Larval Food Consumption Research Articles

Imidacloprid disrupts larval molting regulation and nutrient energy metabolism, causing developmental delay in honey bee Apis mellifera.

Imidacloprid is a global health threat that severely poisons the economically and ecologically important honeybee pollinator, Apis mellifera. However, its effects on developing bee larvae remain largely unexplored. Our pilot study showed that imidacloprid causes developmental delay in bee larvae, but the underlying toxicological mechanisms remain incompletely understood. In this study, we exposed bee larvae to imidacloprid at environmentally relevant concentrations of 0.7, 1.2, 3.1, and 377 ppb. There was a marked dose-dependent delay in larval development, characterized by reductions in body mass, width, and growth index. However, imidacloprid did not affect on larval survival and food consumption. The primary toxicological effects induced by elevated concentrations of imidacloprid (377 ppb) included inhibition of neural transmission gene expression, induction of oxidative stress, gut structural damage, and apoptosis, inhibition of developmental regulatory hormones and genes, suppression of gene expression levels involved in proteolysis, amino acid transport, protein synthesis, carbohydrate catabolism, oxidative phosphorylation, and glycolysis energy production. In addition, we found that the larvae may use antioxidant defenses and P450 detoxification mechanisms to mitigate the effects of imidacloprid. Ultimately, this study provides the first evidence that environmentally exposed imidacloprid can affect the growth and development of bee larvae by disrupting molting regulation and limiting the metabolism and utilization of dietary nutrients and energy. These findings have broader implications for studies assessing pesticide hazards in other juvenile animals.

Imidacloprid disrupts larval molting regulation and nutrient energy metabolism, causing developmental delay in honey bee Apis mellifera

Imidacloprid is a global health threat that severely poisons the economically and ecologically important honeybee pollinator, Apis mellifera. However, its effects on developing bee larvae remain largely unexplored. Our pilot study showed that imidacloprid causes developmental delay in bee larvae, but the underlying toxicological mechanisms remain incompletely understood. In this study, we exposed bee larvae to imidacloprid at environmentally relevant concentrations of 0.7, 1.2, 3.1, and 377 ppb. There was a marked dose-dependent delay in larval development, characterized by reductions in body mass, width, and growth index. However, imidacloprid did not affect on larval survival and food consumption. The primary toxicological effects induced by elevated concentrations of imidacloprid (377 ppb) included inhibition of neural transmission gene expression, induction of oxidative stress, gut structural damage, and apoptosis, inhibition of developmental regulatory hormones and genes, suppression of gene expression levels involved in proteolysis, amino acid transport, protein synthesis, carbohydrate catabolism, oxidative phosphorylation, and glycolysis energy production. In addition, we found that the larvae may use antioxidant defenses and P450 detoxification mechanisms to mitigate the effects of imidacloprid. Ultimately, this study provides the first evidence that environmentally exposed imidacloprid can affect the growth and development of bee larvae by disrupting molting regulation and limiting the metabolism and utilization of dietary nutrients and energy. These findings have broader implications for studies assessing pesticide hazards in other juvenile animals.

Gregarines modulate insect responses to sublethal insecticide residues

Throughout their lifetime, insects face multiple environmental challenges that influence their performance. Gregarines are prevalent endoparasites in most invertebrates that affect the fitness of their hosts, but are often overlooked in ecological studies. Next to such biotic factors, a current common challenge is anthropogenic pollution with pesticides, which causes a major threat to non-target organisms that are readily exposed to lethal or sublethal concentrations. In a laboratory study, we investigated whether the presence of gregarines modulates the food consumption and life history traits of a (non-target) leaf beetle species, Phaedon cochleariae, in response to sublethal insecticide exposure. We show that the larval food consumption of the herbivore was neither affected by gregarine infection nor sublethal insecticide exposure. Nevertheless, infection with gregarines led to a delayed development, while insecticide exposure resulted in a lower body mass of adult males and a reduced reproduction of females. Individuals exposed to both challenges suffered most, as they had the lowest survival probability. This indicates detrimental effects on the population dynamics of non-target insects infected with naturally occurring gregarines that face additional stress from agrochemical pollution. Moreover, we found that the infection load with gregarines was higher in individuals exposed to sublethal insecticide concentrations compared to unexposed individuals. To counteract the global decline of insects, the potential of natural parasite infections in modulating insect responses to anthropogenic and non-anthropogenic environmental factors should be considered in ecological risk assessment.

Evaluating the Effect of Pesticides on the Larvae of the Solitary Bees.

