Worker honey bee ovary development: seasonal variation and the influence of larval and adult nutrition

We examined the effect of larval and adult nutrition on worker honey bee (Apis mellifera L.) ovary development. Workers were fed high or low-pollen diets as larvae, and high or low-protein diets as adults. Workers fed low-protein diets at both life stages had the lowest levels of ovary development, followed by those fed high-protein diets as larvae and low- quality diets as adults, and then those fed diets poor in protein as larvae but high as adults. Workers fed high-protein diets at both life stages had the highest levels of ovary development. The increases in ovary development due to improved dietary protein in the larval and adult life stages were additive. Adult diet also had an effect on body mass. The results demonstrate that both carry-over of larval reserves and nutrients acquired in the adult life stage are important to ovary development in worker honey bees. Carry-over from larval development, however, appears to be less important to adult fecundity than is adult nutrition. Seasonal trends in worker ovary development and mass were examined throughout the brood rearing season. Worker ovary development was lowest in spring, highest in mid-summer, and intermediate in fall.     

Parasitism of an insect Manduca sexta L. alters feeding behaviour and nutrient utilization to influence developmental success of a parasitoid

The effects of macronutrient balance on nutrient intake and utilization were examined in Manduca sexta larvae parasitized by Cotesia congregata. Insects fed an artificial diet having constant total macronutrient, but with varied ratios of protein and carbohydrate, with altered diet consumption in response to excesses and deficiencies of the individual macronutrients. Bivariate plots of protein and carbohydrate consumption for non-parasitized larvae demonstrated a curvilinear relationship between points of nutrient intake for the various diets, and the larvae grew best on carbohydrate-biased diets. The relationship was linear for parasitized larvae with the growth uniform across diets. On protein-biased diets, the larvae regulated the nitrogen content, containing similar amounts of nitrogen regardless of consumption. Efficiency of nitrogen conversion in non-parasitized larvae was greatest on carbohydrate-biased diets, while nitrogen conversion by parasitized larvae was greatest with intermediate nutrient ratios. Accounting for carbohydrate consumption, the lipid content decreased as dietary carbohydrate increased, but parasitized larvae contained significantly less lipid. The total biomass of parasites developing in individual host larvae was positively correlated with host protein consumption, but the individual parasites were similar in size. Parasitism influences host nutrient consumption in a manner that achieves uniform host growth under diverse nutritional regimes, thereby constraining blood nutrient concentrations within limits suitable for parasite growth and development.     

Nutrient balance in medfly, Ceratitis capitata, larval diets affects the ability of the developing insect to incorporate lipid and protein reserves

The Mediterranean fruit fly [Ceratitis capitata Wiedemann (Diptera: Tephritidae)], or medfly, is mass produced in many facilities throughout the world to supply sterile flies for sterile insect technique programs. Production of sterile males requires large amounts of larval and adult diets. Larval diets comprise the largest economic burdens in the mass production of sterile flies, and are one of the main areas where production costs could be reduced without affecting quality and efficacy. The present study investigated the effect of manipulating diet constituents on larval development and performance. Medfly larvae were reared on diets differing in the proportions of brewer's yeast and sucrose. We studied the effect of such diets on the ability of pupating larvae to accumulate protein and lipids, and on other developmental indicators. Except for diets with a very low proportion of brewer's yeast (e.g., 4%), pupation and adult emergence rates were in general high and satisfactory. The ability of pupating larvae to accumulate lipid reserves and proteins was significantly affected by the sucrose and yeast in the diet, and by the proportion of protein to carbohydrates (P/C). In contrast to previous nutritional studies conducted with other insects, low P/C in medfly larval diets (with excess dietary carbohydrates) resulted in pupating medfly larvae having a relatively reduced load of lipids; medfly larvae protein contents in these diets were, as expected, relatively low. Similarly, high P/C ratios in the diet produced larvae with high protein and lipid contents. Differences with other insects may be due to differential post‐ingestion regulation where a high dietary carbohydrate diet reduces the lipogenic activity of the larvae, and induces a shift from lipid to glucose oxidation. Larvae reared on low P/C diets spent more time foraging in the diet than larvae maintained on a high P/C diet, suggesting a compensatory mechanism to complement nutrient intake. The results suggest that the content of brewer's yeast, the most expensive diet component, could be fine‐tuned without apparently affecting fly quality.     

