Activity of gypsy moth dorsolateral neurosecretory neurons under increased rearing density

Lymantria dispar caterpillars were reared under two different rearing densities for the first three days of the 4th larval instar: 5 larvae that were kept in a Petri dish (V = 80 ml) belonged to the intense stress (D1 group); 5 larvae that were kept in a plastic cup (V = 300ml) belonged to the group exposed to less intense stress (D2 group). In the control group, single larvae were reared in a Petri dish. Morphometric changes in L1, L2 and L2’ dorsolateral neurosecretory neurons (nsn) were analyzed. After keeping 5 larvae in a Petri dish, the size of L2 neurosecretory neurons (nsn) significantly increased. Rearing 5 larvae in a plastic cup significantly increased the size of L1 nsn nuclei and the number of L2’nsn. A decrease in relative band densities in the region of molecular masses (11-15 kD) that correspond to prothoracicotropic hormones in the gypsy moth was observed in the electrophoretic profiles that were obtained after both treatments in comparison to the control group. [Acknowledgments. This study was supported by the Serbian Ministry of Education and Science (Grant No. 173027).

Sensitivity of gypsy moth neurosecretory neurons to acute thermal stress

In gypsy moth caterpillars exposed to a temperature of 35°C (for 1, 12 and 24 h and caterpillars that were exposed to elevated temperature for 12 h and were allowed to recover for 12 h at 23°C), changes in the brain protein profiles and morphometric characteristics of A1’ medial and L2 lateral protocerebral neurosecretory neurons were analyzed. In all groups, protein bands with a molecular mass corresponding to that of members of heat-shock protein families were detected, indicating that acute exposure to this temperature likely induced the synthesis of HSP. Increased morphometric parameters of A1’ neurons and the large amount of neurosecretory material in the neuron body implicate that the temperature of 35°C is not in the temperature range that exerts stimulatory effects on growth and survival. Changes in the morphometric characteristics of L2 neurosecretory neurons from the lateral part of the protocerebrum, and retention of neurosecretory material in their cytoplasm indicate a low level of secretion

Effects of tannic acid on trypsin and leucine aminopeptidase activities in gypsy moth larval midgut

The effects of allelochemical stress on genetic variations in the specific activities of gypsy moth digestive enzymes (trypsin and leucine aminopeptidase) and relative midgut mass (indirect measure of food consumption), as well as variability in their plasticity, were investigated in fifth instar gypsy moths originating from two populations with different trophic adaptations (oak and locust-tree forests). Thirty-two full-sib families from the Quercus population and twenty-six full-sib families from the Robinia population were reared on an artificial diet with or without supplementation with tannic acid. Between population differences were observed as higher average specific activity of trypsin and relative midgut mass in larvae from the Robinia population. Significant broad-sense heritabilities were observed for the specific activity of trypsin in the control state, and for specific activity of leucine aminopeptidase in a stressful environment. Significantly lower heritability for relative midgut mass was recorded in larvae from the Robinia population reared under stressful conditions. Significant variability of trypsin plasticity in larvae from both populations and significant variability of leucine aminopeptidase plasticity in larvae from the Robinia population point to the potential for the evolution of enzyme adaptive plastic responses to the presence of stressor. Non-significant across-environment genetic correlations do not represent a constraint for the evolution of enzyme plasticity. [Projekat Ministarstva nauke Republike Srbije, br. 173027

Changes in Lymantria dispar protocerebral neurosecretory neurons after exposure to cadmium

Gypsy moth 4th instar caterpillars were fed for 3 days with an artificial diet supplemented with increasing cadmium (Cd) concentrations (0, 10, 30, 100 and 250 μg⁄g of dry food weight). Changes in the morphometric characteristics of A1' dorso-medial and L2 dorso-lateral neurosecretory neurons (nsn) were analyzed. In the A1' nsn, Cd supplements led to an enhanced nuclear size, except in the group treated with 250 μg Cd⁄g in the form of dry food. The size of L2 type nsn was increased in the groups provided with 30 and 100 μg Cd⁄g, while no differences in the size of nuclei was detected in L2 neurons among the experimental groups.Projekat ministarstva br. 7302

The effects of tannic acid on the fitness-related traits of Lymantria dispar L. larvae

In this study we investigated the effects of tannic acid on fitness-related traits in gypsy moth larvae from two differently adapted populations. Thirty two full-sib families from oak (suitable host plant, Quercus population), and twenty six full-sib families from locust-tree (unsuitable host plant, Robinia population) forests were reared on artificial diets with or without a 5% tannic acid supplement. Tannic acid shortened the duration of larval development till the 4th instar in the Robinia population, and decreased the mass of larvae from both Quercus and Robinia populations. Local adaptation was not recorded for any of the examined traits. In general, regardless of population origin, genetic variation (broad-sense heritability) was higher in larvae fed on the diet containing tannic acid than in larvae fed on the control diet. Variability of phenotypic plasticity was significant for the examined traits, except for larval duration traits in Quercus larvae, pointing to the potential of gypsy moth larvae from both populations for the evolution of adaptive plastic responses to new environmental conditions and the presence of stressors. Genetic correlations between the environments were positive and significantly different from 'one' and accordingly, do not represent constraint for the evolution of plasticity.Projekat ministarstva br. 17302

