Fat Body Development Research Articles

Development of the insect adult fat body relies on glycolysis, lipid synthesis, cell proliferation, and cell adhesion.

The fat body of the holometabolous insect is remodeled by the degradation of the larval fat body and the development of the adult fat body during metamorphosis. However, the mechanism of adult fat body development is quite unclear. Using the agricultural pest Helicoverpa armigera, the cotton bollworm, as a model, we revealed that the development of adult fat body was regulated by glycolysis, triglyceride (triacylglycerol [TAG]) synthesis, cell proliferation, and cell adhesion. RNA sequencing detected a set of genes that were upregulated in the 8-d late pupal fat body at a late metamorphic stage compared with the 2-d pupal fat body at an earlier metamorphic stage. The pathways for glycolysis, TAG synthesis, cell proliferation, and cell adhesion were enriched by the differentially expressed genes, and the key genes linked with these pathways showed increased expression in the 8-d pupal fat body. Knockdown of phosphofructokinase (Pfk), acetyl-CoA carboxylase (Acc1), phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit (P110) and collagen alpha-1(IV) chain (Col4a1) by RNA interference resulted in abnormal eclosion and death at pupal stages, and repressed lipid droplets accumulation and adult fat body development. The expression of Acc1, P110, and Col4a1 was repressed by the insect steroid hormone 20-hydroxyecdysone (20E). The critical genes in the 20E pathway appeared to decrease at the late pupal stage. These data suggested that the development of the insect adult fat body is regulated by glycolysis, lipids synthesis, cell proliferation, and cell adhesion at the late pupal stage when the 20E signal decreases.

Transcriptome-based analysis reveals chromatin remodeling in post-adult eclosion reconstruction of the insect fat body

The insect fat body is comparable to the liver and adipose tissue in vertebrates, and plays a pivotal role in energy metabolism, nutrient storage, and reproduction. During metamorphosis, the fat body is disassembled via programmed cell death and cell dissociation. After adult eclosion, the fat body is reconstructed either by repopulation from the remaining juvenile fat body cells or by differentiation from adult progenitor cells. This reconstruction is a prerequisite for initiating the extensive synthesis of vitellogenin (Vg), which is necessary for the maturation of eggs. Despite its significance, the underlying mechanisms of this reconstruction remain inadequately understood. Transcriptome analysis of the fat bodies from migratory locusts at 0-5 days post adult emergence revealed 79 genes associated with chromatin remodeling. Weighted gene co-expression network analysis indicated a positive correlation between chromatin remodeling and fat body reconstitution. Protein-protein interaction analysis revealed that brahma, which encodes the catalytic subunit of the SWI/SNF chromatin remodeling complex, is crucial for post-adult-eclosion fat body development. qRT-PCR analysis demonstrated that the levels of brahma mRNA in the fat body are progressively increased during the previtellogenic stage, then reach the peak and remain elevated in the vitellogenic phase. Furthermore, brahma is expressed in response to gonadotropic juvenile hormone (JH). Knockdown of brahma led to a marked reduction in Vg expression within the fat body, along with arrested ovarian growth. These findings shed light on the involvement of brahma-mediated chromatin remodeling in JH-stimulated fat body reconstruction and reproduction of adult female locusts.

Features of fat body development in the body of honey bees

The fat body is considered an organ that contains a conglomerate of proteins and fats and acts similar to the liver of mammals. It is loose tissue that is involved in some metabolic functions. One of these functions is to store and release energy in response to energy needs. The article presents data on the development of trophocytes of the fat body of the honey bee and factors that affect the process of lipolysis and lipogenesis. These processes are related to the technological methods of keeping bee colonies. The purpose of the work was to study patterns and factors that affect the growth and development of the structural elements of the fat body. For this, honeycombs with sealed brood were taken from the nest for incubation. After leaving the cells, the selected bees were placed in the nest of the bee colony. Marked bees were selected every 3 days. Histological preparations of various parts of the fat body were studied up to 21 days inclusive. According to research, trophocytes differ from enocytes in their larger size. These rounded cells have a distinct membrane and granular cytoplasm. In the cytoplasm, mostly oval-shaped vacuoles were found, which are filled with energetic and plastic substances, while others are empty. The age-related dynamics of the length of fat body trophocytes was studied. It was found that at the exit from the cell, they are the smallest and amount to an average of 50.12 ± 3.18 μm. With an increase in the activity of enzymes of the intestinal tract, an increase in the morphometric indicators of fat cells is observed. The maximum indicators of the length of trophocytes of the pericardial zone of the fat body were found in 15 daily bees. Measurement of the length of fat cells during this period shows that compared to diurnal bees, trophocytes are larger by 34.6 % (Р < 0.001). After 14 days, a gradual regression of the morphometric indicators of trophocytes is noted. The article analyzes the role of the fat body in the life of the honey bee.

