Larisa Ilijin

Plastic responses of larval mass and alkaline phosphatase to cadmium in the gypsy moth larvae.

Biochemical analyses can point to toxicant presence before its effects can be detected at higher organizational levels. We investigated responses of larval mass and alkaline phosphatase (ALP) to different cadmium treatments in 4th instar gypsy moth larvae from 20 full-sib families. Changes in trait values and trait plasticities as well as their variation were monitored after acute and chronic exposure or recovery from two cadmium concentrations (Cd(1)=10microg and Cd(2)=30microg Cd/g dry food). Larval mass only decreased, without returning to the control level at recovery stage following chronic cadmium challenge. Acute stress did not change trait value but increased genetic variance of larval mass. Significant ALP activity changes, sensitivity of isozyme patterns (Mr of 60, 64, and 85kDa) and increased variation in ALP plasticity during acute exposure to cadmium point to its possible aplication as an exposure biomarker.

Metabolic response of cerambycid beetle (Morimus funereus) larvae to starvation and food quality

The response of xylophagous Morimus funereus larvae to a direct change of diet demonstrated that the larvae from nutrient-poor substrates, e.g. oak, are very sensitive to such a change. Depending on dietary protein quality and quantity, an increase of proteolytic activity, i.e. an intensified protein metabolism accompanied by changes in body mass gain, was observed. At the same time, amylolytic activity was usually decreased. In the larvae reared on Roberts diet, sensitivity to the switch in diet was lower at the level of proteolytic enzymes that remained at the control level, while amylolytic activity was elevated. If the switch to a new diet was preceded by 7-day-starvation that disturbed nutritional homeostasis, the response of the larvae was similar to that recorded upon a direct switch only after short-term feeding (24 h) upon starvation. Differences in the response to changes in the diet of the larvae from nature, those reared under laboratory conditions and those of different physiological status could be ascribed to plasticity in the expression of the genes coding for proteases and their isoenzymes, as well as to the multi-functionality of some neurosecretory neurons, synthetic products that participate in the regulation of digestive enzyme activities.

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.

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.

Acetylcholinesterase (AChE) and heat shock proteins (Hsp70) of gypsy moth (Lymantria dispar L.) larvae in response to long-term fluoranthene exposure.

Polycyclic aromatic hydrocarbons (PAHs) may affect biochemical and physiological processes in living organisms, thus impairing fitness related traits and influencing their populations. This imposes the need for providing early-warning signals of pollution. Our study aimed to examine changes in the activity of acetylcholinesterase (AChE) and the concentration of heat shock proteins (Hsp70) in homogenates of brain tissues of fifth instar gypsy moth (Lymantria dispar L.) larvae, exposed to the ubiquitous PAH, fluoranthene, supplemented to the rearing diet. Significantly increased activity of AChE in larvae fed on the diets with high fluoranthene concentrations suggests the necessity for elucidation of the role of AChE in these insects when exposed to PAH pollution. Significant induction of Hsp70 in gypsy moth larvae reared on the diets containing low fluoranthene concentrations, indicate that changes in the level of Hsp70 might be useful as an indicator of pollution in this widespread forest species.

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.

Ghrelin effect on nutritional indices, midgut and fat body of Lymantria dispar L. (Lymantriidae)

Ghrelin is a 28-amino acid peptide that has significant effects on appetite and growth in humans and animals. The aim of this study was to examine 4th instar larvae of the pest insect Lymantria dispar L. after ghrelin treatment. Parameters included changes in nutritional indices (efficiency of conversion of ingested food, efficiency of conversion of digested food, approximate digestibility); midgut and fat body mass; total proteases, trypsin and leucine aminopeptidase activities in the midgut; number, height and width of columnar and goblet cells and their nuclei in the midgut epithelium and detection of ghrelin-like immunoreactivity in the midgut tissue. Four subpicomolar injections of ghrelin (0.3pmol) or physiological saline (control) were applied every 24h. The nutritional indices were higher in the ghrelin treated than in the control group. Ghrelin treatment was also associated with elevation of midgut mass, induced digestive enzyme activities, increased fat body mass and morphometric changes in columnar and goblet cells. This is the first report of the presence of ghrelin-like hormone in endocrine cells of an insect midgut. Such information provides additional evidence for application of this relatively simple model system in the future studies of the mechanisms underlying of digestion and energy balance in more complex organisms.

