Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 584
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
PLoS Comput Biol ; 17(8): e1009195, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34379622

RESUMO

Animals rely on sensory feedback to generate accurate, reliable movements. In many flying insects, strain-sensitive neurons on the wings provide rapid feedback that is critical for stable flight control. While the impacts of wing structure on aerodynamic performance have been widely studied, the impacts of wing structure on sensing are largely unexplored. In this paper, we show how the structural properties of the wing and encoding by mechanosensory neurons interact to jointly determine optimal sensing strategies and performance. Specifically, we examine how neural sensors can be placed effectively on a flapping wing to detect body rotation about different axes, using a computational wing model with varying flexural stiffness. A small set of mechanosensors, conveying strain information at key locations with a single action potential per wingbeat, enable accurate detection of body rotation. Optimal sensor locations are concentrated at either the wing base or the wing tip, and they transition sharply as a function of both wing stiffness and neural threshold. Moreover, the sensing strategy and performance is robust to both external disturbances and sensor loss. Typically, only five sensors are needed to achieve near-peak accuracy, with a single sensor often providing accuracy well above chance. Our results show that small-amplitude, dynamic signals can be extracted efficiently with spatially and temporally sparse sensors in the context of flight. The demonstrated interaction of wing structure and neural encoding properties points to the importance of understanding each in the context of their joint evolution.


Assuntos
Voo Animal/fisiologia , Insetos/anatomia & histologia , Insetos/fisiologia , Modelos Biológicos , Asas de Animais/anatomia & histologia , Asas de Animais/inervação , Potenciais de Ação/fisiologia , Animais , Evolução Biológica , Fenômenos Biomecânicos , Biologia Computacional , Simulação por Computador , Retroalimentação Sensorial/fisiologia , Manduca/anatomia & histologia , Manduca/fisiologia , Mecanorreceptores/fisiologia , Modelos Neurológicos , Rotação , Asas de Animais/fisiologia
2.
Nat Commun ; 12(1): 2867, 2021 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-34001894

RESUMO

There is now good evidence that many mutualisms evolved from antagonism; why or how, however, remains unclear. We advance the Co-Opted Antagonist (COA) Hypothesis as a general mechanism explaining evolutionary transitions from antagonism to mutualism. COA involves an eco-coevolutionary process whereby natural selection favors co-option of an antagonist to perform a beneficial function and the interacting species coevolve a suite of phenotypic traits that drive the interaction from antagonism to mutualism. To evaluate the COA hypothesis, we present a generalized eco-coevolutionary framework of evolutionary transitions from antagonism to mutualism and develop a data-based, fully ecologically-parameterized model of a small community in which a lepidopteran insect pollinates some of its larval host plant species. More generally, our theory helps to reconcile several major challenges concerning the mechanisms of mutualism evolution, such as how mutualisms evolve without extremely tight host fidelity (vertical transmission) and how ecological context influences evolutionary outcomes, and vice-versa.


Assuntos
Evolução Molecular , Insetos/genética , Plantas/genética , Simbiose/genética , Algoritmos , Animais , Datura/genética , Datura/parasitologia , Datura/fisiologia , Ecossistema , Interações Hospedeiro-Parasita/genética , Insetos/fisiologia , Manduca/genética , Manduca/fisiologia , Modelos Genéticos , Plantas/parasitologia , Polinização/genética , Polinização/fisiologia
3.
Plant Cell ; 33(5): 1748-1770, 2021 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-33561278

