Vesna Perić Mataruga

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.

Effects of ghrelin on the feeding behavior of Lymantria dispar L. (Lymantriidae) caterpillars.

Ghrelin is a 28-amino acid peptide which has significant effects on animal appetite, thus influencing body mass. The aim of our study was to examine the effects of ghrelin on the feeding behavior and physiology 4th instar caterpillars of the pest insect, Lymantria dispar L. Treatment of 4th instar caterpillars with four subpicomolar amounts of ghrelin had a positive influence on daily food intake, frass elimination, body mass. Also, locomotor activity increased, while stadium duration decreased in treated caterpillars. The similarity between the effects of ghrelin on caterpillar physiology and those in mammals suggests that using this model system for further studies of neuroendocrinological processes underlying feeding could lead to essential information about more complex organisms.

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.

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.

Influence of dietary cadmium exposure on fitness traits and its accumulation (with an overview on trace elements) in Lymantria dispar larvae

Bioaccumulation and excretion of heavy metals in insects is only partially clarified. We have investigated cadmium accumulation in the feces, head and integument of Lymantria dispar (Lepidoptera: Lymantriidae) larvae exposed to chronic dietary intake of cadmium. The aim of the experiment was to establish modalities of metal accumulation, primarily cadmium, as well as changes in fitness traits in two insect populations receiving 50 or 100μgCd/g dry food. The egg-masses originated from two localities: a protected nature reserve (unpolluted population) and an area near a busy highway (polluted population) in Serbia. At both added dietary levels cadmium concentration was highest in feces. Small alterations in metal concentrations after both cadmium treatments were detected in the integument. It was established that irrespective of population origin, the modality of decline of larval mass and relative growth rate (RGR) was similar. Concentrations of Cu and Zn in the integument were approximately the same regardless of dietary cadmium intake. However, cadmium accumulation in the examined tissues, as well as variability of fitness traits depended on population origin and cadmium concentration. In larvae from both populations not given contaminated food the head was the organ with the greatest accumulation of trace elements. Our results reveal how invasive phytophagous insects cope with high metal concentrations in their food by body mass (RGR) reduction and energy allocation towards processes that enable accumulation of cadmium and other trace elements in different tissues.

Mesoporous silica nanoparticles SBA-15 loaded with emodin upregulate the antioxidative defense of Euproctis chrysorrhoea (L.) larvae

The study presented here aims to elucidate the effects of emodin (EO = 1,3,8-trihydroxy-6-methylanthraquinone) in its free form and when loaded into a mesoporous silica nanocarrier SBA-15 (→ SBA-15|EO) on the activities of the main antioxidative enzymes, superoxide dismutase, catalase, glutathione S-transferase, and glutathione reductase, in larvae of a polyphagous insect pest, the browntail moth Euproctis chrysorrhoea (L.). The results show that only SBA-15|EO upregulates the activities of the tested antioxidative enzymes. These results point to significant differences in the effectiveness of the compound in the free versus the loaded form.

Response of α-glucosidase in gypsy moth larvae to acute and chronic dietary cadmium.

We investigated the effects of acute and chronic treatments with cadmium at 10 μg Cd/g dry food and 30 μg Cd/g dry food on α-glucosidase activity of the 4th instar larvae of Lymantria dispar (Lepidoptera: Lymantriidae) as well as subsequent recovery. Enzyme inhibition was recorded during acute exposure to 30 μg Cd/g dry food and during chronic treatment at the lower metal concentration. After three days recovery from 10 μg Cd/g dry food, the α-glucosidase activity returned to the control level. One-way ANOVA showed that cadmium significantly influenced the activity of α-glucosidase during all treatments. The index of phenotypic plasticity was higher during chronic treatment at 10 μg Cd/g dry food than at 30 μg Cd/g as well as during the recovery. We detected four glucosidase isoforms by NATIVE PAGE. The activities and expressions of the isoforms depended on both larval genotype and cadmium treatment.