Preadult Parental Diet Affects Offspring Development and Metabolism in Drosophila melanogaster

When Drosophila melanogaster larvae are reared on isocaloric diets differing in their amounts of protein relative to sugar, emerging adults exhibit significantly different development times and metabolic pools of protein, glycogen and trigylcerides. In the current study, we show that the influence of larval diet experienced during just one generation extends into the next generation, even when that subsequent generation had been shifted to a standard diet during development. Offspring of flies that were reared on high protein relative to sugar underwent metamorphosis significantly faster, had higher reproductive outputs, and different metabolic pool contents compared to the offspring of adults from low protein relative to sugar diets. In addition, isofemale lines differed in the degree to which parental effects were observed, suggesting a genetic component to the observed transgenerational influences.     

Role of Fat Body Lipogenesis in Protection against the Effects of Caloric Overload in Drosophila

The Drosophila fat body is a liver- and adipose-like tissue that stores fat and serves as a detoxifying and immune responsive organ. We have previously shown that a high sugar diet leads to elevated hemolymph glucose and systemic insulin resistance in developing larvae and adults. Here, we used stable isotope tracer feeding to demonstrate that rearing larvae on high sugar diets impaired the synthesis of esterified fatty acids from dietary glucose. Fat body lipid profiling revealed changes in both carbon chain length and degree of unsaturation of fatty acid substituents, particularly in stored triglycerides. We tested the role of the fat body in larval tolerance of caloric excess. Our experiments demonstrated that lipogenesis was necessary for animals to tolerate high sugar feeding as tissue-specific loss of orthologs of carbohydrate response element-binding protein or stearoyl-CoA desaturase 1 resulted in lethality on high sugar diets. By contrast, increasing the fat content of the fat body by knockdown of king-tubby was associated with reduced hyperglycemia and improved growth and tolerance of high sugar diets. Our work supports a critical role for the fat body and the Drosophila carbohydrate response element-binding protein ortholog in metabolic homeostasis in Drosophila.     

Developmental trade-offs in caddis flies: increased investment in larval defence alters adult resource allocation

Developmental trade-offs in resource allocation across life-history stages and between different body parts are predicted by life-history theories. However, there is very little empirical evidence that these occur. We investigated these trade-offs in caddis flies by experimentally manipulating larval case construction and thereby silk expenditure. Case building diverts protein resources away from larval stores, which are of major importance to adult development in species with little or no adult feeding. We induced fifth-instar Odontocerum albicorne to build new cases and examined the consequences for the morphology of the resulting adults. Rebuilding did not alter larval food consumption or the date of entering pupation, but shortened the duration of the pupal period. Adults that had been induced to expend more silk as larvae had lighter thoraces and smaller wings than the controls, but their abdomens did not differ significantly in mass or nitrogen content. These results suggest a trade-off between larval silk production and the pattern of resource allocation within the adult. The maintenance of the abdomen is likely to preserve reproductive potential, while the reduction in thoracic and wing investment will have negative consequences for flight and associated activities, and possibly for adult longevity.     

An unlikely silk: the composite material of green lacewing cocoons

Spiders routinely produce multiple types of silk; however, common wisdom has held that insect species produce one type of silk each. This work reports that the green lacewing ( Mallada signata, Neuroptera) produces two distinct classes of silk. We identified and sequenced the gene that encodes the major protein component of the larval lacewing cocoon silk and demonstrated that it is unrelated to the adult lacewing egg-stalk silk. The cocoon silk protein is 49 kDa in size and is alanine rich (>40%), and it contains an alpha-helical secondary structure. The final instar lacewing larvae spin protein fibers of approximately 2 microm diameter to construct a loosely woven cocoon. In a second stage of cocoon construction, the insects lay down an inner wall of lipids that uses the fibers as a scaffold. We propose that the silk protein fibers provide the mechanical strength of the composite lacewing cocoon whereas the lipid layer provides a barrier to water loss during pupation.     

DFMO feeding lowers polyamine levels and causes developmental defects in the silkworm Bombyx mori

The domesticated silkworm Bombyx mori is an economically important insect that produces large quantities of silk during its 5th instar larval stage. Polyamines are important regulators of growth and have been shown to affect silk production, however their role in larval development is not completely understood. L-ornithine decarboxylase (ODC), a key regulatory enzyme in the polyamine biosynthetic pathway catalyzes the conversion of ornithine to putrescine, which is further broken down to spermidine and spermine. In this study, we set out to understand the role of ODC on the growth and development of silkworm larvae. We fed 5th instar larvae with α-difluoromethylornithine (DFMO), an ODC inhibitor and studied its impact on larval silk glands. Feeding DFMO did not alter the expression of L-ODC but led to a significant reduction in putrescine and spermidine levels. Furthermore, reduced cellular levels of polyamine led to increased oxidative stress and decreased cell viability. Subsequently, this resulted in several developmental defects at the pupal and moth stages. These findings highlight the importance of ODC in the growth and development of B. mori larvae.     