Dietary self‐selection and rules of compromise by fifth‐instar Vanessa cardui

We examined dietary self‐selection and rules of compromise for protein (P) and digestible carbohydrate (C) intake by fifth‐instar Vanessa cardui L. (Lepidoptera: Nymphalidae: Nymphalini). We presented six fat‐free diet pairs to larvae in a choice trial to determine the ‘intake target’. In addition, we fed larvae seven fat‐free single diets differing in dietary nutrient ratio in no‐choice trials to determine the rules of compromise they exhibit when constrained to a singular, sub‐optimal dietary source. In choice trials, caterpillars regulated nutrient intake to a ratio of 1 protein to 1.09 carbohydrate (1P:1.09C), exhibiting tighter regulation of protein than of carbohydrate. Furthermore, larvae from different diet pair treatments did not differ in pupal mass or stadium duration. In no‐choice experiments, larvae reduced consumption on increasingly protein‐biased diets and increased consumption on increasingly carbohydrate‐biased diets, relative to a 1P:1C ratio diet. Differences in carbohydrate consumption were much greater between no‐choice treatments than differences in protein consumption. Dietary nutrient ratio affected pupal mass when accounting for initial larval mass. Pupal mass decreased as nutrient ratio was shifted off of 1P:1C, but to a greater extent when the ratio was skewed toward carbohydrate. Stadium duration increased as nutrient ratio diverged from 1P:1C, being more pronounced when shifted toward carbohydrate than toward protein. Regulation to near 1P:1C is consistent with results found for other Lepidoptera, and the rule of compromise exhibited by V. cardui is consistent with that expected for a generalist herbivore.     

Digestive enzyme profiles reveal digestive capacity and potential energy sources in fed and starved spiny lobster (Jasus edwardsii) phyllosoma larvae

The impact of starvation on the digestive enzyme (protease, trypsin, lipase and amylase) activities of Stage I and IV Jasus edwardsii phyllosoma larvae was used to identify the nutrients metabolised or conserved during food deprivation, highlighting the most critical energy reserves. Protease activities increased significantly in both Stages I and IV phyllosoma, suggesting that protein catabolism provided energy during food deprivation. Lipase activity decreased significantly in starved Stages I and IV larvae indicating that lipid may be spared for fuelling later developmental moults. The use of protein, while sparing lipid, may provide immediate energy but not at the expense of long-term lipid energy stores which are known to be important during their lengthy larval phase. The preferential use of protein during short-term periods of starvation suggests that particular attention must be given to providing sufficient protein in artificial diets at all times. Amylase activity in starved Stage I larvae was lower than in fed animals, suggesting that the starved animals are not gaining sufficient carbohydrate. However, amylase activity was similar in fed and starved Stage IV larvae, possibly due to the catabolism of accumulated glycogen stores that were not sufficiently developed in Stage I animals.     

Effects of dietary variation on growth,composition, and maturation of Manduca sexta (Sphingidae: Lepidoptera)

Most studies linking dietary variation with insect fitness focus on a single dietary component and late larval growth. We examined the effects of variation in multiple dietary factors over most life stages of the sphingid moth, Manduca sexta. Larvae received artificial diets in which protein, sucrose, and water content were varied. The relationship between larval size, growth and consumption rates differed significantly across diets. Larvae on control and low-sucrose diets grew most rapidly and attained the largest pupal and adult sizes. Conversely, larvae on low-water and low-protein diets initially grew slowly, but accelerated in the fifth instar and became pupae and adults comparable to control animals in size. There were no fundamental differences in protein:carbohydrate consumption patterns or strategies among experimental diets and larval instars. However, inadequate dietary water appeared to be more important for early than late instar larvae. Larvae on all artificial diets showed increasing fat content throughout all stages, including wandering and metamorphosis. Compensatory feeding among low-water and low-protein larvae was correlated with significantly higher fat content in larvae, pupae and adults, whereas low-sucrose animals were substantially leaner than those on the control diet. These differences may have strong effects on adult physiology, reproduction, and foraging patterns.     

