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Temperature and food quality are the most important environmental factors determining the performance of herbivorous insects. The objective of our study was to evaluate the responses of the spongy moth (formerly known as the gypsy moth) [Lymantria dispar L. (Lepidoptera: Erebidae)] to simultaneous variation in these two factors. From hatching to the fourth instar, larvae were exposed to three temperatures (19 °C, 23 °C, and 28 °C) and fed four artificial diets that differed in protein (P) and carbohydrate (C) content. Within each temperature regime, the effects of the nutrient content (P+C) and ratio (P:C) on development duration, larval mass, growth rate, and activities of digestive proteases, carbohydrases, and lipase were examined. It was found that temperature and food quality had a significant effect on the fitness-related traits and digestive physiology of the larvae. The greatest mass and highest growth rate were obtained at 28 °C on a high-protein low-carbohydrate diet. A homeostatic increase in activity was observed for total protease, trypsin, and amylase in response to low substrate levels in the diet. A significant modulation of overall enzyme activities in response to 28 °C was detected only with a low diet quality. A decrease in the nutrient content and P:C ratio only affected the coordination of enzyme activities at 28 °C, as indicated by the significantly altered correlation matrices. Multiple linear regression analysis showed that variation in fitness traits in response to different rearing conditions could be explained by variation in digestion. Our results contribute to the understanding of the role of digestive enzymes in post-ingestive nutrient balancing.

Deoxynivalenol (DON) is one of the most prevalent type B trichothecene mycotoxins present in cereals such as: wheat, rye, barley, oats and corn. It initiates a wide range of toxic effects on human and animal health. As an edible insect species for the growing human population, Tenebrio molitor is typically fed on cereal bran or flour. In the present study T. molitor L. larvae were grown for two weeks on wheat bran artificially contaminated with DON at four concentrations: 4.9 μg/g, 8 μg/g, 16 μg/g and 25 μg/g. The effects of DON intake on survival, growth, activity of the antioxidant enzymes - superoxide dismutase (SOD) and catalase (CAT) and the phase II biotransformation enzyme - glutathione-S-transferase (GST), protein content and locomotor activity were monitored in two-month-old T. molitor larvae. The study revealed that DON at concentrations ranging from 4.9 to 25 μg/g wheat bran reduced larval body weight and protein content. Furthermore, it increased SOD and GST activity, had no effect on CAT activity. Also, this study showed that presence of DON in these concentrations has no direct detrimental effects on larval survival, but reduced locomotor activity. The observed effects were particularly pronounced in the larvae given the highest DON concentration 25 μg/g. These finding reveals that DON in artificially contaminated wheat bran at concentrations up to 25 μg/g is able to induce dose-dependent physiological and behavioral changes in T. molitor larvae.

The traffic pressure is increasing, resulting in the emission of atmospheric pollution. Soil organisms will need to respond to pollution stressors. Among them, land snails are valuable indicators of ecosystem disturbance. In this study, land snails Helix pomatia were sampled from three city localities with different traffic intensity. Oxidative stress biomarkers catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione-S-transferase (GST) in the foot muscle (FM) and hepatopancreas (HP) tissue were determined. Also, five heavy metal (Cd, Cu, Ni, Pb, and Zn) concentrations were quantified in soil and tissue samples. According to the results, the highway induces the strongest contamination on the surrounding environment, with the highest metal concentrations measured in soil and snails. At the most polluted locality, only Cd exceeded some soil guidelines authorities that we referred to in this study. In addition, tissue Cd concentrations exceeded the United States Environmental Protection Agency (USEPA) value (1 mg kg−1) for soil invertebrate toxicity at all localities making it likely responsible for generating adverse effects in snails. Regarding HP, the CAT and GST are the most sensitive parameters that could be useful as oxidative stress biomarkers in snails exposed to the actual metals in the environment. On the other hand, in FM tissue, the most pronounced changes were recorded for GPX and GR. Based on tissue-specific enzyme responses, three urban populations were clearly separated. Therefore land snails are the promising candidates for quick field-based biomarker studies after showing a tissue-specific concentration-dependent induction of certain enzymes to heavy metals.

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.

Because food proteins are crucial for insect survival, growth, and fecundity, enzymes involved in their digestion have attracted the attention of fundamental entomologists studying the mechanisms and patterns of dietary specialization, and applied entomologists searching for more efficient modes of pest control. Most insects digest proteins using trypsin, an endopeptidase that cleaves polypeptide chains on the carboxyl side of arginine and lysine, two basic amino acids. As the most ancestral proteinase, trypsin is wide-spread in the digestive tract of insects from various orders and with various feeding habits. The present review focuses on biochemical and molecular characteristics, mechanisms of regulation, and adaptive/non-adaptive changes of trypsin activity in response to heterogeneous food environments in a phylogenetic context. Within- and among-species variations in trypsin structure and regulation that contribute to better matching with specific food types are emphasized. We also discuss the relevance of these data for choosing an appropriate strategy for control of insect pests. Pest control strategies to reduce trypsin activity by interfering with substrate binding or trypsin synthesis and secretion have been suggested. Successful application of these procedures requires a multidisciplinary approach and knowledge about digestive physiology of the pest, as well as the structural characteristics of trypsins that determine their interaction with proteinaceous inhibitors and other food compounds, about patterns of developmental changes in trypsin gene expression, adaptive responses of insects to food composition, and various environmental effects on trypsin activity.

