Anja Gavrilović

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.

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.

Tannic acid modulates the activity of bombyxin- and PTTH-producing neurons in Lymantria dispar L. (Insecta: Lepidoptera) caterpillars

Abstract Lymantria dispar caterpillars were exposed for 3 days to tannic acid, added to the artificial diet in the following concentrations: 1, 2.5 and 5%. Changes in the morphometric parameters of medial A2 bombyxin immunopositive and dorsolateral L2` prothoracicotropic (PTTH) immunopositive neurosecretory neurons (nsn; sizes of six nsn, the size of their nuclei, and quantification of cytoplasm density) were analysed upon caterpillars’ exposure to this allelochemical. Protein band density, obtained by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) electrophoresis, from regions of bombyxin and PTTH molecular mass (Mr) were estimated. A2 nsn decreased in size, while the size of their nuclei did not change significantly. Relative cytoplasm density and relative band density from the bombyxin Mr region (Mr 4–5 kD) were decreased upon exposure to 1% and 2.5% tannic acid, while the addition of 5% tannic acid to artificial diet increased all of these parameters. Results suggested that lower concentrations of tannic acid stimulate the release of neurosecretory material from A2 nsn, most probably bombyxin-like protein. High tannic acid concentration (5%) probably allocates resources towards induction of other stress protective components instead of bombyxin-mediated metabolic stress response mechanisms. In L2` nsn, the size of nsn, nuclei and the relative cytoplasm density were increased, and relative band density from the region of big PTTH form (Mr 11–15 kD) was higher in all treatments in comparison to control. Results indicate that PTTH is synthesised and stored in the cytoplasm of L2` nsn.