The glucogenic response of a parasitized insect Manduca sexta L. is partially mediated by differential nutrient intake

Induction of gluconeogenesis is accelerated in larvae of the insect Manduca sexta L. parasitized by Cotesia congregata (Say), maintaining the concentration of the blood sugar trehalose, an important nutrient for parasite development. Investigation has demonstrated that when host larvae are offered a choice of diets with varying levels of sucrose and casein, parasitized insects consume a different balance of these nutrients, principally due to a decrease in protein consumption. The result is metabolic homeostasis, with normal unparasitized and parasitized larvae exhibiting similar levels of gluconeogenesis and blood sugar level. In the present study, normal unparasitized and parasitized larvae were maintained on individual chemically defined diets having the balance of protein and carbohydrate consumed by each when offered a dietary choice. Total dietary nutrient, the sum of carbohydrate and protein, was provided at six levels, composed of three pairs of diets. Each diet pair consisting of diets having equivalent overall nutrient ratios of 2:1 and 1:1 casein/sucrose. Host growth and diet consumption were significantly affected by dietary nutrient level and the magnitude of these effects was influenced by parasitism. Due to the effects of dietary nutrient level on diet consumption, none of the unparasitized and parasitized larvae within any of the three diet pairs consumed protein and carbohydrate at the levels predicted by the earlier choice experiments. Among insects on all of the diets, however, two groups of unparasitized and parasitized larvae consumed the expected levels of protein and carbohydrate. In each case, gluconeogenesis, as measured by 13C nuclear magnetic resonance spectroscopy (NMR) analysis of pyruvate cycling and trehalose synthesis from [2-13C]pyruvate, was evident in unparasitized and parasitized insects, confirming the conclusions of the earlier experiments. Generally, all larvae that consumed less than approximately 250 mg of sucrose over the 3-day feeding period, were gluconeogenic, regardless of diet. Differential carbohydrate consumption, therefore, was an important factor in inducing gluconeogenesis in both unparasitized and parasitized insects. The selective 13C enrichment in trehalose displayed by non-gluconeogenic larvae on some diets demonstrated trehalose formation from [2]pyruvate. The absence of net carbohydrate synthesis in these insects was likely due to an elevation of glycolysis. There was no significant effect of diet consumption or parasitism on blood trehalose level. Parasitized larvae displayed higher levels of gluconeogenesis than did unparasitized insects, a finding consistent with the conclusion that blood sugar is rapidly sequestered by developing parasites. The parasite burden, the total number of parasites developing within host larvae, as well as the number of parasites emerging from host larvae to complete development, was significantly less at the lowest dietary nutrient level, but was otherwise similar at all dietary nutrient levels. Moreover, the number of parasites that emerged increased with increasing diet consumption as reflected by host final weight.     