RESUMO

The native diploid tobacco Nicotiana attenuata produces abundant, potent anti-herbivore defense metabolites known as 17-hydroxygeranyllinalool diterpene glycosides (HGL-DTGs) whose glycosylation and malonylation biosynthetic steps are regulated by jasmonate signaling. To characterize the biosynthetic pathway of HGL-DTGs, we conducted a genome-wide analysis of uridine diphosphate glycosyltransferases (UGTs) and identified 107 family-1 UGT members. The transcript levels of three UGTs were highly correlated with the transcript levels two key HGL-DTG biosynthetic genes: geranylgeranyl diphosphate synthase (NaGGPPS) and geranyllinalool synthase (NaGLS). NaGLS's role in HGL-DTG biosynthesis was confirmed by virus-induced gene silencing. Silencing the Uridine diphosphate (UDP)-rhamnosyltransferase gene UGT91T1 demonstrated its role in the rhamnosylation of HGL-DTGs. In vitro enzyme assays revealed that UGT74P3 and UGT74P4 use UDP-glucose for the glucosylation of 17-hydroxygeranyllinalool (17-HGL) to lyciumoside I. Plants with stable silencing of UGT74P3 and UGT74P5 were severely developmentally deformed, pointing to a phytotoxic effect of the aglycone. The application of synthetic 17-HGL and silencing of the UGTs in HGL-DTG-free plants confirmed this phytotoxic effect. Feeding assays with tobacco hornworm (Manduca sexta) larvae revealed the defensive functions of the glucosylation and rhamnosylation steps in HGL-DTG biosynthesis. Glucosylation of 17-HGL is therefore a critical step that contributes to the resulting metabolites' defensive function and solves the autotoxicity problem of this potent chemical defense.


Assuntos
Monoterpenos Acíclicos/metabolismo , Diterpenos/metabolismo , Glicosídeos/metabolismo , Tabaco/metabolismo , Monoterpenos Acíclicos/química , Animais , Vias Biossintéticas , Inativação Gênica , Glicosilação , Glicosiltransferases/metabolismo , Herbivoria , Larva/fisiologia , Manduca/fisiologia , Metabolômica , Necrose , Folhas de Planta/metabolismo , Plantas Geneticamente Modificadas , Proteínas Recombinantes/metabolismo
4.
J Insect Physiol ; 130: 104201, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33582103

RESUMO

Almost all Lepidoptera produce two kinds of spermatozoa, a typical nucleated spermatozoön and an anucleate one. Inactive in the male prior to ejaculation, both of these spermatozoa become motile upon ejaculation and move to the female's sperm storage organ. This study shows that in several phylogenetically and morphologically diverse species of Lepidoptera, the anucleate spermatozoa, or parasperm (also known as apyrene spermatozoa), and the nucleated spermatozoa, or eusperm (also known as eupyrene spermatozoa), are activated by a protein of approximately 37.7 kDa added by a secretion from the male. Although proteases have been shown to activate these parasperm, inhibitors of proteases did not prevent activation of the tobacco hornworm moth, Manduca sexta, parasperm, even at well over normal working concentrations of the inhibitors. Parasperm could also be activated by an ionophore, indicating that a trans-membrane ionic event is involved. In contrast to parasperm, eusperm are first ejaculated as bundles of 256 spermatozoa. This study identified a male protein of similar molecular weight that dissociates the eusperm from the bundles, but that is sensitive to proteases. Based on these characteristics, the activators of both types of spermatozoa appear to be different from the initiatorin imputed to be the activator of commercial silkmoth, Bombyx mori, spermatozoa. The role of these proteins in these unique modes of lepidopterous sperm activation may have been adapted from other roles in other kinds of insects, and indicates especially an important function of parasperm in the reproductive physiology and/or behavior of female lepidopterans.


Assuntos
Ejaculação , Mariposas/fisiologia , Motilidade Espermática , Espermatozoides/fisiologia , Animais , Masculino , Manduca/fisiologia , Especificidade da Espécie
5.
Science ; 371(6526): 255-260, 2021 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-33446550

RESUMO

Many plant specialized metabolites function in herbivore defense, and abrogating particular steps in their biosynthetic pathways frequently causes autotoxicity. However, the molecular mechanisms underlying their defense and autotoxicity remain unclear. Here, we show that silencing two cytochrome P450s involved in diterpene biosynthesis in the wild tobacco Nicotiana attenuata causes severe autotoxicity symptoms that result from the inhibition of sphingolipid biosynthesis by noncontrolled hydroxylated diterpene derivatives. Moreover, the diterpenes' defensive function is achieved by inhibiting herbivore sphingolipid biosynthesis through postingestive backbone hydroxylation products. Thus, by regulating metabolic modifications, tobacco plants avoid autotoxicity and gain herbivore defense. The postdigestive duet that occurs between plants and their insect herbivores can reflect the plant's solutions to the "toxic waste dump" problem of using potent chemical defenses.