A tradeoff evolution between acoustic fat bodies and skull muscles in toothed whales

Toothed whales have developed specialized echolocation abilities that are crucial for underwater activities. Acoustic fat bodies, including the melon, extramandibular fat body, and intramandibular fat body, are vital for echolocation. This study explores the transcriptome of acoustic fat bodies in toothed whales, revealing some insight into their evolutionary origins and ecological significance. Comparative transcriptome analysis of acoustic fat bodies and related tissues in a harbor porpoise and a Pacific white-sided dolphin reveals that acoustic fat bodies possess characteristics of both muscle and adipose tissue, occupying an intermediate position. The melon and extramandibular fat body exhibit specific muscle-related functions, implying an evolutionary connection between acoustic fat bodies and muscle tissue. Furthermore, we suggested that the melon and extramandibular fat body originate from intramuscular adipose tissue, a component of white adipose tissue. The extramandibular fat body has been identified as an evolutionary homolog of the masseter muscle, supported by the specific expression of MYH16, a pivotal protein in masticatory muscles. The intramandibular fat body, located within the mandibular foramen, shows possibilities of the presence of several immune-related functions, likely due to its proximity to bone marrow. Furthermore, this study sheds light on leucine modification in the catabolic pathway, which leads to the accumulation of isovaleric acid in acoustic fat bodies. Swallowing without chewing, a major toothed whale feeding ecology adaptation, makes the masticatory muscle redundant and leads to the formation of the extramandibular fat body. We propose that the intramuscular fat enlargement in facial muscles, which influences acoustic fat body development, is potentially related to the substantial reorganization of head morphology in toothed whales during aquatic adaptation.

Cell type specific polyploidization in the royal fat body of termite queens

Tissue-specific endopolyploidy is widespread among plants and animals and its role in organ development and function has long been investigated. In insects, the fat body cells of sexually mature females produce substantial amounts of egg yolk precursor proteins (vitellogenins) and exhibit high polyploid levels, which is considered crucial for boosting egg production. Termites are social insects with a reproductive division of labor, and the fat bodies of mature termite queens exhibit higher ploidy levels than those of other females. The fat bodies of mature termite queens are known to be histologically and cytologically specialized in protein synthesis. However, the relationship between such modifications and polyploidization remains unknown. In this study, we investigated the relationship among cell type, queen maturation, and ploidy levels in the fat body of the termite Reticulitermes speratus. We first confirmed that the termite fat body consists of two types of cells, that is, adipocytes, metabolically active cells, and urocytes, urate-storing cells. Our ploidy analysis using flow cytometry has shown that the fat bodies of actively reproducing queens had more polyploid cells than those of newly emerged and pre-reproductive queens, regardless of the queen phenotype (adult or neotenic type). Using image-based analysis, we found that not urocytes, but adipocytes became polyploid during queen differentiation and subsequent sexual maturation. These results suggest that polyploidization in the termite queen fat body is associated with sexual maturation and is regulated in a cell type-specific manner. Our study findings have provided novel insights into the development of insect fat bodies and provide a basis for future studies to understand the functional importance of polyploidy in the fat bodies of termite queens.