Current ecological risk assessments of pesticides on pollinators have primarily considered only laboratory conditions. For the larvae of solitary bees, ingestion of provisions contaminated with pesticides may increase the mortality rate of the larvae, decrease the collection rate and the population of adult solitary bees in the next year from a demographic perspective. But there are limited studies on the effects of pesticides on the larvae of solitary bees. Therefore, understanding how pesticides influence the larvae of solitary bees should be considered an integral part of pesticide ecological risk assessment. This study presents a method to expose the larvae of solitary bee, Osmia excavata, to lethal or sublethal doses of pesticide, tracking larval weight gain, developmental duration, eclosion ability, and food consumption efficiency conversion of ingested food. To demonstrate the effectiveness of this method, the larvae of O. excavata were fed with provisions containing acute lethal and sublethal doses of chlorpyrifos. Then, the above indexes of the treated larvae were investigated. This technique helps to predict and mitigate the risk of pesticides to pollinators.

The effects of adaptation to urea on feeding rates and growth in Drosophila larvae.

A collection of forty populations were used to study the phenotypic adaptation of Drosophila melanogaster larvae to urea‐laced food. A long‐term goal of this research is to map genes responsible for these phenotypes. This mapping requires large numbers of populations. Thus, we studied fifteen populations subjected to direct selection for urea tolerance and five controls. In addition, we studied another twenty populations which had not been exposed to urea but were subjected to stress or demographic selection. In this study, we describe the differentiation in these population for six phenotypes: (1) larval feeding rates, (2) larval viability in urea‐laced food, (3) larval development time in urea‐laced food, (4) adult starvation times, (5) adult desiccation times, and (6) larval growth rates. No significant differences were observed for desiccation resistance. The demographically/stress‐selected populations had longer times to starvation than urea‐selected populations. The urea‐adapted populations showed elevated survival and reduced development time in urea‐laced food relative to the control and nonadapted populations. The urea‐adapted populations also showed reduced larval feeding rates relative to controls. We show that there is a strong linear relationship between feeding rates and growth rates at the same larval ages feeding rates were measured. This suggests that feeding rates are correlated with food intake and growth. This relationship between larval feeding rates, food consumption, and efficiency has been postulated to involve important trade‐offs that govern larval evolution in stressful environments. Our results support the idea that energy allocation is a central organizing theme in adaptive evolution.

Study on varietal preference and nutritional indices of tea looper Hyposidra talaca (Lepidoptera: Geometridae) on ten selected tea varieties

To find out the varietal preference of H. talaca larvae, leaves of ten selected tea cultivars were provided separately to II, III, IV, and V instars. The food consumption by different larval instars was the maximum on TV20 followed by TV1 > K1/1 > TV22 > TV26 > TV16 > SNT8 > TS520 > HP12 > B157. The nutritional indices showed the highest ECD and ECI values on TV20 followed by other cultivars. However, AD values were inversely proportional to the ECI and ECD. Biochemical analysis of the host leaves indicated higher carbohydrate and lipid concentrations in TV20 which was positively correlated (r = 0.6351) with the mean food consumption, whereas, the lowest carbohydrate and lipid concentration was observed in TS520. The levels of secondary metabolites such as alkaloids (r = -0.6137) and flavonoids (r = -0.7403) showed a negative correlation with larval food consumption. Results of HPLC analysis showed the presence of different types of catechins like, EGC, Catechin, EC, EGCG, ECG, and caffeine in variable quantity in all cultivars that were positively correlated with larval feeding except the Gallic acid which showed a negative correlation (r = -0.5610). Based on the larval food consumption, the susceptible index of cultivars were categorized as ‘highly susceptible’ (TV20, TV1, K1/1, TV22, TV26, TV16, and SNT8), ‘susceptible’ (TS520 and HP12), and ‘moderately susceptible’ (B157). Based on cluster analysis A1 grouped (TS520 and HP12), A2 indicated B157 whereas sub-branches B1 grouped (TV22, TV16, TV26, and SNT8) and B2 grouped (TV1, TV20, and K1/1).

The Effects of Population Density on the Incidence of Developmental Deformities in Chemosensory Organs of Tobacco Hornworm Larvae (Lepidoptera: Sphingidae).

Cultures of Manduca sexta Johanssen in our laboratory were found to have larvae with missing or deformed mouthparts or antennae. Hypothesizing that these developmental deformities were caused by crowded rearing conditions, we reared larvae in four different population densities and recorded the incidence (% of larvae affected) and types of chemoreceptor deformities. Results showed that the incidence of these deformities was directly proportional to larval population density. Deformities of the maxilla and palp were the most frequent, followed by those of the antenna, epipharynx and maxillary styloconica. Life history traits of larval mass, food consumption, and rate of development were inversely related to larval density for both normal and deformed larvae. We discuss possible causes and mechanisms of these deformities and of changes to life history traits.