Assuntos
Diterpenos/metabolismo , Glucosídeos/biossíntese , Herbivoria , Manduca/fisiologia , Esfingolipídeos/biossíntese , Tabaco/metabolismo , Animais , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Hidroxilação , Manduca/enzimologia , Oxirredutases/antagonistas & inibidores , Oxirredutases/metabolismo , Tabaco/enzimologia
6.
Artigo em Inglês | MEDLINE | ID: mdl-33508422

RESUMO

An explosion of data has provided detailed information about organisms at the molecular level. For some traits, this information can accurately predict phenotype. However, knowledge of the underlying molecular networks often cannot be used to accurately predict higher order phenomena, such as the response to multiple stressors. This failure raises the question of whether methodological reductionism is sufficient to uncover predictable connections between molecules and phenotype. This question is explored in this paper by examining whether our understanding of the molecular responses to food limitation and pathogens in insects can be used to predict their combined effects. The molecular pathways underlying the response to starvation and pathogen attack in insects demonstrates the complexity of real-world physiological networks. Although known intracellular signaling pathways suggest that food restriction should enhance immune function, a reduction in food availability leads to an increase in some immune components, a decrease in others, and a complex effect on disease resistance in insects such as the caterpillar Manduca sexta. However, our inability to predict the effects of food restriction on disease resistance is likely due to our incomplete knowledge of the intra- and extracellular signaling pathways mediating the response to single or multiple stressors. Moving from molecules to organisms will require novel quantitative, integrative and experimental approaches (e.g. single cell RNAseq). Physiological networks are non-linear, dynamic, highly interconnected and replete with alternative pathways. However, that does not make them impossible to predict, given the appropriate experimental and analytical tools. Such tools are still under development. Therefore, given that molecular data sets are incomplete and analytical tools are still under development, it is premature to conclude that methodological reductionism cannot be used to predict phenotype.


Assuntos
Adaptação Fisiológica/fisiologia , Manduca/fisiologia , Animais , Larva/fisiologia
7.
Sci Robot ; 5(46)2020 09 30.
Artigo em Inglês | MEDLINE | ID: mdl-32999048

RESUMO

It is generally accepted among biology and engineering communities that insects are unstable at hover. However, existing approaches that rely on direct averaging do not fully capture the dynamical features and stability characteristics of insect flight. Here, we reveal a passive stabilization mechanism that insects exploit through their natural wing oscillations: vibrational stabilization. This stabilization technique cannot be captured using the averaging approach commonly used in literature. In contrast, it is elucidated using a special type of calculus: the chronological calculus. Our result is supported through experiments on a real hawkmoth subjected to pitch disturbance from hovering. This finding could be particularly useful to biologists because the vibrational stabilization mechanism may also be exploited by many other creatures. Moreover, our results may inspire more optimal designs for bioinspired flying robots by relaxing the feedback control requirements of flight.


Assuntos
Voo Animal/fisiologia , Insetos/fisiologia , Modelos Biológicos , Animais , Bioengenharia , Fenômenos Biofísicos , Simulação por Computador , Imageamento Tridimensional , Insetos/anatomia & histologia , Manduca/anatomia & histologia , Manduca/fisiologia , Conceitos Matemáticos , Robótica/estatística & dados numéricos , Vibração , Gravação em Vídeo , Asas de Animais/anatomia & histologia , Asas de Animais/fisiologia
8.
J Chem Ecol ; 46(10): 987-996, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32875538