The effect of nucleopolyhedrovirus infection and/or parasitism by Microplitis pallidipes on hemolymph proteins, sugars, and lipids in Spodoptera exigua larvae

We determined the physiological effects of joint and separate nucleopolyhedrovirus (NPV) infection and parasitism by the endoparasitoid Microplitis pallidipes Szepligeti on biochemical events in the noctuid Spodoptera exigua (Hübner). The results indicated that in parasitized larvae, compared to healthy larvae, total protein concentration in host hemolymph began to decline and total sugar concentration significantly increased by the first day, while lipid content in the host body significantly increased by the second day after parasitization. Meanwhile, in jointly infected and parasitized hosts, compared to parasitized larvae, total protein concentration was consistently higher, total sugar concentration was consistently lower, and lipid content became higher by the second day after treatment. In virus-infected larvae, compared to healthy larvae, total protein concentration sharply declined during the first two days but increased by the third, while total sugar concentration increased on the second and third days after virus infection but decreased at other observation times, and lipid content began to increase by the second day after virus infection. Finally, in larvae that were both parasitized and virus-infected, compared to just virus-infected larvae, total protein concentration increased during the first two days but decreased by the third, total sugar concentration increased only on the first and fourth days, and lipid content decreased significantly on the first day but began to increase by the second day after treatment. These findings led us to conclude that parasitization inhibited protein mobilization but stimulated sugar mobilization in host hemolymph, and promoted lipid mobilization in the host body, while Spodoptera exigua NPV infection stimulated protein mobilization induced by parasitization but inhibited sugar mobilization induced by parasitization.     

Effects of Low Salinity on Adult Behavior and Larval Performance in the Intertidal Gastropod Crepipatella peruviana (Calyptraeidae)

Shallow-water coastal areas suffer frequent reductions in salinity due to heavy rains, potentially stressing the organisms found there, particularly the early stages of development (including pelagic larvae). Individual adults and newly hatched larvae of the gastropod Crepipatella peruviana were exposed to different levels of salinity stress (32(control), 25, 20 or 15), to quantify the immediate effects of exposure to low salinities on adult and larval behavior and on the physiological performance of the larvae. For adults we recorded the threshold salinity that initiates brood chamber isolation. For larvae, we measured the impact of reduced salinity on velar surface area, velum activity, swimming velocity, clearance rate (CR), oxygen consumption (OCR), and mortality (LC50); we also documented the impact of salinity discontinuities on the vertical distribution of veliger larvae in the water column. The results indicate that adults will completely isolate themselves from the external environment by clamping firmly against the substrate at salinities ≤24. Moreover, the newly hatched larvae showed increased mortality at lower salinities, while survivors showed decreased velum activity, decreased exposed velum surface area, and decreased mean swimming velocity. The clearance rates and oxygen consumption rates of stressed larvae were significantly lower than those of control individuals. Finally, salinity discontinuities affected the vertical distribution of larvae in the water column. Although adults can protect their embryos from low salinity stress until hatching, salinities <24 clearly affect survival, physiology and behavior in early larval life, which will substantially affect the fitness of the species under declining ambient salinities.     

The effects of starving versus fasting on blood composition in larval house crickets

Larval crickets (Acheta domesticus) starved for 2 days during the growth phase of the instar consumed twice as much water as larvae that ceased feeding of their own accord during the last 2 days of the last instar. The behaviour of drinking more water during starvation may compensate for dry weight loss and prevent the larvae from missing the critical weight required to initiate the next moult. During starvation the plasma volume increased while the tissue volume remained constant, which produced a shift in both organic and inorganic solutes from the tissues into the plasma. During fasting there was no change in tissue or plasma volume, therefore large osmotic adjustments were unnecessary, and the only change in plasma solutes noted was a decline in plasma proteins.The titres of proteins, lipids and amino acids remained constant during 2 days of starvation, though the amount of each increased because of the increased plasma volume. Although both the titre and the amount of plasma sugar sharply declined during starvation, there was no change in the sugar titre when the insects fasted. There was some evidence that prior to fasting the programmed gradual decline in food intake matched the decline in metabolic rate, which permitted a plasma sugar stability not evident in starved larvae. The decline in plasma proteins during the fasting phase appeared due to the removal of a larval specific protein and not a direct result of fasting.     