The effects of a harmful alga on bivalve larval lipid stores

Marine invertebrates often have complex life histories that include a swimming planktivorous larval stage, at which time they are vulnerable to a variety of stressors, including those associated with nutritional stress and harmful algal blooms. Lipid stores have been shown to be especially important for post-metamorphic survivorship and growth in a variety of marine invertebrates. We investigated the effects of the harmful brown tide alga Aureococcus anophagefferens on the lipid stores and growth of larvae of the hard clam (northern quahog, Mercenaria mercenaria), a dominant bivalve in many western Atlantic bays and estuaries. M. mercenaria was the dominant bivalve in Great South Bay, Long Island, until the mid-1970s, but very few larvae are presently found in these waters. Recent brown tide blooms have been hypothesized to pose a barrier to recovery of M. mercenaria populations and hinder recent restoration efforts by negatively affecting clam larvae. To test whether a diet of the brown tide alga affects the accumulation of beneficial lipid stores, we fed larvae one of three diets representing equal biovolumes of Isochrysis galbana, a nutritious control alga; A. anophagefferens, the brown tide alga for which nutritional quality is not presently known; or a mixture of the two. Larvae fed only brown tide had significantly less lipid stores than those in the other dietary treatments. In addition, brown tide negatively affected larval size. We also tested for evidence of tradeoffs between larval growth and lipid stores, predicting that when the diet was less nutritious as in the brown tide treatments, larval size and lipids would be negatively correlated. In contrast, we found that larvae fed a mixed algal diet or only A. anophagefferens showed a significant positive correlation between lipid stores and size, suggesting that some larvae were simply better at obtaining food and associated nutrients. Larval success likely depends on a complex interplay between genetic and environmental factors. Our study suggests that poor nutrition associated with a harmful alga can have negative effects on larval size and lipids stores, which in turn are mediated by the inter-individual variability in the ability to grow and accumulate necessary lipid stores. Phytoplankton quality is likely to be important for the sustainability of bivalve populations even when it primarily impacts the larval phase; and a diet of brown tide algae may have lasting legacies for juveniles and adults.     

Influence of dietary composition on growth and energy reserves in tench (Tinca tinca)

The effects of different protein, lipid and carbohydrate diets on growth and energy storage in tench, Tinca tinca L., were studied. Over a 2-month period fish were fed four different diets: control, protein-enriched, carbohydrate-enriched and lipid-enriched. The best growth rates were obtained with the control and protein-enriched diets; the carbohydrate diet produced the worst results (lowest specific growth rate, weight gain, nutritional index and hepatosomatic index). These results suggest that it is not advisable to reduce dietary fish protein below 35%, and that it is not possible to obtain a protein-sparing effect of either lipids or carbohydrates, at least in our experimental conditions. The high-protein diet resulted in the storage of energy excess as muscle proteins and hepatic glycogen. Tench fed the high-carbohydrate diet stored carbohydrates as muscle glycogen and reduced plasma triglycerides. Finally, both liver and muscle lipid content were in positive correlation to dietary lipid.     

The development of a synthetic diet for investigating the effects of macronutrients on the development of Plodia interpunctella

The use of chemically defined artificial diets has allowed researchers to examine questions within nutritional ecology about how macronutrients affect life‐history traits and resource‐based trade‐offs. Using a chemically defined diet, it is possible to manipulate both the total nutritional content and the ratio of macronutrients (i.e., proteins, carbohydrates, or lipids) within the diet. Studies using the geometric framework have made use of these diets to examine lifespan, fecundity, and immune responses. Here, we develop an artificial diet suitable for rearing lepidopteran larvae. We created diets with three proportions of non‐nutritive material (30, 50, and 70% indigestible cellulose) relative to protein and carbohydrate macronutrients, and compared these to standard wheat bran laboratory diet. We then examined the effects of variable nutrient content on lifespan and development time in Plodia interpunctella Hübner (Lepidoptera: Pyralidae). The artificial diets supported development (almost) as well as bran‐based laboratory diets. Total nutrient content affected development time: females that fed on the diet with the highest nutrient content took the longest time to reach eclosion. We also found evidence to support dietary restriction, with larvae receiving the fewest nutrients having the longest lifespan as adults. These findings are indicative of the usefulness of this diet as a tool to further investigate the effects of nutrient content and macronutrient imbalance on resource‐based trade‐offs and life‐history traits.     

