Digestive enzyme activity and macromolecule content in the hemolymph of differentially adapted Lymantria dispar L. populations after short-term increases in ambient temperature

Global, unpredictable temperature increases have strong effects on all organisms, especially insects. Elucidating the effects of short-term temperature increases on midgut digestive enzymes (α-glucosidase, lipase, trypsin, and leucine aminopeptidase - LAP) and metabolic macromolecules in the hemolymph (proteins, lipids, and trehalose) of phytophagous pest larvae of Lymantria dispar is important for general considerations of insect adaptation to a warming climate and potential pest control options. We also wanted to determine whether the different adaptations of L. dispar populations to environmental pollution might affect their ability to cope with heat stress using larvae from the undisturbed, Kosmaj forest and disturbed, Lipovica forest. Heat treatments at 28 °C increased α-glucosidase activity in both larval populations, inhibited LAP activity in larvae from the polluted forest, and had no significant effect on trypsin and lipase activities, regardless of larval origin. The concentration of proteins, lipids, and trehalose in the hemolymph of larvae from the disturbed forest increased, whereas the population from the undisturbed forest showed only an increase in proteins and lipids after the heat treatments. Larval mass was also increased in larvae from the undisturbed forest. Our results suggest a higher sensitivity of digestive enzymes and metabolism to short-term heat stress in L. dispar populations adapted to pollution in their forest habitat, although climate warming is not beneficial even for populations from unpolluted forests. The digestive and metabolic processes of L. dispar larvae are substantially affected by sublethal short-term increases in ambient temperature.

Antioxidative enzymes, alkaline phosphatases and Hsp70 expression in larvae of Lymantria dispar (Lepidoptera: Erebidae) from unpolluted and polluted forests after chronic cadmium treatment

Long-term exposure of populations to pollution may result in enhanced ability to cope with environmental stress. To compare the responses of two Lymantria dispar populations living in unpolluted and polluted forests (UP and PP, respectively), we chronically exposed larvae to cadmium at concentrations of 50 and 100 μg Cd/g dry food (Cd1 and Cd2, respectively). We examined cadmium accumulation in the midgut and hemolymph, activities of superoxide dismutase (SOD), catalase (CAT), and alkaline phosphatases (ALP) in the midgut, as well as Hsp70 protein expression in the midgut, hemolymph, and brain and evaluated these parameters as biomarkers of cadmium contamination. Larvae from PP, fed a control diet, showed higher activity of SOD and increased Hsp70 expression compared with larvae from UP. Excessive amounts of Cd were accumulated in the midgut of all Cd-fed larvae, whereas Cd content in the hemolymph was elevated only in larvae from PP after Cd2 treatment. In larvae from UP, Cd2 treatment decreased the activity of CAT and induced the expression of Hsp70 in the midgut and hemolymph. In larvae from PP, exposure to both Cd concentrations strongly attenuated SOD and CAT activities, while Hsp70 expression was not induced in any organ/tissue. Cd did not affect ALP activity in either population. Midgut Cd content proved to be a suitable indicator of Cd contamination for both polluted and unpolluted habitats.

Effects of dietary fluoranthene on tissue-specific responses of carboxylesterases, acetylcholinesterase and heat shock protein 70 in two forest lepidopteran species

In this study, responses of carboxylesterases, acetylcholinesterase, and stress protein Hsp70 were examined in the midgut and midgut tissue, and brain of fifth instar larvae of Lymantria dispar L. and Euproctis chrysorrhoea L. following chronic exposure to dietary fluoranthene. Specific carboxylesterase activity increased significantly in the midgut tissue of E. chrysorrhoea larvae treated with a lower fluoranthene concentration. The specific patterns of isoforms expression, recorded in larvae of both species, enable efficient carboxylesterase activity as a significant part of defense mechanisms. Increased Hsp70 concentration in the brain of L. dispar larvae points to a response to the proteotoxic effects of a lower fluoranthene concentration. Decreased Hsp70 in the brain of E. chrysorrhoea larvae in both treated groups can suggest induction of other mechanisms of defense. The results indicate the importance of the examined parameters in larvae of both species exposed to the pollutant, as well as their potential as biomarkers.

