronic treatment. No-observed-effect-concentration (10µg Cd/g dry food) significantly increased activity only after 3-day recovery following cadmium administration. Almost all comparisons of the indices of phenotypic plasticity revealed statistically significant differences. Despite the facts that GST has important role in xenobiotic biotransformation, our results indicate that this enzyme in insect midgut does not represent the key factor in cadmium detoxification.

Cadmium-induced changes of gypsy moth larval mass and protease activity.

Cadmium uptake takes place mainly through food. Lymantria dispar larvae were exposed to dietary cadmium in concentrations of 10 and 30µg Cd/g dry food (NOEC, no-observed-effect and LOEC, lowest-observed-effect concentration, respectively) for acute and chronic treatment and recovery. We established that metal contamination decreased mass only during the chronic treatment at 30µg Cd/dry food with no recovery on removal of cadmium for 3days. Significant reduction of protease activity was detected at LOEC after the acute and chronic treatments. Protease showed enhanced plasticity with regard to the fitness trait (mass) during environmental stress and the higher cadmium load, when it changed. The statistically significant higher index of phenotypic plasticity for protease correlated with lower variability. Protease isoforms at the same cadmium treatments differed between genotypes, while some protease isoforms from one egg-mass differed between cadmium treatments. Owing to the low sensitivity and plasticity of mass change during exposure to cadmium, as well as its small influence, we concluded that larval mass is not a good indicator of cadmium presence in food. We suggest that proteases, with further research, might be a suitable indicator of dietary cadmium contamination, as well as nutriment utilization during heavy metal stress.

Enzymatic biomarkers as indicators of dietary cadmium in gypsy moth caterpillars.

Heavy metals damage the structure, chemistry, and function of cells, including enzyme systems inside them. Variation in the profile of biochemical biomarkers in prevalent species should be used for assessing environmental contamination. The present study pays attention to the phosphatases present in the midgut of gypsy moth fourth instar caterpillars, which had been exposed to short- and long-term cadmium intake at 10 and 30 µg Cd/g dry food. Chronic cadmium ingestion significantly inhibited the activity of all examined phosphatases, while only the activity of lysosomal phosphatase was acutely decreased. Total acid phosphatase activity recovered from both long-term cadmium treatments within 3 days. The low index of phenotypic plasticity was connected to high variability of plasticity. Dependence of phosphatase isoforms on genotype and duration of cadmium treatment was determined. We concluded that, with further investigations, profiling of total acid phosphatase activity, as well as the lysosomal fraction can be used as a biomarker for acute sublethal metal toxicity.

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.

Changes in activity of non-specific esterases in cadmium treated Lymantria dispar larvae.

Many biochemical, physiological and histological criteria have been used as indicators of exposures and effects of the contaminants. These changes can indicate the response of an organism to a specific environmental stressor. In the present paper, the effect of the acute and chronic exposure to cadmium as well as recovery from two cadmium concentrations (10 and 30 µgCd/g dry food) on gypsy moth (Lymantria dispar) midgut esterases was investigated. The influence of cadmium on trait plasticity was also examined. Esterases showed great sensitivity to low metal concentrations during acute and chronic treatments. Their activities during short-term exposure and after recovery significantly depended on cadmium concentrations. The esterases had greater index of plasticity during chronic treatments with 10 and 30 µgCd/dry food. Five esterase isoforms between 64 and 250 kDa were detected. Isoforms of esterases exposed to any of the two cadmium effects differed among several egg-masses. Isozymes were distinguished in one egg-mass during different cadmium treatments. We conclude that these enzymes could be considered potential and sensitive non-selective biomarkers for the presence of cadmium in food.