RESUMO

Insect pollination is essential to many unmanaged and agricultural systems and as such is a key element in food production. However, floral scents that pollinating insects rely on to locate host plants may be altered by atmospheric oxidants, such as ozone, potentially making these cues less attractive or unrecognizable to foraging insects and decreasing pollinator efficacy. We demonstrate that levels of tropospheric ozone commonly found in many rural areas are sufficient to disrupt the innate attraction of the tobacco hawkmoth Manduca sexta to the odor of one of its preferred flowers, Nicotiana alata. However, we further find that visual navigation together with associative learning can offset this disruption. Foraging moths that initially find an ozone-altered floral scent unattractive can target an artificial flower using visual cues and associate the ozone-altered floral blend with a nectar reward. The ability to learn ozone-altered floral odors may enable pollinators to maintain communication with their co-evolutionary partners and reduce the negative impacts that anthropogenically elevated oxidants may have on plant-pollinator systems.


Assuntos
Comportamento Animal/efeitos dos fármacos , Flores/fisiologia , Manduca/fisiologia , Percepção Olfatória/efeitos dos fármacos , Ozônio/toxicidade , Tabaco/fisiologia , Animais , Flores/química , Flores/efeitos dos fármacos , Odorantes/análise , Polinização , Tabaco/efeitos dos fármacos
9.
J Chem Ecol ; 46(10): 978-986, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32876829

RESUMO

Herbivory can induce chemical changes throughout plant tissues including flowers, which could affect pollinator-pathogen interactions. Pollen is highly defended compared to nectar, but no study has examined whether herbivory affects pollen chemistry. We assessed the effects of leaf herbivory on nectar and pollen alkaloids in Nicotiana tabacum, and how herbivory-induced changes in nectar and pollen affect pollinator-pathogen interactions. We damaged leaves of Nicotiana tabacum using the specialist herbivore Manduca sexta and compared nicotine and anabasine concentrations in nectar and pollen. We then pooled nectar and pollen by collection periods (within and after one month of flowering), fed them in separate experiments to bumble bees (Bombus impatiens) infected with the gut pathogen Crithidia bombi, and assessed infections after seven days. We did not detect alkaloids in nectar, and leaf damage did not alter the effect of nectar on Crithidia counts. In pollen, herbivory induced higher concentrations of anabasine but not nicotine, and alkaloid concentrations rose and then fell as a function of days since flowering. Bees fed pollen from damaged plants had Crithidia counts 15 times higher than bees fed pollen from undamaged plants, but only when pollen was collected after one month of flowering, indicating that both damage and time since flowering affected interaction outcomes. Within undamaged treatments, bees fed late-collected pollen had Crithidia counts 10 times lower than bees fed early-collected pollen, also indicating the importance of time since flowering. Our results emphasize the role of herbivores in shaping pollen chemistry, with consequences for interactions between pollinators and their pathogens.


Assuntos
Abelhas/parasitologia , Crithidia/fisiologia , Flores/química , Herbivoria , Interações Hospedeiro-Parasita , Tabaco/química , Anabasina/análise , Animais , Comportamento Alimentar/fisiologia , Manduca/fisiologia , Nicotina/análise , Folhas de Planta/química , Néctar de Plantas/química , Pólen/química , Polinização , Fatores de Tempo
10.
Bioinspir Biomim ; 15(6): 066001, 2020 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-32924977

RESUMO

This work introduces a new biomimetic design for the well-known Wells turbine to enhance its efficiency for harvesting energy. In this paper, a biomimetic Wells turbine inspired by the geometry of hawkmoth wings is presented. Aerodynamics of both the bio-inspired design and the conventional design are investigated through computational fluid dynamics. Non-dimensional performance indicators of the bio-inspired design are compared to those of the conventional turbine, including the torque coefficient, the pressure drop coefficient, the turbine efficiency. The velocity and pressure distribution as well as the vortices shed from the blades are illustrated to understand the differences in flow phenomena. The results indicate that the biomimetic design changes the flow field and can attain a higher peak efficiency, especially at high angle of attack. Finally, the performance of blades with various aspect ratios is investigated to better understand the biomimetic design.