Balancing of lipid,protein, and carbohydrate intake in a predatory beetle following hibernation,and consequences for lipid restoration

Carnivorous animals are known to balance their consumption of lipid and protein, and recent studies indicate that some mammalian carnivores also regulate their intake of carbohydrate. We investigated macronutrient balancing and lipid restoration following hibernation in the ground beetle Anchomenus dorsalis, hypothesizing that carbohydrates might be important energy sources upon hibernation when predator lipid stores are exhausted and prey are equally lean. We recorded the consumption of lipid, protein, and carbohydrate over nine days following hibernation, as the beetles foraged to refill their lipid stores. Each beetle was given the opportunity to regulate consumption from two semi-artificial foods differing in the proportion of two of the three macronutrients, while the third macronutrient was kept constant. When analyzing consumption of the three macronutrients on an energetic basis, it became apparent that the beetles regulated lipid and carbohydrate energy interchangeably and balanced the combined energy intake from the two macronutrients against protein intake. Restoration of lipid stores was independent of the availability of any specific macronutrient. However, the energetic consumption required to refill lipid stores was higher when a low proportion of lipids was ingested, suggesting that lipids were readily converted into lipid stores while there were energetic costs associated with converting carbohydrate and protein into stored lipids. Our experiment demonstrates that carbohydrates are consumed and regulated as a non-protein energy source by A. dorsalis despite an expectedly low occurrence of carbohydrates in their natural diet. Perhaps carbohydrates are in fact an overlooked supplementary energy source in the diet of carnivorous arthropods.     

Feeding behaviour and nutrient selection in an insect <Emphasis Type="Italic">Manduca sexta</Emphasis> L. and alterations induced by parasitism

Manduca sexta L. larvae exhibit broad food acceptance with regard to nutrient content during the first 3 days of the last stadium. Larvae fed diets with a constant combined level of casein and sucrose, but variable ratios, display a linear relationship between protein and carbohydrate intake. Larvae grow best on a diet with equal nutrients, but will consume an excess of one nutrient in order to obtain an adequate amount of the other, as nutrient ratio shifts. Parasitized larvae feed similarly, but the nutrient ratio does not affect growth. Unparasitized larvae regulate intake of protein and carbohydrate when offered choices of protein-biased and carbohydrate-biased diets having combined nutrient levels of 120 g/l, but with variable ratios. Larvae normally consume equal amounts of nutrients, regardless of ratio, and grow similarly. As combined nutrient level is reduced in one diet, larvae abandon regulation and feed randomly. Parasitized larvae offered choice diets with 120 g/l combined nutrients do not regulate nutrient intake. Consumption of nutrients varies widely, but growth is unaffected. Larvae offered choices of diets having equal amounts of casein and sucrose but variable fat (corn oil), fail to regulate fat intake, although both unparasitized and parasitized larvae prefer a diet containing higher fat.     

Effects of adult nutrition on female reproduction in a fruit-feeding butterfly: the role of fruit decay and dietary lipids

It was generally believed that butterflies and other holometabolous insects rely primarily on reserves accumulated during the larval stage for reproduction. Recent studies, however, highlight the often fundamental importance of adult nutrition to realize the full reproductive potential. While the importance of carbohydrates is fairly well understood, the role of most other adult-derived substances is only partially resolved. We here focus on the effects of dietary lipids (cholesterol, polyunsaturated fatty acids) and fruit decay (dietary yeast, ethanol) on female reproduction in the tropical, fruit-feeding butterfly Bicyclus anynana (Nymphalidae). We found that banana-fed control females outperformed all other groups fed on sucrose-based diets. Lipids, yeast or ethanol added to a sugar solution did not yield a similarly high reproductive output compared to fruit-fed females. Groups fed fresh or decaying banana showed no differences in reproductive performance. As we could not identify a single pivotal substance, we conclude that resource congruence (the use of nutrient types in a specified ratio) rather than any specific nutrient component is of key importance for maximum reproductive output. Further, dietary quality may affect egg hatching success in spite of no obvious effects on egg size and number. Thus, any implications about potential fitness effects of different diets need to consider egg (and hatchling) viability in addition to fecundity.     