Influence of the food protein on the development of hypopharyngeal glands, fat body, quality and lifespan of honeybees

Research on the anatomical and physiological characteristics of bees (the state of fat body, hypopharyngeal glands) in connection with changes in natural and climatic conditions (soil composition, prolonged droughts, prolonged rains, cold weather, environmental disasters) impoverishment of fodder base for bees due to the decrease of sown areas of honey crops leading to the use of bees’ feeding, is relevant. The research aims to study the influence of food protein on the development of hypopharyngeal glands, fat body and life expectancy of honeybees. The zootechnical (the setting of the scientific research, the feeding of the bee families, the power of the bee families, productivity), ethological (orientation in the bee-entrance area), micrometrical (physiological and morphological characteristics of the parts of the bee’s body), microscopic (analysis of hypopharyngeal glands and fat body of bees) and statistical (biometric data processing) methods were used in the study. The significant difference in their degree of development depending on the carbohydrate or protein feeding was identified. After feeding sugar syrup to bees, signs of protein malnutrition and the state of development of hypopharyngeal glands corresponding to the І-ІІ degrees were noted. Alveoli of hypopharyngeal glands were reduced, and underdeveloped, with marked spaces, whereas after feeding protein food in the form of sugar syrup with bee pollen the bees had well-developed hypopharyngeal glands. The alveoli of the hypopharyngeal glands of the researched bees filled out, grew milky, with no space between them, and were able to produce larval food. Such a state of the glands’ development corresponds to the ІV degree of the development of hypopharyngeal glands. The research results indicate that the development of the fat body of bees happens at a young age when bees consume protein food the most. It has been proven that protein feeding of the bee colonies of experimental groups contributed to the better development of hypopharyngeal glands in both old and young bees, which resulted in better provision of food for larvae and more active development of the bee colonies. Protein feeding of bees in early spring under conditions of limited supply of protein food contributes to the production of larger larvae, which in turn contributes to the production of more complete bees

FGF signaling promotes spreading of fat body precursors necessary for adult adipogenesis in Drosophila.

Knowledge of adipogenetic mechanisms is essential to understand and treat conditions affecting organismal metabolism and adipose tissue health. In Drosophila, mature adipose tissue (fat body) exists in larvae and adults. In contrast to the well-known development of the larval fat body from the embryonic mesoderm, adult adipogenesis has remained mysterious. Furthermore, conclusive proof of its physiological significance is lacking. Here, we show that the adult fat body originates from a pool of undifferentiated mesodermal precursors that migrate from the thorax into the abdomen during metamorphosis. Through in vivo imaging, we found that these precursors spread from the ventral midline and cover the inner surface of the abdomen in a process strikingly reminiscent of embryonic mesoderm migration, requiring fibroblast growth factor (FGF) signaling as well. FGF signaling guides migration dorsally and regulates adhesion to the substrate. After spreading is complete, precursor differentiation involves fat accumulation and cell fusion that produces mature binucleate and tetranucleate adipocytes. Finally, we show that flies where adult adipogenesis is impaired by knock down of FGF receptor Heartless or transcription factor Serpent display ectopic fat accumulation in oenocytes and decreased resistance to starvation. Our results reveal that adult adipogenesis occurs de novo during metamorphosis and demonstrate its crucial physiological role.

Recruitment of Peroxin 14 to lipid droplets affects lipid storage in Drosophila.

Both peroxisomes and lipid droplets regulate cellular lipid homeostasis. Direct inter-organellar contacts as well as novel roles for proteins associated with peroxisome or lipid droplets occur when cells are induced to liberate fatty acids from lipid droplets. We have shown a non-canonical role for a subset of peroxisome-assembly [Peroxin (Pex)] proteins in this process in Drosophila. Transmembrane proteins Pex3, Pex13 and Pex14 were observed to surround newly formed lipid droplets. Trafficking of Pex14 to lipid droplets was enhanced by loss of Pex19, which directs insertion of transmembrane proteins like Pex14 into the peroxisome bilayer membrane. Accumulation of Pex14 around lipid droplets did not induce changes to peroxisome size or number, and co-recruitment of the remaining Peroxins was not needed to assemble peroxisomes observed. Increasing the relative level of Pex14 surrounding lipid droplets affected the recruitment of Hsl lipase. Fat body-specific reduction of these lipid droplet-associated Peroxins caused a unique effect on larval fat body development and affected their survival on lipid-enriched or minimal diets. This revealed a heretofore unknown function for a subset of Pex proteins in regulating lipid storage. This article has an associated First Person interview with Kazuki Ueda, joint first author of the paper.

Hygienic behavior and fat body development in worker bees (Apis mellifera L.)