Assuntos
Voo Animal/fisiologia , Manduca/fisiologia , Asas de Animais/fisiologia , Animais , Fenômenos Biomecânicos , Biomimética , Simulação por Computador , Desenho de Equipamento , Modelos Biológicos , Pressão , Vento , Asas de Animais/anatomia & histologia
11.
Insect Biochem Mol Biol ; 126: 103452, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32822817

RESUMO

Although the mechanisms that control growth are now well understood, the mechanism by which animals assess their body size remains one of the great puzzles in biology. The final larval instar of holometabolous insects, after which growth stops and metamorphosis begins, is specified by a threshold size. We investigated the mechanism of threshold size assessment in the tobacco hornworm, Manduca sexta. The threshold size was found to change depending on the amount of exposure to poor nutrient conditions whereas hypoxia treatment consistently led to a lower threshold size. Under these various conditions, the mass of the muscles plus integuments was correlated with the threshold size. Furthermore, the expression of myoglianin (myo) increased at the threshold size in both M. sexta and Tribolium castaneum. Knockdown of myo in T. castaneum led to larvae that underwent supernumerary larval molts and stayed in the larval stage permanently even after passing the threshold size. We propose that increasing levels of Myo produced by the growing tissues allow larvae to assess their body size and trigger metamorphosis at the threshold size.


Assuntos
Manduca/fisiologia , Metamorfose Biológica/fisiologia , Fator de Crescimento Transformador beta/metabolismo , Animais , Tamanho Corporal/fisiologia , Técnicas de Silenciamento de Genes/métodos , Genes de Insetos , Holometábolos/crescimento & desenvolvimento , Holometábolos/fisiologia , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Larva/crescimento & desenvolvimento , Manduca/crescimento & desenvolvimento , Fator de Crescimento Transformador beta/genética , Tribolium/crescimento & desenvolvimento , Tribolium/fisiologia
12.
Int J Mol Sci ; 21(15)2020 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-32752103

RESUMO

The flight muscle of Manduca sexta (DLM1) is an emerging model system for biophysical studies of muscle contraction. Unlike the well-studied indirect flight muscle of Lethocerus and Drosophila, the DLM1 of Manduca is a synchronous muscle, as are the vertebrate cardiac and skeletal muscles. Very little has been published regarding the ultrastructure and protein composition of this muscle. Previous studies have demonstrated that DLM1 express two projectin isoform, two kettin isoforms, and two large Salimus (Sls) isoforms. Such large Sls isoforms have not been observed in the asynchronous flight muscles of Lethocerus and Drosophila. The spatial localization of these proteins was unknown. Here, immuno-localization was used to show that the N-termini of projectin and Salimus are inserted into the Z-band. Projectin spans across the I-band, and the C-terminus is attached to the thick filament in the A-band. The C-terminus of Sls was also located in the A-band. Using confocal microscopy and experimental force-length curves, thin filament lengths were estimated as ~1.5 µm and thick filament lengths were measured as ~2.5 µm. This structural information may help provide an interpretive framework for future studies using this muscle system.


Assuntos
Conectina/genética , Manduca/fisiologia , Contração Muscular/fisiologia , Proteínas Musculares/genética , Citoesqueleto de Actina/genética , Citoesqueleto de Actina/ultraestrutura , Sequência de Aminoácidos/genética , Animais , Fenômenos Biofísicos/genética , Drosophila/genética , Voo Animal/fisiologia , Manduca/genética , Contração Muscular/genética , Músculo Esquelético/fisiologia , Músculo Esquelético/ultraestrutura , Miofibrilas/genética , Miofibrilas/fisiologia , Miofibrilas/ultraestrutura , Sarcômeros/genética , Sarcômeros/fisiologia , Sarcômeros/ultraestrutura
13.
Am Nat ; 196(2): 227-240, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32673092

RESUMO

Variation in age and mass at maturity is commonly observed in populations, even among individuals with the same genetic and environmental backgrounds. Accounting for such individual variation with a stochastic model is important for estimating optimal evolutionary strategies and for understanding potential trade-offs among life-history traits. However, most studies employ stochastic models that are either phenomenological or account for variation in only one life-history trait. We propose a model based on the developmental biology of the moth Manduca sexta that accounts for stochasticity in two key life-history traits, age and mass at maturity. The model is mechanistic, describing feeding behavior and common insect developmental processes, including the degradation of juvenile hormone prior to molting. We derive a joint probability density function for the model and explore how the distribution of age and mass at maturity is affected by different parameter values. We find that the joint distribution is generally nonnormal and highly sensitive to parameter values. In addition, our model predicts previously observed effects of temperature change and nutritional quality on the expected values of insect age and mass. Our results highlight the importance of integrating multiple sources of stochasticity into life-history models.