Adaptive phenotypic plasticity of gypsy moth digestive enzymes

The adaptiveness of plasticity of digestive enzyme responses to allelochemical stress was tested on 32 full-sib families of gypsy moth larvae from an oak forest population (the Quercus population) and 26 families from a locust-tree forest (the Robinia population), reared either on control diet, or on tannin-supplemented diet. Using the duration of larval development as an indirect measure of fitness, phenotypic selection analyses revealed that lower specific activities of total proteases and trypsin, and higher specific activity of leucine aminopeptidase were adaptive for both populations in the control environment. Plasticity was only shown to be costly for total proteases and trypsin activity in Quercus larvae. In a stressful environment, the most apparent adaptive response was a significant increase in lipase activity. There was no plasticity cost for lipase activity. The two populations differed in the direction of selection acting on α-glucosidase activity, which favoured decreased activity in Quercus larvae and increased activity in Robinia larvae in the control environment. α-glucosidase activity in Quercus larvae is characterized by cost of homeostasis, while cost of plasticity was shown for Robinia larvae. The results obtained on the plasticity of digestive enzyme activity indicate how this generalist species copes with variation in plant allelochemicals.

Life history traits and the activity of antioxidative enzymes in Lymantria dispar L. (lepidoptera, lymantriidae) larvae exposed to benzo[a]pyrene

Increased presence of benzo[a]pyrene in the environment underlines the need for development of sensitive biomarkers for monitoring. Antioxidative enzymes could be used as early-warning signals because of their sensitivity and applicability. The activity of 2 antioxidative enzymes, superoxide dismutase (SOD) and catalase (CAT), were measured in midgut tissues of fifth instar Lymantria dispar larvae exposed to different concentrations of benzo[a]pyrene: 2 ng, 10 ng, 20 ng, 100 ng, 200 ng, and 2000 ng benzo[a]pyrene/g dry food weight. Larval development, larval mass, and relative growth rate were also monitored. The authors detected prolonged larval development, as well as reduced larval mass and relative growth rate in larvae exposed to all benzo[a]pyrene concentrations. The L. dispar midgut SOD activity was significantly increased, and 2 SOD isoforms were detected on native polyacrylamide gel electrophoresis in larvae fed on artificial diet supplemented with benzo[a]pyrene. In contrast, the control group had only 1 isoform. Catalase activity was significantly increased in all benzo[a]pyrene-treated larvae. Native gel electrophoresis showed that a switch in active CAT isoforms occurred after benzo[a]pyrene treatment. Thus, SOD and CAT in polyphagous herbivorous L. dispar larvae are very sensitive to low concentrations of benzo[a]pyrene. Therefore, they could be used as biomarkers for exposure and effects of this toxic polycyclic aromatic hydrocarbon.

Effects of fluoranthene on the fitness-related traits and antioxidative defense in Lymantria dispar L.

This study aimed to examine the effects of ubiquitous polycyclic aromatic hydrocarbon fluoranthene, supplemented to an artificial diet, on the fitness-related traits and activity of midgut antioxidative enzymes—superoxide dismutase (SOD) and catalase (CAT), and expression of their isoforms in the fifth-instar gypsy moth Lymantria dispar L. Prolonged duration of development and reduced weight and relative growth rate were recorded in larvae reared on the diets supplemented with different concentrations of fluoranthene. SOD and CAT activities were significantly higher in the midguts of fluoranthene-treated larvae, compared to that of the control group. Different expression patterns were detected for SOD as well as for CAT isoforms, depending on the supplemented concentration of fluoranthene. Obtained results suggest that the activity of these enzymes in gypsy moth larvae may be used as biomarkers for assessing pollution, even at low concentrations of the pollutant.