Abstract. Testing for the level of manifestation of the hygienic behavior of 32 bee colonies from the local honey bee (Apis mellifera L.) from three apiaries has been carried out. Depending on the level of manifestation of the cleansing instinct, two groups of bee colonies have been formed – hygienic (these clean over 95% of the cells with dead brood up to the 48th hour after killing the brood) and non-hygienic (these clean less than 95% of the cells with dead brood up to the 48th hour). Worker bee samples have been taken from the tested bee colonies to determine the level of fat body development. The fat body is important for the bee organism, since in addition to being a fat and carbohydrate storage depot, it is also considered to be the center of metabolism in insects. The analysis of the results from the present study revealed that the mean value of the level of fat body development in worker bees from the group of hygienic bee colonies was 2.76±0.038. In the group of non-hygienic colonies this value was 7.61% lower (2.55±0.079). This difference is statistically significant at p≤0.05. Significant differences have been found in the development of the fat body in worker bees from apiaries at a distance of 100 km without regard to hygienic behavior and according to hygienic behavior. The results obtained suggest that there is a correlation between the level of fat body development and the hygienic behavior in bees.

Juvenile hormone regulates the reproductive diapause through Methoprene-tolerant gene in Galeruca daurica.

Juvenile hormone (JH) signalling plays an important role in regulation of reproductive diapause in insects. However, its underlying molecular mechanism has been unclear. Methoprene-tolerant (Met), as a universal JH receptor, is involved in JH action. To gain some insight into its function in the reproductive diapause of Galeruca daurica, a serious pest on the Inner Mongolia grasslands undergoing obligatory summer diapause at the adult stage, we cloned the complete open-reading frame (ORF) sequences of Met and other 7 JH signalling-related genes, including JH acid methyltransferase (JHAMT), JH esterase (JHE), JH epoxide hydrolase (JHEH), Krüppel homologue 1 (Kr-h1), vitellogenin (Vg), forkhead box O (FOXO) and fatty acid synthase 2 (FAS2), from this species. GdMet encoded a putative protein, which contained three domains typical of the bHLH-PAS family. Expression patterns of these eight genes were developmentally regulated during adult development. Topical application of JH analogue (JHA) methoprene into the 3-day-old and 5-day-old adults induced the expression of GdMet. Silencing GdMet by RNAi inhibited the expression of JHBP, JHE, Kr-h1 and Vg, whereas promoted the FAS2 expression, which enhanced lipid accumulation and fat body development, and finally induced the adults into diapause ahead. Combining with our previous results, we conclude that JH may regulate reproductive diapause through a conserved Met-dependent pathway in G. daurica.

Methoprene-Induced Genes in Workers of Formosan Subterranean Termites (Coptotermes formosanus Shiraki)

Termites have a distinct polyphenism controlled by concise hormonal and molecular mechanisms. Workers undergo double molts to transform into soldiers (worker–presoldier–soldier). Juvenile hormone analogs, such as methoprene, can induce workers to transform into presoldiers. However, the molecular mechanism underlying the worker-to-presoldier transformation in Coptotermes formosanus Shiraki is still not clear. We sequenced the transcriptome of workers four days after they had fed on methoprene-treated filter paper and control group workers, which fed on acetone-treated filter paper. The transcriptome of C. formosanus was assembled using the de novo assembly method. Expression levels of unigenes in the methoprene-treated group and the control group were compared. The differentially expressed genes were further analyzed by Gene Ontology (GO) term enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Tetrapyrrole binding, oxidoreductase activity, and metal ion binding were the only three enriched GO terms. Juvenile hormone synthesis was the first ranked enriched pathway. Carbohydrate, amino acid, and lipid metabolism pathways were also enriched. These three pathways may be related to fat body development, which is critical for presoldier formation. Our results have demonstrated the significance of JH synthesis pathways, and pathways related to fat body development in the artificial induction of presoldiers.

Effect of Propolis Oral Intake on Physiological Condition of Young Worker Honey Bees, Apis Mellifera L.