Hypertrehalosaemic and hyperlipaemic responses to adipokinetic hormone in fifth larval instar locusts,Locusta migratoria

In fifth instar larvae of Locusta migratoria the haemolymph lipid concentration is elevated after injection of adipokinetic hormone (AKH). This hyperlipaemic response in larvae remains substantially lower than in adults; over 75% of the mobilized lipid consists of diacylglycerol. In addition, unlike adult locusts, fifth instar larvae also exhibit a consistent, though moderate, hypertrehalosaemic response to AKH. The increases of both lipid and carbohydrate concentrations in larvae are dose-dependent, showing a significant linear regression on log dose in the range 0.2–20 pmol AKH.Glycogen phosphorylase in the fat body of fifth instar larvae as well as young adults is activated on injection of AKH, the percentage active phosphorylase increasing linearly with log dose in the range 0.04–20 pmol AKH. For a given response, a somewhat higher dose of AKH is needed in larvae than in young adults.Fat body glycogen phosphorylase is strongly activated during the period of the larval-adult ecdysis, when active phosphorylase accounts for almost half of the total enzyme, which is approximately ten times more than it is two days before, and two days after the ecdysis.The corpora cardiaca of fifth larval instar locusts already possess the potencies to elevate carbohydrate and lipid concentrations in larval haemolymph, and to activate fat body glycogen phosphorylase.     

Lipid and protein loads in pupating larvae and emerging adults as affected by the composition of Mediterranean fruit fly (Ceratitis capitata) meridic larval diets

The effects of sucrose and amino acid (aa) composition and concentration in meridic larval diets (e.g., partially defined at the chemical level) was examined on several parameters of Mediterranean fruit fly (Medfly) development. Lipid and protein levels of pupating larvae and emerging adults were examined. Different sucrose concentrations in the diet had small effects upon most of the development parameters. However, sucrose concentration significantly affected the ability of larvae to accumulate lipid reserves and proteins. Adults emerging from the different sucrose diets did not significantly differ in their lipid contents and protein loads. Specific deletions of aa from the diet, and general aa concentration, had a strong effect upon the parameters of development and pupating larvae lipids and proteins. Glycine-deletion was the most deleterious, followed by the deletion of all non-essential aa, and serine. High aa concentration in the diet has a detrimental effect upon development. Lipid contents in pupating larvae, and to some extent protein levels, were affected by aa manipulations in the diet. Lipid and protein loads in emerging adults were not significantly affected by aa manipulations. Based on the analysis of lipid frequency distribution it is suggested that the Medfly seems to regulate the level of lipid content in emerging adults within a certain range, regardless of the larval diet history or lipid contents. Proteins do not seem to be regulated as are lipids. These results point to an interesting and unexpected metabolic regulation of energetic resources during metamorphosis of the Medfly.     

Dytiscus latissimus and D. circumcinctus (Coleoptera,Dytiscidae) larvae as predators on three case-making caddis larvae

The predacious behaviour of Dytiscus circumcinctus and D. latissimus larvae was studied experimentally. When offered different prey simultaneously, D. latissimus larvae preferred cased caddis larvae relative to mayfly nymphs and isopods, whereas in D. circumcinctus the preference order was reversed. Notonectid nymphs and tadpoles were consumed in higher numbers by D. circumcinctus than by D. latissimus larvae. D. circumcinctus larvae and instar III larvae of D. latissimus most frequently captured caddis larvae through the case wall, whereas the instar I and II larvae of D. latissimus normally attacked the thorax of the exposed larva from above the front opening of the case. Limnephilus borealis, L. nigriceps and L. rhombicus caddis larvae differed in case structure, and they were all successfully captured by D. latissimus and D. circumcinctus instar II and III larvae. Neither capture success nor ingestion efficiency varied significantly between the two Dytiscus species or between different prey species. Instar II and III D. circumcinctus larvae had shorter reaction times than those of D. latissimus. The larger L. borealis and L. rhombicus larvae were preferred by the two last Dytiscus larval instars, and the handling time of these two prey was longer than that of L. nigriceps larvae.     