Implications of long-term exposure of a Lymantria dispar L. population to pollution for the response of larval midgut proteases and acid phosphatases to chronic cadmium treatment

Cadmium (Cd) presence in terrestrial ecosystems is a serious threat that requires continuous development of biomonitoring tools. Ideally, a suitable biomarker of exposure should respond to the toxicant consistently in different populations regardless of previous exposure to pollution. Here we considered the activities and isoform patterns of certain proteases and acid phosphatases (ACP) in the midgut of Lymantria dispar larvae as well as the integrated biomarker response (IBR) for application in Cd biomonitoring. We compared the responses of caterpillars originating from unpolluted and polluted localities after they had been chronically subjected to dietary Cd (50 and 100 μg Cd/g dry food). The population inhabiting the unpolluted forest was far more sensitive to Cd exposure as the activities of total proteases, trypsin (TRY) and leucine aminopeptidase (LAP) were mostly reduced while the activities of total and non-lysosomal ACP were increased. Non-lysosomal ACP activity was elevated in larvae from the contaminated site in response to the higher Cd concentration. Exposure to the metal resulted in numerous alterations in the pattern of enzyme isoforms, but the responses of the two populations were similar except that larvae from the polluted locality were more tolerant to the lower Cd concentration. Non-lysosomal ACP activity and the appearance of ACP isoforms 4 and 5 together with the IBR index are the most promising indicators of Cd presence, potentially applicable even in populations with a history of exposure to pollution. TRY and total ACP activities could be used to monitor populations at uncontaminated localities.

Effects of fluoranthene on digestive enzymes activity and relative growth rate of larvae of lepidopteran species, Lymantria dispar L. and Euproctis chrysorrhoea L

Fluoranthene is one of the most abundant polycyclic aromatic hydrocarbon pollutants in the environment and it may accumulate in plant leaves which are the main food source for phytophagous insect species. The aim of this study was to establish the effects of dietary fluoranthene on specific activities of digestive enzymes and expression of their isoforms in the midgut, and the relative growth rates of Lymantria dispar and Euproctis chrysorrhoea larvae. Exposure to fluoranthene led to significantly decreased trypsin activity in the midgut of larvae of both species. Leucine aminopeptidase activity decreased significantly in the midgut of L. dispar larvae exposed to the lower concentration of fluoranthene, but that enzyme activity showed the opposite trend in E. chrysorrhoea larvae. There was no pollutant induced changes in lipase activity in L. dispar, while elevated enzyme activity was recorded in the midgut of E. chrysorrhoea larvae exposed to the lower concentration of fluoranthene. Different patterns of expression of enzyme isoforms were noticed. Relative growth rates of both species significantly decreased in fluoranthene treated larvae. These responses indicate to the significance of relationships between physiological changes and fitness-related traits in L. dispar and E. chrysorrhoea larvae affected by pollutant, and contribute to understanding the mechanisms of their adjustment to stressful conditions.

Sensitivity of midgut physiological parameters of Lymantria dispar L. larvae to benzo[a]pyrene in populations with different multigeneration contact to environmental pollutants

Accumulation of organic pollutants in the environment calls for sensing physiological parameters adequate to indicate the presence of contaminants and their effects on ecosystems. Evidence points to the importance of insect adaptations in their habitats for the assessment of sensitive biomarkers so we examined the influence of origin and multigenerational adaptations of the Lymantria dispar larvae to chronic benzo[a]pyrene (B[a]P) treatment under laboratory conditions. The main aim was to compare reactions of larvae from unpolluted and polluted forests using alkaline phosphatase (ALP), acid phosphatase (ACP), and carboxylesterase (CE) specific activities in the midgut, including electrophoretic isoform patterns; midgut expression levels of Hsp70, larval development time (DT), and midgut mass (MM), after chronic exposure to 5 and 50 ng of B[a]P/g dry food weight. The biomarker potential of these parameters regarding larval pre-exposure history to pollution was estimated by principal component analysis (PCA). B[a]P treatment resulted in inhibition of ALP activity, a rise of CE activity, and reduction of MM in larvae from the unpolluted forest, while the population from the polluted forest showed significant elevation of Hsp70 expression in the midgut, prolonged DT, and reduction of MM. PCA confirmed variations in responses of the selected parameters regarding population origin. The obtained results provide insight into insect population variability concerning physiological responses to pollutants. It is indicative that all investigated physiological parameters of L. dispar larvae showed origin-dependent responses to long-term presence of B[a]P, which may be of great importance in ecotoxicological research.