Abstract Honey bees collect resin from various plant species and transform it into propolis that is incorporated into the nest. The role of resins in the bee health field is poorly understood. The aim was to evaluate the effects of forced consumption of propolis on the physiological condition and short-term survival of Apis mellifera worker bees. It was tested if the number of circulating hemocytes in hemolymph, the abdominal fat bodies and the hypopharyngeal glands development were affected by the feeding with propolis extracts in laboratory conditions during the warm and the cold seasons. Propolis added to sugar candy was consumed by workers for fourteen days without affecting the bee survival. The number of circulating hemocytes in hemolymph remained constant despite the differential diet during the experiment. However, the development of fat bodies and hypopharyngeal glands was altered by propolis ingestion. The abdominal fat body development in winter bees diminished after fourteen days of propolis consumption, while it increased in summer bees. The hypopharyngeal gland development decreased for the assayed period in workers from both seasons. Our results encourage us to continue exploring this research field and learn how long-term forced ingestion of a plant-derived compound, a non-nutritive substance, can modify physiological bee parameters. A broader understanding of the multiple roles of propolis in the health of the honey bee colonies could be obtained by studying the ways in which it is processed and metabolized and the effect that generates in another physiological responses.

Summer Diapause as a Special Seasonal Adaptation in Insects: Diversity of Forms, Control Mechanisms, and Ecological Importance

Insects living in the temperate climate include summer diapause, or aestivation, in their seasonal cycle to solve various problems related to adaptation to unfavorable seasons. Unlike winter diapause, summer diapause occurs in summer and is usually terminated in autumn when active feeding, development, and/or reproduction are restored. Typically, high temperature and long day induce summer diapause and then maintain it, whereas short day and low temperature prevent induction of this diapause or terminate it. The summer diapause syndrome is basically similar to that of winter diapause; it includes prior development of large fat body, decreased level of metabolism, increased general resistance to unfavorable abiotic and biotic conditions, etc. Inhibition of morphogenesis and gametogenesis is under the control of the endocrine system. The onset of summer diapause is often accompanied by migrations to varying, sometimes significant distances to the sites of aestivation. The selective factors responsible for evolution of summer diapause vary between insect species. Climatic factors and, consequently, availability and abundance of food, as well as pressure of predators and parasites are likely to be the main factors that stimulate its occurrence. In some species, prolonged diapause begins in spring or early summer and ceases only after over-wintering. When studied in detail, such prolonged diapause often turns out to be a sequence of two independent diapauses, summer and winter ones, occurring in succession without detectable external changes.

Nutritional Signaling Regulates Vitellogenin Synthesis and Egg Development through Juvenile Hormone in Nilaparvata lugens (Stål)

Insect female reproduction which comprises the synthesis of vitellogenein (Vg) in the fat body and its incorporation into developing oocytes, needs a large amount of energy and food resources. Our previous studies found that juvenile hormone (JH) regulates vitellogenesis in the brown planthopper, Nilaparvata lugens. Here, we report on the role of JH in nutrient-regulated Vg synthesis and egg development. We first cloned the genes coding for juvenile hormone acid methyltransferase (JHAMT) which is involved in JH biosynthesis and methoprene-tolerant (Met) for JH action. Amino acids (AAs) induced the expression of jmtN, while showing no effects on the expression of met using an artificial diet culture system. Reduction in JH biosynthesis or its action by RNA interference (RNAi)-mediated silencing of jmtN or met led to a severe inhibition of AAs-induced Vg synthesis and oocyte maturation, together with lower fecundity. Furthermore, exogenous application of JH III partially restored Vg expression levels in jmtN RNAi females. However, JH III application did not rescue Vg synthesis in these met RNAi insects. Our results show that AAs induce Vg synthesis in the fat body and egg development in concert with JH biosynthesis in Nilaparvata lugens (Stål), rather than through JH action.

Fat Body Development and its Function in Energy Storage and Nutrient Sensing in Drosophila melanogaster

The fat body of Drosophila has been considered as the equivalent to the vertebrate adipose tissue and liver in its storage and major metabolic functions. It is a dynamic and multifunctional tissue which functions in energy storage, immune response and as a nutritional sensor. As a major endocrine organ in Drosophila, the fat body can produce various proteins, lipids and carbohydrates, synthesize triglyceride, diacylglycerol, trehalose and glycogen in response to energetic demands. It also secretes significant proteins governing oocyte maturation or targeting nutritional signals in the regulation of the metabolism. At different developmental stages and under different environmental conditions the fat body can interplay with other tissues in monitoring and responding to the physiological needs of the body’s growth and to coordinate the metabolism of development. The Drosophila fat body exists as a model relating to human lipometabolic disease, puberty and maturation and age-related diseases such as cancer, obesity and diabetes. In this review, we summarize the fat body formation and maturation in the Drosophila life cycle and provide an overview of fat body function as an energy reservoir and nutrient sensor. We also discuss the signaling pathways and key regulatory factors involved.