Gypsy moths and powdery mildew play a significant role in oak decline processes. However, information is lacking on the effects on the gypsy moth of impaired tree vitality caused by defoliation or parasite infection. We assessed how pedunculate oak leaves collected from vigorous, declining, and infected trees influenced gypsy moth preference and performance (growth and nutritional indices). We found a negative effect of powdery mildew-infected leaves on gypsy moth performance, while declining trees had positive effects on gypsy moth performance and preference. All examined parameters of larvae fed declining oak leaves were higher than those of larvae fed vigorous oak leaves. Increased growth on declining oak leaves was caused by both higher consumption and more efficient food utilization. The results of this research could help us to better understand multitrophic interactions in complex communities such as oak forests. Postdocs in the field of biological sciences at Mendel University {[}CZ.1.07/2.3.00/30.0017]; European Social Fund; state budget of the Czech Republic; project ``Studying climate change and its influence on the environment: impacts, adaptation and mitigation{''} - Ministry of Education and Science of the Republic of Serbia {[}43007]

To assess the plastic and genetic components of variation in responses of gypsy moth (Lymantria dispar) 4th instar larvae to temperature and food quality, we applied a split-family four-environment experimental design where full-sibs were reared on two constant temperatures (23°C and 28°C) and two concentrations of dietary nitrogen (1.5 and 3.7% dry weight). A temperature of 28°C and low dietary nitrogen decreased larval weight and prolonged larval developmental time, while viability was not affected. Only a marginally significant interaction between the two environmental factors was found for larval weight. The broad-sense heritability for larval developmental time did not change across environments, and across-environment genetic correlations were close to one. Heritability for larval weight depended on environmental and across-environmental genetic correlations that were not significant. There was no evidence of a trade-off between developmental time and larval weight. The implications of the obtained results for the evolution of phenotypic plasticity in complex environments are discussed. [Acknowledgments. This work was supported by Ministry of Education and Science of Serbia, grant No. 173027.]

Gypsy moth (Lymantria dispar L.) females and males were chronically exposed to three sublethal cadmium concentrations (10, 30 and 50 mg/g dry food mass) in order to assess the effects of cadmium on larval and pupal duration, pupal mass and longevity. On average, the presence of cadmium in food did not affect larval duration while shortened pupal duration and reduced pupal mass and longevity were recorded. The most significant effects were obtained at the highest cadmium concentration. Females and males did not differ in sensitivity of life history traits to cadmium exposure. It is concluded that (1) cadmium exerts a strong adverse impact on the growth and development of gypsy moths, and (2) the significance of the cadmium effects depends on the dose.

Periodic fluctuations in density impose different selection pressures on populations of outbreaking Lepidoptera due to changes in their nutritional environment. The maternal effects hypothesis of insect outbreak predicts the transmission of this nutritional "information" to subsequent generations and alterations in offspring life-history traits. To test for these time-delayed effects of the parental generation, we compared life-history traits and their variation and covariation among laboratory-reared gypsy moths hatched from egg masses collected from low- and medium-density populations. Decreased individual performance was recorded in offspring from the medium-density population, indicating reduced egg provisioning under crowding conditions. Genetic variance and covariance were also shown to be sensitive to density of the parental generation. In gypsy moths from the medium-density population, quantitative genetic analysis revealed significantly higher broad-sense heritabilities for development duration traits and demonstrated a trade-off between development duration and body size.

Bean weevil, Acanthoscelides obtectus (Say) (Coleoptera: Chrysomelidae, Bruchinae) is a cosmopolitan pest of legume stored products. Storages with various legume seeds can facilitate shifts of the weevil from its primary host, common bean (Phaseolus vulgaris L.), to other legume species and enable host expansion, i.e. broadening of the range of acceptable plant-hosts. In the first generation of host shift, survival of an insect depends on ability to adjust its physiology to altered content of nutrients and secondary metabolites in novel host. On a long-term scale, physiological adaptations to a new host can comprise modifications both in level and plasticity of physiological traits. Changes in activity of phosphatases play an essential role in this process due to their involvement in diverse functions. This study investigated alterations in activity of total acid, lysosomal acid and alkaline phosphatases using laboratory populations of A. obtectus which were maintained either on the optimal host (common bean) or on the suboptimal host (chickpea, Cicer arietinum L.) for 28 years. To determine short-term (plastic) effects, subsets of individuals from each population were exposed to the alternative host for one generation. Our results revealed that one-generation shift to chickpea significantly increased phosphatases' activity reflecting immediate plastic response to nutritional/allelochemical stress where these enzymes might be involved in defense mechanisms. On the other hand, both level and plasticity of phosphatases' activities significantly declined as a long-term response to Cicer-based diet suggesting that selection on chickpea favored resistance mechanisms that were less costly than phosphatases. Considering diverse roles of phosphatases we suggest that such modifications could be crucial for expanding host range and might have implications on efficiency of chemical and botanical insecticides.

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The response of Morimus funereus larvae to total starvation and refeeding with qualitatively different nutritive substrates (artificial diets supplemented with yeast as a source of B complex vitamins or with a digestibility reducer-tannic acid) was examined in this paper. Refeeding resulted in a compensatory increase of larval growth. Feeding and refeeding with qualitatively different nutritive substrates affected both quality and quantity of midgut and brain proteins. The observed differences suggest the possible switching of enzyme isoforms in M. funereus midgut and changes in synthesis/secretion of neurohormones, depending on food presence and its nutritional value.

The 7-days shift of M. funereus larvae, from nature to a constant temperature of 23 degrees C led to changes in midgut and brain protein quality and quantity. The changes in midgut protein profiles are characterized by an intensified protein band Mr of 29 kD, the absence of protein Mr of 22 kD and less intense bands Mr of 8.5-2.5 kD. Electrophoretic patterns of brain proteins showed less intense Mr of 66-2.5 kD protein bands.

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 Robert's 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.

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