Biological effects of chronic exposure of Blaptica dubia (Blattodea: Blaberidae) nymphs to static and extremely low frequency magnetic fields

In this paper, we analyzed the effects of chronic exposure (5 months) to static magnetic field (110 mT; SMF) and extremely low frequency magnetic field (ELF MF; 10 mT, 50 Hz) on Blaptica dubia nymphs. We have examined acetylcholinesterase (AChE) activity and heat shock protein 70 (HSP70) level, two sensitive biomarkers of stress in terrestrial insects. Relative growth rate (RGR), as a life history trait, was estimated. AChE activity was determined spectrophotometrically and HSP70 levels were quantified using indirect non-competitive ELISA and Western blotting. Calculated RGR was significantly changed upon exposure to both types of ambiental MFs. The effects of chronic exposure of B. dubia nymphs to SMF and ELF MF (50 Hz) were observed as decreased activity of AChE. The increased level of HSP70 was present only after exposure to SMF. The strength of ELF MF was most likely below the energy level needed to induce the expression of this stress protein. Different patterns of the expression of two HSP70 isoforms, where isoform 2 was sensitive only to SMF, are most likely a possibly switch - off in the expression of constitutive and/or inducible HSP70 isoforms.

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.

The impact of chronic exposure to a magnetic field on energy metabolism and locomotion of Blaptica dubia

Purpose: This study deals with a comparative analysis of the effects of chronic exposure to a static magnetic field (SMF) and an extremely low frequency magnetic field (ELF MF) in Blaptica dubia nymphs. The outcome of such treatment on insect and fat body mass, glycogen and total lipid content in the fat body and locomotion, as an energy demanding process, were examined.Materials and methods: One-month-old nymphs of B. dubia were exposed to an SMF (110 mT) or ELF MF (50 Hz, 10 mT) for 5 months. Their locomotion was monitored in the 'open-field' test for 10 min and expressed as travel distance, time in movement and average speed while in motion. After that, fat body mass and content of its main components (glycogen and total lipids) were determined. Nymph body mass was also estimated after 1 and 5 months of MF treatment.Results: Chronic exposure to the SMF and ELF MF decreased nymph body mass and glycogen content in the fat body but increased all examined parameters of locomotion. In addition, chronic SMF treatment elevated total lipid content in the fat body, while chronic ELF MF treatment reduced fat body mass and total lipid content.Conclusions: These findings indicate that B. dubia nymphs are sensitive to the applied MFs and possess different strategies for fuel usage in response to the SMF and ELF MF in order to satisfy increased energy demands and to overcome stressful conditions.

Effect of fluoranthene on antioxidative defense in different tissues of Lymantria dispar and Euproctis chrysorrhoea larvae

This study examined the effect of long-term exposure to environmentally relevant concentrations of dietary fluoranthene (6.7 and 67 ng / g dry food weight) on defense mechanisms of the polyphagous forest insects Lymantria dispar L. and Euproctis chrysorrhoea L. The activities and expression of isoforms of superoxide dismutase (SOD) and catalase (CAT), the activities of glutathione S-transferase (GST) and glutathione reductase (GR), and total glutathione content (GSH) were determined in the whole midgut and midgut tissue, while SOD and CAT activities were assessed in hemolymph of the larvae. The results showed significant changes of enzyme activities, with more pronounced responses in larval midgut tissues, and between-species differences in patterns of response. Significantly increased activity of SOD was recorded in the whole midgut and midgut tissue of L. dispar larvae, as well as in midgut tissue of E. chrysorrhoea larvae. Fluoranthene increased CAT activity in midgut tissue of L. dispar larvae, and in the whole midgut and midgut tissue of E. chrysorrhoea larvae. Different expression patterns were detected for enzyme isoforms in tissues of larvae exposed to dietary fluoranthene. Total GSH content and GST activity increased in E. chrysorrhoea larval midgut tissue. Significantly decreased SOD activity in hemolymph of L. dispar larvae, and opposite changes in CAT activity were recorded in the hemolymph of larvae of two insect species. The tissue-specific responses of enzymes to dietary fluoranthene, recorded in each species, enabled the larvae to overcome the pollutant induced oxidative stress, and suggest further assessment of their possible use as early-warning signals of environmental pollution.

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.

Effects of dietary fluoranthene on nymphs of Blaptica dubia S. (Blattodea: Blaberidae)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants which exert detrimental effects on living beings. Considering the health risk associated with exposure to these pollutants, their presence in food increases efforts to establish early-warning indicators of pollution. We aimed to examine the effects of environmentally relevant concentrations of fluoranthene (0.2 ng and 18 ng/g dry weight of diet) on the activities of midgut antioxidant and detoxification enzymes in Blaptica dubia. Significant changes of superoxide dismutase and catalase activities, recorded at the higher fluoranthene concentration regardless of the exposure time, suggest that they may be used as biomarkers of PAH pollution. Increased GST activity and decreased total GSH content, detected upon acute exposure to the lower concentration, indicate processes of detoxification. Reorganization of B. dubia mechanisms of defense in response to oxidative stress caused by exposure to dietary PAH point to the necessity for further examination of fluoranthene actions.