Drosophila Lipin interacts with insulin and TOR signaling pathways in the control of growth and lipid metabolism.

Lipin proteins have key functions in lipid metabolism, acting as both phosphatidate phosphatases (PAPs) and nuclear regulators of gene expression. We show that the insulin and TORC1 pathways independently control functions of Drosophila Lipin (dLipin). Reduced signaling through the insulin receptor strongly enhanced defects caused by dLipin deficiency in fat body development, whereas reduced signaling through TORC1 led to translocation of dLipin into the nucleus. Reduced expression of dLipin resulted in decreased signaling through the insulin-receptor-controlled PI3K-Akt pathway and increased hemolymph sugar levels. Consistent with this, downregulation of dLipin in fat body cell clones caused a strong growth defect. The PAP but not the nuclear activity of dLipin was required for normal insulin pathway activity. Reduction of other enzymes of the glycerol-3 phosphate pathway affected insulin pathway activity in a similar manner, suggesting an effect that is mediated by one or more metabolites associated with the pathway. Taken together, our data show that dLipin is subject to intricate control by the insulin and TORC1 pathways, and that the cellular status of dLipin impacts how fat body cells respond to signals relayed through the PI3K-Akt pathway.

Growth in weight and of some tissues in the bullfrog: fitting nonlinear models during the fattening phase

Knowledge of the growth of animals is important so that zootechnical activity can be more accurate and sustainable. The objective of this study was to describe the live weight, development of liver tissue and fat body, leg growth, and cumulative food intake of bullfrogs during the fattening phase using nonlinear models. A total of 2,375 bullfrog froglets with an initial weight of 7.03 ± 0.16 g were housed in five fattening pens (12 m²). Ten samplings were performed at intervals of 14 days to obtain the variables studied. These data were used to estimate the parameters of Gompertz and logistic models as a function of time. The estimated values of weight (Wm) and food intake (FIm) at maturity and time when the growth rate is maximum (t*) were closer to expected values when the logistic model was used. The Wm values for live weight and liver, adipose and leg weights and the FIm value for food intake were 343.7, 15.7, 19.6, 96.03 and 369.3 g, respectively, with t* at 109, 98, 105, 109 and 107 days. Therefore, the logistic model was the best model to estimate the growth and food intake of bullfrogs during the fattening phase.

Multiple regulatory safeguards confine the expression of the GATA factor Serpent to the hemocyte primordium within the Drosophila mesoderm

serpent (srp) encodes a GATA-factor that controls various aspects of embryogenesis in Drosophila, such as fatbody development, gut differentiation and hematopoiesis. During hematopoiesis, srp expression is required in the embryonic head mesoderm and the larval lymph gland, the two known hematopoietic tissues of Drosophila, to obtain mature hemocytes. srp expression in the hemocyte primordium is known to depend on snail and buttonhead, but the regulatory complexity that defines the primordium has not been addressed yet. Here, we find that srp is sufficient to transform trunk mesoderm into hemocytes. We identify two disjoint cis-regulatory modules that direct the early expression in the hemocyte primordium and the late expression in mature hemocytes and lymph gland, respectively. During embryonic hematopoiesis, a combination of snail, buttonhead, empty spiracles and even-skipped confines the mesodermal srp expression to the head region. This restriction to the head mesoderm is crucial as ectopic srp in mesodermal precursors interferes with the development of mesodermal derivates and promotes hemocytes and fatbody development. Thus, several genes work in a combined fashion to restrain early srp expression to the head mesoderm in order to prevent expansion of the hemocyte primordium.