The steroid hormone 20-hydroxyecdysone binds to dopamine receptor to repress lepidopteran insect feeding and promote pupation.

Holometabolous insects stop feeding at the final larval instar stage and then undergo metamorphosis; however, the mechanism is unclear. In the present study, using the serious lepidopteran agricultural pest Helicoverpa armigera as a model, we revealed that 20-hydroxyecdysone (20E) binds to the dopamine receptor (DopEcR), a G protein-coupled receptor, to stop larval feeding and promote pupation. DopEcR was expressed in various tissues and its level increased during metamorphic molting under 20E regulation. The 20E titer was low during larval feeding stages and high during wandering stages. By contrast, the dopamine (DA) titer was high during larval feeding stages and low during the wandering stages. Injection of 20E or blocking dopamine receptors using the inhibitor flupentixol decreased larval food consumption and body weight. Knockdown of DopEcR repressed larval feeding, growth, and pupation. 20E, via DopEcR, promoted apoptosis; and DA, via DopEcR, induced cell proliferation. 20E opposed DA function by repressing DA-induced cell proliferation and AKT phosphorylation. 20E, via DopEcR, induced gene expression and a rapid increase in intracellular calcium ions and cAMP. 20E induced the interaction of DopEcR with G proteins αs and αq. 20E, via DopEcR, induced protein phosphorylation and binding of the EcRB1-USP1 transcription complex to the ecdysone response element. DopEcR could bind 20E inside the cell membrane or after being isolated from the cell membrane. Mutation of DopEcR decreased 20E binding levels and related cellular responses. 20E competed with DA to bind to DopEcR. The results of the present study suggested that 20E, via binding to DopEcR, arrests larval feeding and promotes pupation.

Effects of DEHP on post-embryonic development, nuclear receptor expression, metabolite and ecdysteroid concentrations of the moth Spodoptera littoralis

Di (2-ethylhexyl) phthalate (DEHP) is recognized in vertebrates as an Endocrine Disrupting Chemical (EDC). DEHP can alter steroid hormones production, development, reproduction and behavior in vertebrates. Only few studies investigated DEHP effects on insects. However, some recent studies on aquatic insects showed that DEHP could also act as an EDC by interfering with the signaling pathways of ecdysteroids, the main hormones involved in the control of insect post-embryonic development and physiology. The aim of the study was to investigate (1) the fate of DEHP within a terrestrial insect species by exposing larvae to food containing a wide range of DEHP concentrations and (2) the effects of this chemical on their post-embryonic development and metamorphosis, by using a multi-level approach. DEHP was shown to be present both in larvae and resulting stages, with higher concentrations in chrysalises and adults than in larvae. DEHP concentrations also decreased at the end of the last larval instar, suggesting the metabolic transformation or excretion of this chemical during this time. Only the two highest DEHP doses induced higher insect mortality, whereas low and intermediate concentrations increased larval food consumption without affecting body weight. Metabolic profiles showed that in control insects, the last three days before metamorphosis correspond to a metabolic transition, but with time-dependent changes in treated insects. Interestingly, DEHP treatments also alter both hemolymphatic ecdysteroid titers and expression levels of ecdysteroid response genes. These results confirm that DEHP can alter insect post-embryonic development and metamorphosis, by interfering with ecdysteroid pathways.

Feeding regulation by neuropeptide Y on Asian corn borer Ostrinia furnacalis.

The Asian Corn Borer Ostrinia furnacalis is a major agricultural pest. In this study, a full-length neuropeptide Y (npy) gene in O. furnacalis was sequenced and cloned from cDNA library, which contains an ORF of 273 bp by encoding 90 amino acid residues. The mature OfurNPY is composed of 29 amino acids with amidation in C-terminal. The spatiotemporal expression analysis showed that npy highest expression level was in the midgut of the fifth instar larvae (the gluttony period). When the expression of npy was knocked down by feeding or injecting dsNPY, larval food consumption, body size, and body weight were significantly inhibited compared to controls. These results indicate that NPY is an important regulator in the control of feeding of O. furnacalis.

Differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail,Papilio machaon(Lepidoptera: Papilionidae), from the Osaka population

AbstractTo clarify differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail,Papilio machaon, we reared larvae from the Osaka population under photoperiods of 16 h light : 8 h dark (LD 16:8) (long day) or LD 12:12 (short day) at 20°C. We examined the relationship between food consumption and weight during the final larval stadium and pupae, and measured the pupal supercooling point (SCP). Although the ratio of assimilation to consumption did not differ significantly between photoperiods, the ratio of assimilation to pupal weight differed significantly between individuals reared under long and short days. All diapausing pupae were brown, whereas 56% of non‐diapausing pupae were green with the remainder brown. The mean pupal body length (L), dorsal width (W1) and lateral width (W2) were larger in non‐diapausing than in diapausing pupae, and theW1/LandW1/W2ratios differed significantly between non‐diapausing and diapausing pupae. SCP was approximately –20°C and did not differ among pupae 5, 15 and 30 days after pupation under long‐day conditions. However, under short‐day conditions, mean SCP gradually decreased, stabilizing at approximately –24 to –25°C by 30 days after pupation. After freezing, some diapausing pupae emerged as adults, whereas all non‐diapausing pupae died. Both egestion and assimilation were greater under long‐day conditions. The results revealed that pupae of this papilionid exhibit seasonal polyphenism in physiological and morphological traits. Energy from food appears to be expended on increasing cold hardiness in the overwintering generation and on reproduction in the non‐overwintering generation.

The life cycle, population dynamics, and contribution to litter decomposition of Penthetria holosericea (Diptera: Bibionidae) in an alder forest

Soil sampling and pitfall traps were used to monitor Penthetria holosericea larvae and adults at approximately monthly intervals during 2001 in an alder forest near Cesky Krumlov (Czech Republic). Adult flies were detected only in late May and early June. The distribution of larval head widths indicated that there were seven larval instars and that the larvae spend most of their lives in the 6th instar. The mean (±SD) annual larval density was 140 ± 485 ind. m−2, and the mean annual larval biomass was 0.56 ± 0.37 g (dw) m−2. Larval abundance peaked in June (1078 ind. m−2), and larval biomass peaked in August (1.3 g m−2), which was before maximum litter fall in September and October. Larval food consumption relative to body mass was negatively correlated with body mass. Based on larval biomass and laboratory measurement of litter consumption, the annual consumption of litter by P. holosericea was estimated to be 137 g (dw) m−2, which represents about 40% of the annual litter fall.

Effect of Larval Density on Food Utilization Efficiency of Tenebrio molitor (Coleoptera: Tenebrionidae).

Crowding conditions of larvae may have a significant impact on commercial production efficiency of some insects, such as Tenebrio molitor L. (Coleoptera: Tenebrionidae). Although larval densities are known to affect developmental time and growth in T. molitor, no reports were found on the effects of crowding on food utilization. The effect of larval density on food utilization efficiency of T. molitor larvae was studied by measuring efficiency of ingested food conversion (ECI), efficiency of digested food conversion (EDC), and mg of larval weight gain per gram of food consumed (LWGpFC) at increasing larval densities (12, 24, 36, 48, 50, 62, 74, and 96 larvae per dm(2)) over four consecutive 3-wk periods. Individual larval weight gain and food consumption were negatively impacted by larval density. Similarly, ECI, ECD, and LWGpFC were negatively impacted by larval density. Larval ageing, measured as four consecutive 3-wk periods, significantly and independently impacted ECI, ECD, and LWGpFC in a negative way. General linear model analysis showed that age had a higher impact than density on food utilization parameters of T. molitor larvae. Larval growth was determined to be responsible for the age effects, as measurements of larval mass density (in grams of larvae per dm(2)) had a significant impact on food utilization parameters across ages and density treatments (in number of larvae per dm(2)). The importance of mass versus numbers per unit of area as measurements of larval density and the implications of negative effects of density on food utilization for insect biomass production are discussed.

Effect of Different Rearing Conditions on Larval Feeding Activity, Food Consumption, Survival and Growth of Filefish Stephanolepis cirrhifer Larvae

Effect of Different Rearing Conditions on Larval Feeding Activity, Food Consumption, Survival and Growth of Filefish Stephanolepis cirrhifer Larvae

Regulation of queen development through worker aggression in a predatory ant

Abstract Extreme developmental plasticity within the eusocial insects defines the separation between the queen and worker castes. The switch between these 2 developmental pathways is thought to be under tight social control. Although a large emphasis has been placed on the effect of larval nutrition on caste determination, workers of many species have no direct control over larval feeding. This may be particularly relevant to the early evolution of ants, when behaviors that allow fine control over larval nutrition, such as mouth-to-mouth food exchange between larvae and workers, were probably not yet present. We investigated larval-directed aggression as an alternative means to regulate queen development in the ant Harpegnathos saltator, a species that retains ancestral characteristics. We tested worker response toward natural queen-destined larvae and larvae induced to develop as queens using a juvenile hormone analog (JHA). Workers from colonies that were not rearing queens bit queen-destined larvae, whereas worker-destined larvae were not attacked. When colonies were naturally rearing queens, workers did not bite JHA-treated larvae, and a larger proportion of these larvae developed into queens compared with larvae that received biting. This supports the hypothesis that workers of H. saltator use biting to inhibit queen development during periods when the conditions for queen rearing are not met. We propose that mechanical stress, in addition to nutrition, could serve as a mechanism to regulate queen development in species that lack fine control over larval food consumption, and this may have played a role during the early evolution of eusociality in ants.