The effect of larval and adult nutrition on successful autogenous egg production by a mosquito

Females of most mosquito species require a blood meal to provision eggs and can be medical problems because of this dependency. Autogenous mosquitoes do not require blood to mature an initial egg batch and, instead, acquire nutrients for egg provisioning as larvae. We studied the importance of larval and adult nourishment for Ochlerotatus atropalpus which is obligatory autogenous for its first egg cycle but may ingest blood for subsequent cycles. Larval nourishment strongly influenced autogenous egg production: female larvae that were nutritionally stressed emerged as smaller adults, produced fewer eggs and emerged with less protein, lipid and glycogen stores. Female Oc. atropalpus are 100% autogenous, regardless of larval diet quality or whether females are fed sugar or water at emergence. Upon completion of the first egg batch, only females emerging from a poor larval diet ingested blood and produced a second egg batch.     

Lipid content and fatty acid composition of larvae and adults of the velvetbean caterpillar, Anticarsia gemmatalis, as affected by larval diet

Eight fatty acids were found in the food, larvae and adults of the velvetbean caterpillar, Anticarsia gemmatalis, with C16:0, C18:0, C18:1, C18:2 and C18:3 accounting for over 90% of the total. Fatty acid composition of the larvae tended to reflect that of their food. The most striking differences were the high percentages of C18:1 and C18:2 and the low percentage of C18:3 in the artificial diet and artificial diet-reared larvae compared to the foliage of three species of legume food plants (soybean, Glycine max; pigeon pea, Cajanus cajan; and hairy indigo, Indigofera hirsuta) and foliage-reared larvae. Lipid content (%dw) declined during metamorphosis from mature larva to adult with diet-reared larvae and adults exhibiting significantly higher lipid contents than foliage-reared insects. Regardless of larval food, newly eclosed adults tended to exhibit a decrease in the % of C18:3, and increases in C16:0 and C18:1 compared to larvae. Larval diet clearly influenced the fatty acid composition of larvae and adults, but only the % of C18:2 did not change between food, larvae and adults.     

Control of activity and regression of the silk glands in the last-larval instar of Galleria mellonella

The weight increase of silk glands in isolated larval abdomens is enhanced by brain implants which stimulate RNA and protein synthesis. It is proposed that, in intact last-instar larvae, a blood-borne factor from the brain promotes silk gland activity during the facultative feeding period. In the post-feeding larvae, some starving larvae and in isolated larval abdomens the silk glands regress. The regression is accelerated and the glands degenerate under the action of 20-hydroxyecdysone. This effect is not associated with an increase in protease and RN-ase activities. In the normal larvae, the protease activity increases gradually during the last instar to a maximum at the time of regression and drops in the degenerating glands. RN-ase activity is maintained at a high level in the fully active, regressing and degenerating glands The results indicate that regression and degeneration of the silk glands are caused by structural cell reorganization rather than by an appearance of cytolytic enzymes.     

Using field-evolved resistance to Cry1F maize in a lepidopteran pest to demonstrate no adverse effects of Cry1F on one of its major predators

Spodoptera frugiperda (JE Smith) represents the first documented case of field-evolved resistance to a genetically engineered crop expressing an insecticidal protein from Bacillus thuringiensis (Bt). In this case it was Cry1F-expressing maize (Mycogen 2A517). The ladybird beetle, Coleomegilla maculata, is a common and abundant predator that suppresses pest populations in maize and many other cropping systems. Its larvae and adults are polyphagous, feeding on aphids, thrips, lepidopteran eggs and larvae, as well as plant tissues. Thus, C. maculata may be exposed to Bt proteins expressed in genetically engineered crops by several pathways. Using Cry1F-resistant S. frugiperda larvae as prey, we evaluated the potential impact of Cry1F-expressing maize on several fitness parameters of C. maculata over two generations. Using Cry1F resistant prey removed any potential prey-mediated effects. Duration of larval and pupal stages, adult weight and female fecundity of C. maculata were not different when they were fed resistant S. frugiperda larvae reared on either Bt or control maize leaves during both generations. ELISA and insect-sensitive bioassays showed C. maculata were exposed to bioactive Cry1F protein. The insecticidal protein had no effect on C. maculata larvae, even though larvae contained 20?C32?ng of Cry1F/g by fresh weight. Over all, our results demonstrated that the Cry1F protein did not affect important fitness parameters of one of S. frugiperda??s major predators and that Cry1F protein did not accumulate but was strongly diluted when transferred during trophic interactions.     