Assuntos
Peso Corporal , Manduca/crescimento & desenvolvimento , Modelos Estatísticos , Envelhecimento , Fenômenos Fisiológicos da Nutrição Animal , Animais , Larva/crescimento & desenvolvimento , Larva/fisiologia , Traços de História de Vida , Manduca/fisiologia , Processos Estocásticos
14.
Dev Comp Immunol ; 111: 103722, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32360227

RESUMO

With a set of haemocyte specific markers novel findings on haematopoiesis in the Manduca sexta embryo are presented. We identify a hitherto unknown paired haematopoietic cluster, the abdominal haemocyte cluster in abdominal segment 7 (A7-HCC). These clusters are localised at distinct positions and are established at around katatrepsis. Later in embryogenesis, the A7-HCCs disintegrate, thereby releasing numerous embryonic plasmatocytes which disperse both anteriorly and posteriorly. These cells follow stereotypic migration routes projecting anteriorly. The thoracic larval haematopoietic organs are established at around midembryogenesis. We identify embryonic oenocytoids in the M. sexta embryo for the first time. They appear in the head region roughly at the same time as the A7-HCCs occur and successively disperse in the body cavity during development. Localisation of the prophenoloxidase (proPO) mRNA and of the proPO protein are identical. Morphological, cytometric and antigenic traits show three independently generated haemocyte types during embryogenesis.


Assuntos
Cavidade Abdominal/embriologia , Biomarcadores/metabolismo , Catecol Oxidase/genética , Precursores Enzimáticos/genética , Hemócitos/fisiologia , Proteínas de Insetos/genética , Manduca/fisiologia , Tórax/embriologia , Animais , Diferenciação Celular , Movimento Celular , Embrião não Mamífero , Desenvolvimento Embrionário , Regulação da Expressão Gênica no Desenvolvimento , Hematopoese , Proteínas de Insetos/metabolismo , Larva , Estágios do Ciclo de Vida , Organogênese
15.
Planta ; 251(4): 89, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-32232572

RESUMO

MAIN CONCLUSION: The study challenges the general belief that plants are highly sensitive to oral cues of herbivores and reveals the role of the damage level on the magnitude of defense induction. Many leaf-feeding caterpillars share similar feeding behaviors involving repeated removal of previously wounded leaf tissue (semicircle feeding pattern). We hypothesized that this behavior is a strategy to attenuate plant-induced defenses by removing both the oral cues and tissues that detect it. Using tobacco (Nicotiana tabacum) and the tobacco hornworm (Manduca sexta), we found that tobacco increased defensive responses during herbivory compared to mechanical wounding at moderate damage levels (30%). However, tobacco did not differentiate between mechanical wounding and herbivory when the level of leaf tissue loss was either small (4%) or severe (100%, whole leaf removal). Higher amounts of oral cues did not induce higher defenses when damage was small. Severe damage led to the highest level of systemic defense proteins compared to other levels of leaf tissue loss with or without oral cues. In conclusion, we did not find clear evidence that semicircle feeding behavior compromises plant defense induction. In addition, the level of leaf tissue loss and oral cues interact to determine the level of induced defensive responses in tobacco. Although oral cues play an important role in inducing defensive proteins, the level of induction depends more on the level of leaf tissue loss in tobacco.