Utilization of pre-existing energy stores of female Aedes aegypti mosquitoes during the first gonotrophic cycle

Pre-existing energy reserves may play an important role in regulating the utilization of blood meal proteins in female anautogenous mosquitoes. Determining the fate of reserves derived from the sugar meal and larval food during the first gonotrophic cycle would help to elucidate the relative contributions of larval and adult nutrition to survival and reproduction. We measured the allocation of pre-blood-meal reserves to egg production or energy production during the first gonotrophic cycle by using [14C]-labeled female Aedes aegypti mosquitoes. Feeding adults [3,4-14C]-glucose labeled the glycogen and sugar stores (approximately 50%), lipid stores (approximately 25%), and protein and amino acid stores (approximately 25%). During the first gonotrophic cycle, about 60% of the glycogen and sugar stores were metabolized and all were used for energy production. About 33% of the labeled protein and 72% of the labeled amino acid stores were metabolized, with about 9% being transferred to the eggs and the rest oxidized. About 30% of the lipid was metabolized, with about 65% being transferred to the eggs and the rest oxidized. Feeding [1-14C]-oleic acid to larvae effectively labeled adult lipid stores with about 75% of the label in lipid stores and 16% in proteins and 6% in glycogen. During the first gonotrophic cycle, about 35% of the labeled lipid stores were metabolized, with equal amounts being oxidized and transferred to the eggs. None of the other maternal stores labeled by fatty acid were metabolized during the first gonotrophic cycle. These results show that carbohydrate reserves are a critical source of energy during the first gonotrophic cycle, while lipid reserves are used equally for energy production and provisioning the eggs.     

二种改进人工饲料对红脉穗螟生长发育和繁殖的影响

在温度(29±1)℃和相对湿度75%±5%条件下,研究了2种改进人工饲料和天然饲料椰子幼果对红脉穗螟Tirathaba rufivena Walker生长发育、繁殖力和营养的影响。结果表明:与天然饲料相比,用改进人工饲料饲养的红脉穗螟幼虫生长发育速度、幼虫存活率、蛹重及产卵量均提高;幼虫相对生长率(RGR)、食物利用率(ECI)及食物转化率(ECD)均显著提高,而相对取食量(RCR)则显著降低。表明红脉穗螟幼虫对2种人工饲料有很好的适应性,可用于大量饲养。     

Effects of nutrition and density in Culex pipiens

Mosquito larvae face numerous biotic and abiotic challenges that affect their development and survivorship, as well as adult fitness. We conducted two experiments under semi‐natural conditions to evaluate the effects of intraspecific competition, nutrient limitation and sub‐lethal doses of malathion on individual life history traits in adult Culex pipiens (Diptera: Culicidae). In the first experiment, larvae of Cx. pipiens were reared at different intraspecific densities and exposed to sub‐lethal doses of malathion. In the second experiment, different intraspecific densities of Cx. pipiens larvae were reared under conditions of low or high larval nutrients, and subsequent adults were fed on either water or 10% sucrose solution. Malathion treatment had relatively minor effects compared with density, which had significant negative effects on development rate, survivorship to adulthood, body size (wing length) and longevity. As larval density increased, a sex ratio distortion in survivorship to adulthood emerged, in which a bias towards males was apparent. Nutrient‐rich larval environments alleviated, in part, the effects of increasing density and extended the lifespan of mosquitoes fed on water and 10% sucrose. Density‐dependent alterations in adult longevity attributable to the larval environment are complex and show contrasting results depending on interactions with other environmental factors. This study suggests that larval resource availability and competition influence Cx. pipiens population growth correlates and have lasting effects on traits that relate to a mosquito's ability to vector pathogens.     

