Nutritive stress effects on growth and digestive physiology of Lymantria dispar larvae

The effects of parental and offspring diet on larval growth, food consumption and utilization, and activities of three digestive enzymes (a-amylase trypsin, leucine aminopeptidase) were examined in extremely polyphagous insect, the gypsy moth (Lymantria dispar). In parental generation, gypsy moth larvae were reared on oak (Quercus cerris) leaves as optimal host or beech (Fagus silvatica) leaves which contains flavonoids and alkaloids. In offspring generation, after molting into the 4th instar, they were either switched from oak to beech or remained on oak leaves. Decreased growth and food utilization efficiency, increased assimilation efficiency and activities of a-amylase and trypsin were recorded in larvae switched to beech leaves. Significant parental effects were demonstrated for fourth instar duration, weight of fifth instar larvae and specific activity of leucine aminopeptidase. Physiological, ecological and evolutionary context of the obtained results were stressed in the present paper.Kod gubara (Lymantria dispar), izrazito polifagnog insekta, ispitivan je efekat ishrane u roditeljskoj i potomačkoj generaciji na rast larvi konzumaciju i utilizaciju hrane i aktivnost tri digestivna enzima (a-amilaze, tripsina, leucin aminopeptidaze). Larve gubara su u roditeljskoj generaciji gajene na lišću hrasta (Quercus cerris) kao optimalnom domaćinu ili lišću bukve (Fagus silvatica) koje sadrži flavonoide i alkaloide. U potomačkoj generaciji, posle ulaska u IV stupanj, larve su ili prebačene sa hrastovog na bukovo lišće ili su nastavile da se hrane hrastovim lišćem. Kod larvi prebačenih na ishranu bukovim lišćem pokazan je smanjen rast i efikasnost utilizacije hrane, povećana efikasnost asimilacije i aktivnost a-amilaze i tripsina. Značajan parentalni efekat je dobijen za trajanje IV stupnja, težinu larvi u V stupnju i specifičnu aktivnost leucin aminopeptidaze. U ovom radu je istaknut fiziološki, ekološki i evolucioni kontekst dobijenih rezultata

Neurohormones in insect stress: A review

The neurohormones are the master regulators of all life processes in insects and they create a strategy of stress protecting events. Neurohormones are synthesized mainly in insect brain neurosecretory neurons. Various stressors of different intensity cause specific changes which influence on neurosecretory neurons activity and synthesis of neurohormones (biogene amines, ecdysiotropins, ecdysiostatins, allatoregulatory neurohormones, adipokinetic neurohormones, etc.). Biogene amines in insects may function as neurohormones controlling carbohydrate and lipid metabolism as the primary response of the insects to the effect of stressors. Intermediary metabolism in insects is mainly regulated by adipokinetic hormones which supply organism by energy especially in extreme conditions. Stress induces changes in release of ecdysioregulatory and allatoregulatory neurohormones and modificates ecdysones and juvenile hormones synthesis in prothoracic gland and corpora allata. The involvement of hormones of an ecdysteroid or JH type in response to stress creates the danger of an untimely induction of morphogenetic process in target cells. Limiting the quantity of secreted hormones and shortening the period when target cells are sensitive to morphogenetic stimuli removes this danger.Neurohormoni regulišu sve životne procese insekata i kreiraju strategiju odgovora organizma na delovanje stresora. Neurohormoni se u najvećoj meri sintetišu u neurosekretnim neuronima protocerebralnog regiona mozga insekata. Stresori različitih osobina i intenziteta specifično menjaju aktivnost neurosekretnih neurona i sintezu neurohormona (biogenih amina, egdizotropina, egdizostatina, alatoregulatornih neurohormona, adipokinetičkih neurohormona itd.). Biogeni amini imaju ulogu u kontroli metabolizma ugljenih hidrata i lipida u početnim fazama stresnog odgovora insekata. Intermedijerni metabolizam je regulisan dobrim delom adipokinetičkim neurohormonima koji učestvuju u obezbeđivanju dovoljne količine energije koja je potrebna za prevazilaženje ekstremnih uslova. Stres izaziva promene u lučenju egdizoregulatornih i alatoregulatornih neurohormona i modifikuje intenzitet sinteze egdizona i juvenilnih hormona u protorakalnoj žlezdi i corpora allata. Promene u količini egdizona i juvenilnog hormona u stresu povećavaju rizik početka vremenski neadekvatnih morfogenetskih promena u tkivima insekata. Stresom izazvane promene u količini morfogenetskih neurohormona su ograničene a i periodi osetljivosti ćelija na morfogenetske stimuluse se menjaju u stresu ograničavajući donekle mogućnost neadekvatnih morfogenetskih promena.nul

The effect of the allelochemical quercetin on the survival of Lymantria dispar L.

nul

Nutritive stress effects on growth and digestive physiology of Lymantria dispar larvae

The effects of parental and offspring diet on larval growth, food consumption and utilization, and activities of three digestive enzymes (a-amylase trypsin, leucine aminopeptidase) were examined in extremely polyphagous insect, the gypsy moth (Lymantria dispar). In parental generation, gypsy moth larvae were reared on oak (Quercus cerris) leaves as optimal host or beech (Fagus silvatica) leaves which contains flavonoids and alkaloids. In offspring generation, after molting into the 4th instar, they were either switched from oak to beech or remained on oak leaves. Decreased growth and food utilization efficiency, increased assimilation efficiency and activities of a-amylase and trypsin were recorded in larvae switched to beech leaves. Significant parental effects were demonstrated for fourth instar duration, weight of fifth instar larvae and specific activity of leucine aminopeptidase. Physiological, ecological and evolutionary context of the obtained results were stressed in the present paper.Kod gubara (Lymantria dispar), izrazito polifagnog insekta, ispitivan je efekat ishrane u roditeljskoj i potomačkoj generaciji na rast larvi konzumaciju i utilizaciju hrane i aktivnost tri digestivna enzima (a-amilaze, tripsina, leucin aminopeptidaze). Larve gubara su u roditeljskoj generaciji gajene na lišću hrasta (Quercus cerris) kao optimalnom domaćinu ili lišću bukve (Fagus silvatica) koje sadrži flavonoide i alkaloide. U potomačkoj generaciji, posle ulaska u IV stupanj, larve su ili prebačene sa hrastovog na bukovo lišće ili su nastavile da se hrane hrastovim lišćem. Kod larvi prebačenih na ishranu bukovim lišćem pokazan je smanjen rast i efikasnost utilizacije hrane, povećana efikasnost asimilacije i aktivnost a-amilaze i tripsina. Značajan parentalni efekat je dobijen za trajanje IV stupnja, težinu larvi u V stupnju i specifičnu aktivnost leucin aminopeptidaze. U ovom radu je istaknut fiziološki, ekološki i evolucioni kontekst dobijenih rezultata

The effect of the allelochemical quercetin on the survival of Lymantria dispar L.

nul

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).

Trypsin activity in the midgut of gypsy moth (Lymantria dispar L.)larvae during the intermolt period

nul

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

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