Populational divergence in the impact of three nitrogenous compounds and their combination on larvae of the frog Pelophylax perezi (Seoane, 1885)

Pollution by nitrogenous compounds is a putative stressful factor that may be causally linked to the decline of amphibians. One way to understand the potentially detrimental consequences of eutrophication on amphibian populations is to investigate variation among populations differing in exposure to nitrogen, this variation potentially indicating evolutionary potential to cope with this stressor. We have examined the effect of nitrogenous compounds ( NH 4 + ; NO 2 - ; NO 3 - , both alone and in combination) on fitness-related larval traits in four populations of Pelophylax perezi naturally exposed to different degrees of eutrophication. The results indicate that both survival and larval final size decrease at higher concentrations of these compounds, either singly or in combination. Additionally, the nitrogenous compounds were more lethal and larval food consumption and final mass were significantly reduced when they were exposed to combinations of compounds. Populations inhabiting highly polluted aquatic environments tolerated higher levels of nitrogenous compounds and showed higher survival rates and larger final size than the populations of less polluted environments, suggesting the potential to adapt to increased nitrogenous contamination in this species.

Effects of transgenic Bacillus thuringiensis-Maize on Larval Food Consumption, Utilization and Growth in the Grass-moth species Chilo partellus under Laboratory Conditions (Lepidoptera: Crambidae)

Effects of transgenic Bacillus thuringiensis-Maize on Larval Food Consumption, Utilization and Growth in the Grass-moth species Chilo partellus under Laboratory Conditions (Lepidoptera: Crambidae)

Cloning, expression and functional characterisation of chitinase from larvae of tomato moth ( Lacanobia oleracea): a demonstration of the insecticidal activity of insect chitinase

Chitinases are vital to moulting in insects, and may also affect gut physiology through their involvement in peritrophic membrane turnover. A cDNA encoding chitinase was cloned from larvae of tomato moth ( Lacanobia oleracea), a Lepidopteran pest of crops. The predicted protein contains 553 amino acid residues, with a signal peptide of 20 a.a. Sequence comparison showed 75–80% identity with other Lepidopteran chitinases. L. oleracea chitinase was produced as a functional recombinant enzyme in the yeast Pichia pastoris. A fusion protein containing chitinase joined to the N-terminus of snowdrop lectin (GNA) was also produced, to determine whether GNA could deliver chitinase to the haemolymph of Lepidopteran larvae after oral ingestion. The purified recombinant proteins exhibited similar levels of chitinase activity in vitro. Both proteins were highly toxic to L. oleracea larvae on injection, causing 100% mortality at low dose (2.5 μg/g insect). Injection of chitinase prior to the moult resulted in decreased cuticle thickness. The recombinant proteins caused chronic effects when fed, causing reductions in larval growth and food consumption by up to 60%. The oral toxicity of chitinase was not increased by attaching GNA in the fusion protein, due to degradation in the larval gut, preventing GNA acting as a “carrier”.

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.

EFFECTS OF BT RICE ON THE FOOD CONSUMPTION, GROWTH AND SURVIVAL OF CHILO SUPPRESSAUS LARVAE UNDER DIFFERENT TEMPERATURES*

Abstract The Bt transgenic rice line, i.e. KMD1 containing a synthetic cry 1 Ab gene from Bacillus thuringiensis Berliner was tested in the laboratory for evaluating its effects on larval food consumption, growth and survival of striped stem borer (SSB), Chilo suppressalis (Walker) under different temperatures. The food consumption and body weight growth as well as the survival of both 3rd and 5th instar larvae fed on Bt rice were significantly reduced, as compared with those on the control. The temperature showed no marked effect on both food consumption and body weight growth of larvae fed on Bt rice stems since the onset of 3rd instar, conversely had significant effects as since the initial stage of 5th instar. In contrast, the temperature did not distinctly influence the survival of both 3rd and 5th instar larvae. There was a linearly positive relationship between the corrected mortality of larvae and the accumulative amount of Bt rice tissues ingested by larvae.