Lipid peroxidation and antioxidant defence status during larval development and metamorphosis of giant prawn,Macrobrachium rosenbergii

In the present communication we studied the involvement of reactive oxygen species and alteration in antioxidant defence status during larval development and metamorphosis of giant prawn, Macrobrachium rosenbergii. Overall results indicate that there was a decline in endogenous lipid peroxidation level during larval development. Activity of superoxide dismutase was the lowest in early larval stages (Zoea-I and II) and thereafter increased in V and VI stages, followed by a decrease in the subsequent larval stages. Catalase and glutathione peroxidase did not exhibit specific pattern of changes during development. Reduced glutathione content exhibited an incremental increase during larval progression until metamorphosis. Ascorbic acid content of the larval tissue remained unaltered during development but a sharp fall was marked in its content in the post-larvae. Hence it is concluded that early larvae face high oxidative stress as evident from the high content of thiobarbituric acid reactive substances. This may be due to direct exposure of larvae to ambient oxygen of the water as well as their low antioxidant potential. However, during development with the augmentation in antioxidant reserve of the larval tissues a diminution in the oxidative stress was recorded. Thus it is presumed that antioxidant defences play an important role in providing protection to the developing larvae from oxidative assault during larval progression and metamorphosis.     

A larval serum protein of the silkworm,Bombyx mori: cDNA sequence and developmental specificity of the transcript

The Bombyx mori larval serum protein (BmLSP) is a major component of larval hemolymph proteins until early in the last instar. The cDNA for BmLSP was cloned from a library constructed from fat body RNA of penultimate instar larvae, and the complete nucleotide sequence of the 909 base pair cDNA insert was determined. The deduced 262 amino acid polypeptide included a 16 amino acid residue signal peptide and a 15 amino acid sequence prosegment. A homology search showed that BmLSP has significant similarity with microvitellogenin of Manduca sexta and the 30K proteins of B. mori. Tissue distribution and developmental profile of BmLSP mRNA were analyzed by northern hybridization. BmLSP mRNA was abundant in fat body but not detected in midgut and silk gland. BmLSP mRNA was present during the feeding periods of the fourth and fifth instar larvae, but absent during the larval molt and after the onset of cocoon spinning.     

Assessment of biochemical composition and energy reserves in larvae of the scallop Patinopecten yessoensis

Larvae of Patinopecten yessoensis increased in dry weight from ≈ 150 to 1000 ng per larva during the larval development period of 28 days. Microanalytical procedures were developed to determine the lipid, protein, carbohydrate, and ash contents from which energy levels and condition indices were derived. Replicate analyses of two sizes of P. yessoensis larvae gave coefficients of variation at or <5% for the biochemical analyses. Lipid and protein were identified as major components, and carbohydrate as a minor component providing 56.6,37.6, and 5.8 %, respectively, of the calculated energy content. The energy content of the eggs of P. yessoensis was 2.4 and 3.1 times higher than the larvae of P. yessoensis and Crassostrea gigas, respectively, derived from 20.6% lipid, 54.6% protein, and 7.2% carbohydrate. The carbohydrate in the eggs was stored principally as a glucan, considered to be glycogen, which was absent in the developing larvae. Changes in biochemical composition of P. yessoensis larvae during development showed that lipid and protein reserves were lost for ≈ 20 days and then lipid accumulated as the larvae reached premetamorphic condition.     

The chemistry of insect hemolymph. II. Trehalose and other carbohydrates

α,α-Trehalose, a sugar previously regarded as a product characteristic of certain lower plants, has been identified as a major blood sugar of insects. Trehalose has been isolated in pure form from the blood of pupae of the silk moth, Telea polyphemus, and has been recognized chromatographically in all the insects examined, which comprise 10 species belonging to 5 different orders. Trehalose has been determined quantitatively with anthrone after either chromatographic separation or chemical degradation of other sugars. In larvae and pupae of 4 species of Lepidoptera it ranges from 0.2 to 1.5 gm. per 100 ml. of blood and makes up over 90 per cent of the blood sugar; in larvae of a sawfly, about 80 per cent of the blood sugar is trehalose. In Bombyx mori and Platysamia cecropia, the pupal blood trehalose level is about half that in the mature larva, suggesting utilization of trehalose for glycogen synthesis during pupation. Small amounts of glucose and apparent glycogen are also present in the plasma of these insects. In Bombyx larval plasma there is also 0.04 to 0.12 gm. per 100 ml. of glucose-6-phosphate and smaller amounts of an apparent ketose phosphate.