Sensitivity of gypsy moth neurosecretory neurons to acute thermal stress

In gypsy moth caterpillars exposed to a temperature of 35°C (for 1, 12 and 24 h and caterpillars that were exposed to elevated temperature for 12 h and were allowed to recover for 12 h at 23°C), changes in the brain protein profiles and morphometric characteristics of A1' medial and L2 lateral protocerebral neurosecretory neurons were analyzed. In all groups, protein bands with a molecular mass corresponding to that of members of heat-shock protein families were detected, indicating that acute exposure to this temperature likely induced the synthesis of HSP. Increased morphometric parameters of A1' neurons and the large amount of neurosecretory material in the neuron body implicate that the temperature of 35°C is not in the temperature range that exerts stimulatory effects on growth and survival. Changes in the morphometric characteristics of L2 neurosecretory neurons from the lateral part of the protocerebrum, and retention of neurosecretory material in their cytoplasm indicate a low level of secretion.Projekat ministarstva br. 17302

Biogenic amines in protocerebral A2 neurosecretory neurons of Lymantria dispar L. (Lepidoptera:Lymantriidae): Response to trophic stress

The number, morphometric parameters and amount of aminergic neurosecretory product of protocerebral A2 neurosecretory neurons were investigated in the fifth instar of Lymantria dispar caterpillars, following a suitable or unsuitable trophic regime. Caterpillars originated from two populations (Quercus rubra or Robinia pseudoacacia forest) and were differently adapted to trophic stress, i.e. feeding on locust tree leaves - unsuitable host plant. The number of neurosecretory neurons was higher in the caterpillars originated from Robinia population than in Quercus population, regardless of feeding. A2 neurosecretory neurons, nuclei and their nucleoli were larger in caterpillars fed with unsuitable leaves in both populations. There was more aminergic product in the A2 neurosecretory neurons of the caterpillars fed with unsuitable leaves independently of population origin

Activity of gypsy moth dorsolateral neurosecretory neurons under increased rearing density

Lymantria dispar caterpillars were reared under two different rearing densities for the first three days of the 4th larval instar: 5 larvae that were kept in a Petri dish (V = 80 ml) belonged to the intense stress (D1 group); 5 larvae that were kept in a plastic cup (V = 300ml) belonged to the group exposed to less intense stress (D2 group). In the control group, single larvae were reared in a Petri dish. Morphometric changes in L1, L2 and L2’ dorsolateral neurosecretory neurons (nsn) were analyzed. After keeping 5 larvae in a Petri dish, the size of L2 neurosecretory neurons (nsn) significantly increased. Rearing 5 larvae in a plastic cup significantly increased the size of L1 nsn nuclei and the number of L2’nsn. A decrease in relative band densities in the region of molecular masses (11-15 kD) that correspond to prothoracicotropic hormones in the gypsy moth was observed in the electrophoretic profiles that were obtained after both treatments in comparison to the control group.Projekat ministarstva br. 17302

Benzo[a]pyrene-induced changes in carboxylesterase, acetylcholinesterase and heat shock protein 70 of Lymantria dispar (Lepidoptera: Lymantriidae) from unpolluted and polluted forests

Plant vegetation accumulates polycyclic aromatic hydrocarbons (PAHs) among which benzo[a]pyrene (B[a]P) is recognized as being very toxic, including cancerogenic. Lymantria dispar L. larvae are sensitive to changes in the environment, providing potential signs of pollutant presence. We examined the chronic effects of two concentrations of B[a] P on the activity of carboxylesterase (CaE), acetylcholinesterase (AChE) and heat shock protein 70 (Hsp70) levels in the brain tissue of two populations of L. dispar larvae, originating from unpolluted and polluted habitats. We found that the relative growth rate was significantly lower in both populations and that only larvae from polluted forests were sensitive to low B[a]P concentrations, exhibiting a significant increase in brain tissue CaE activity and Hsp70 concentration. AChE activity showed no changes in response to B[a]P exposure in either population. Examined biochemical parameters indicate that their sensitivity to chronic treatment with B[a]P was highly dependent on the pre-exposure history of L. dispar larvae, suggesting that they could be promising biomarkers of B[a]P and PAH pollution in forest ecosystem

Ghrelin effects on the activities of digestive enzymes and growth of Lymantria dispar L.

Ghrelin, along with several other hormones, has significant effects on appetite and growth in humans and animals. The aim of our study was to examine changes in relative growth rates, α- and β-glucosidase activities and endocrine cell size in the midgut of 4th instar caterpillars of the pest insect Lymantria dispar L. after ghrelin treatment. Four subpicomolar injections of ghrelin (0.3 pmol) or physiological saline were applied every 24 h to two separate groups of fifteen caterpillars. Repeated administration of ghrelin in subpicomolar doses elevated the relative growth rate, induced α- and β-glucosidase activities and increased the size of endocrine cells. The results are the first data about ghrelin effects on relative growth rate, digestive enzyme activities and midgut endocrine cells in insects. This information supports the use of this relatively simple model system in future studies of mechanisms underlying digestion in complex organisms.Projekat ministarstva br. 17302