Alimentación de dos especies de anfibios (Anura: Hylidae) en la estación de bajas temperaturas y su relación con la acumulación de energía en Santa Fe, Argentina

Feeding of two amphibian species (Anura: Hylidae) during the low temperatures season and its relationship with energy storage in Santa Fe, Argentina. In environments with thermal and pluvial seasonality such as those of the Middle Paraná River floodplain (Province of Santa Fe, Argentina), most amphibian species reproduce during the warm season and drastically diminish their activity during winter. Even though, a few species remain active during the cold season, such as Hypsiboas pulchellus that has its reproductive peak during the autumn-winter period (and the consequent energy demand). The objective of this study was to analyze and compare the feeding and development of fat bodies during the low temperature season for H. pulchellus and Dendropsophus nanus. We analyzed entire gastrointestinal tract contents of both species (H. pulchellus = 110 specimens; D. nanus = 114 specimens) and applied an index (IRI%) that combines prey abundance, volume and frequency to describe frogs diets; we used fat bodies weights as indicators of stored energy reserves. We compared diet between species with a niche overlap index (Ojk: 0-1) and used null models to ascribe statistical significance to evaluate overlap; and we analyzed variation in empty guts proportions through months and between species. Also, using ANCOVAs we explored differences in fat bodies, number and volume of prey consumed along months, between species and sexes. The most important preys in H. pulchellus diet during the cold season were Araneae (IRI% = 34.96), Chironomidae (IRI% = 33.08), Tipulidae (IRI% = 11.44) and Gryllidae (IR1% = 7.31); while for D. nanus, Chironomidae (IR1% = 48.14), Tipulidae (IRI% = 18.41), Psychodidae (IRI% = 7.44) and Araneae (IRI% = 7.34). Diet overlap between species was elevated (Ojk=0.78) and higher than expected by chance (mean simulated indices: Ojk = 0.04; p[observed > or = expected]<0.01; p[observed < or = expected] = 1). In H. pulchellus there was a monthly variation in number of prey per gut, while in D. nanus there was a difference in fat bodies development between sexes. Fat bodies development, number of prey per gut and preys volume also varied between species. Despite diet similarity between H. pulchellus and D. nanus, each species showed a different strategy to accumulate energy and support their activity during the cold season. The low rate of gastrointestinal emptiness in H. pulchellus (< 10% in any analyzed month) together with the poor development of their fat bodies, allows us to point out that, to sustain the breeding elevated energy demands, this species continues with a high feeding rate even at the low temperatures of cold season. On the other hand, the rate of gastrointestinal emptiness of D. nanus was higher than that of H. pulchellus (May = 17.24%, July = 22.22% and August = 35.71%), while their fat bodies were well developed. Thus, D. nanus would depend more on their stored reserves to sustain the energy demands of being active during the low temperatures season and hence would reach the reproductive season in spring-summer in good body condition.

Juvenile hormone regulation of Drosophila aging

BackgroundJuvenile hormone (JH) has been demonstrated to control adult lifespan in a number of non-model insects where surgical removal of the corpora allata eliminates the hormone’s source. In contrast, little is known about how juvenile hormone affects adult Drosophila melanogaster. Previous work suggests that insulin signaling may modulate Drosophila aging in part through its impact on juvenile hormone titer, but no data yet address whether reduction of juvenile hormone is sufficient to control Drosophila life span. Here we adapt a genetic approach to knock out the corpora allata in adult Drosophila melanogaster and characterize adult life history phenotypes produced by reduction of juvenile hormone. With this system we test potential explanations for how juvenile hormone modulates aging.ResultsA tissue specific driver inducing an inhibitor of a protein phosphatase was used to ablate the corpora allata while permitting normal development of adult flies. Corpora allata knockout adults had greatly reduced fecundity, inhibited oogenesis, impaired adult fat body development and extended lifespan. Treating these adults with the juvenile hormone analog methoprene restored all traits toward wildtype. Knockout females remained relatively long-lived even when crossed into a genotype that blocked all egg production. Dietary restriction further extended the lifespan of knockout females. In an analysis of expression profiles of knockout females in fertile and sterile backgrounds, about 100 genes changed in response to loss of juvenile hormone independent of reproductive state.ConclusionsReduced juvenile hormone alone is sufficient to extend the lifespan of Drosophila melanogaster. Reduced juvenile hormone limits reproduction by inhibiting the production of yolked eggs, and this may arise because juvenile hormone is required for the post-eclosion development of the vitellogenin-producing adult fat body. Our data do not support a mechanism for juvenile hormone control of longevity simply based on reducing the physiological costs of egg production. Nor does the longevity benefit appear to function through mechanisms by which dietary restriction extends longevity. We identify transcripts that change in response to juvenile hormone independent of reproductive state and suggest these represent somatically expressed genes that could modulate how juvenile hormone controls persistence and longevity.