Nicotine moderates the effects of macronutrient balance on nutrient intake by parasitized <Emphasis Type="Italic">Manduca sexta</Emphasis> L

Effects of dietary nicotine and macronutrient ratio on M. sexta larvae were examined. Larvae were fed a carbohydrate-biased, protein-biased or diet having equal amounts of casein and sucrose, with and without nicotine. Without nicotine, larvae displayed compensatory feeding on the low protein diet, but despite consuming more, grew least on this diet. Nicotine at 0.5% had no effect on nutrient consumption. Nicotine at 1.0 and 2.0% reduced overall consumption and thereby also reduced nicotine consumption. Larvae parasitized by C congregata displayed reduced nutrient intake and growth on all diets. Parasitized larvae responded to 1% nicotine similarly to unparasitized larvae. At 0.5% nicotine, they displayed reduced consumption on all diets, possibly due to altered chemoreceptor sensitivity to nicotine. When offered a choice of two diets having different macronutrient ratios, one with and the other without 0.1% nicotine, all larvae preferred the diet lacking nicotine and failed to regulate nutrient intake such that the nutrient intake target, a ratio of nutrients supporting optimal growth, was achieved. Parasitized larvae consumed less nicotine on a fresh weight basis than unparasitized insects, suggesting that the feeding response of parasitized larvae to nicotine minimizes the exposure of nicotine to developing parasites.     

Protein-leverage in mice: the geometry of macronutrient balancing and consequences for fat deposition

Objective: The Protein‐Leverage Hypothesis proposes that humans regulate their intake of macronutrients and that protein intake is prioritized over fat and carbohydrate intake, causing excess energy ingestion when diets contain low %protein. Here we test in a model animal, the mouse: (i) the extent to which intakes of protein and carbohydrate are regulated; (ii) if protein intake has priority over carbohydrates so that unbalanced foods low in %protein leads to increased energy intake; and (iii) how such variations in energy intake are converted into growth and storage. Methods and Procedures: We fed mice one of five isocaloric foods having different protein to carbohydrate composition, or a combination of two of these foods (N = 15). Nutrient intake and corresponding growth in lean body mass and lipid mass were measured. Data were analyzed using a geometric approach for analyzing intake of multiple nutrients. Results: (i) Mice fed different combinations of complementary foods regulated their intake of protein and carbohydrate toward a relatively well‐defined intake target. (ii) When mice were offered diets with fixed protein to carbohydrate ratio, they regulated the intake of protein more strongly than carbohydrate. This protein‐leverage resulted in higher energy consumption when diets had lower %protein and led to increased lipid storage in mice fed the diet containing the lowest %protein. Discussion: Although the protein‐leverage in mice was less than what has been proposed for humans, energy intakes were clearly higher on diets containing low %protein. This result indicates that tight protein regulation can be responsible for excess energy ingestion and higher fat deposition when the diet contains low %protein.     

Resource allocation to testes in walnut flies and implications for reproductive strategy

Testes size often predicts the winner during episodes of sperm competition. However, little is known about the source of nutrients allocated to testes development, or testes plasticity under varying nutrient availability. Among many holometabolous insects, metabolic resources can derive from the larval or adult diet. Distinguishing the source of nutrients allocated to testes can shed light on life history factors (such as maternal influences) that shape the evolution of male reproductive strategies. Here we used an experimental approach to assess resource allocation to testes development in walnut flies (Rhagoletis juglandis) from differing nutritional backgrounds. We fed adult male walnut flies on sugar and yeast diets that contrasted with the larval diet in carbon and nitrogen stable isotope ratios. This design allowed us to assess the dietary source of testes carbon and nitrogen and its change over time. We found significant incorporation of adult dietary carbon into testes, implying that walnut flies are income breeders for carbon (relying more on adult resources). In contrast, we found little evidence that walnut flies incorporate adult dietary nitrogen into testes development. We discuss the implications of these allocation decisions for life history evolution in this species.     

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.