Assuntos
Sinais (Psicologia) , Comportamento Alimentar/psicologia , Larva/fisiologia , Manduca/fisiologia , Mariposas/fisiologia , Tabaco/fisiologia , Animais , Herbivoria , Interações Hospedeiro-Parasita , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Inibidores de Proteases , Ferimentos e Lesões
16.
PLoS One ; 15(2): e0228453, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32074121

RESUMO

The late 5th instar caterpillar of the cecropia silk moth (Hyalophora cecropia) spins a silken cocoon with a distinct, multilayered architecture. The cocoon construction program, first described by the seminal work of Van der Kloot and Williams, consists of a highly ordered sequence of events. We perform behavioral experiments to re-evaluate the original cecropia work, which hypothesized that the length of silk that passes through the spinneret controls the orderly execution of each of the discrete events of cocoon spinning. We confirm and extend by three-dimensional scanning and quantitative measurements of silk weights that if cocoon construction is interrupted, upon re-spinning, the caterpillar continues the cocoon program from where it left off. We also confirm and extend by quantitative measurements of silk weights that cecropia caterpillars will not bypass any of the sections of the cocoon during the construction process, even if presented with a pre-spun section of a cocoon spun by another caterpillar. Blocking silk output inhibits caterpillars from performing normal spinning behaviors used for cocoon construction. Surprisingly, unblocking silk output 24-hr later did not restart the cocoon construction program, suggesting the involvement of a temporally-defined interval timer. We confirm with surgical reductions of the silk glands that it is the length of silk itself that matters, rather than the total amount of silk extracted by individuals. We used scanning electron microscopy to directly show that either mono- or dual-filament silk (i.e., equal silk lengths but which vary in their total amount of silk extracted) can be used to construct equivalent cocoons of normal size and that contain the relevant layers. We propose that our findings, taken together with the results of prior studies, strongly support the hypothesis that the caterpillar uses a silk "odometer" to measure the length of silk extracted during cocoon construction but does so in a temporally regulated manner. We further postulate that our examination of the anatomy of the silk spinning apparatus and ablating spinneret sensory output provides evidence that silk length measurement occurs upstream of output from the spinneret.


Assuntos
Comportamento Animal/fisiologia , Retroalimentação Sensorial/fisiologia , Manduca/fisiologia , Metamorfose Biológica/fisiologia , Seda/metabolismo , Animais , Ciências Biocomportamentais , Bombyx/anatomia & histologia , Bombyx/fisiologia , Manduca/anatomia & histologia , Microscopia Eletrônica de Varredura , Pupa/fisiologia , Sensação/fisiologia , Seda/análise , Seda/química
17.
Insect Biochem Mol Biol ; 119: 103335, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32061770

RESUMO

Life history trade-offs lead to various strategies that maximize fitness, but the developmental mechanisms underlying these alternative strategies continue to be poorly understood. In insects, trade-offs exist between size and developmental time. Recent studies in the fruit fly Drosophila melanogaster have suggested that the steroidogenic prothoracic glands play a key role in determining the timing of metamorphosis. In this study, the nutrient-dependent growth and transcriptional activation of prothoracic glands were studied in D. melanogaster and the tobacco hornworm Manduca sexta. In both species, minimum viable weight (MVW) was associated with activation of ecdysteroid biosynthesis genes and growth of prothoracic gland cells. However, the timing of MVW attainment in M. sexta is delayed by the presence of the sesquiterpenoid hormone, juvenile hormone (JH), whereas in D. melanogaster it is not. Moreover, in D. melanogaster, the transcriptional regulation of ecdysteroidogenesis becomes nutrient-independent at the MVW/critical weight (CW) checkpoint. In contrast, in M. sexta, starvation consistently reduced transcriptional activation of ecdysteroid biosynthesis genes even after CW attainment, indicating that the nature of CW differs fundamentally between the two species. In D. melanogaster, the prothoracic glands dictate the timing of metamorphosis even in the absence of nutritional inputs, whereas in M. sexta, prothoracic gland activity is tightly coupled to the nutritional status of the body, thereby delaying the onset of metamorphosis before CW attainment. We propose that selection for survival under unpredictable nutritional availability leads to the evolution of increased modularity in both morphological and endocrine traits.


Assuntos
Drosophila melanogaster/fisiologia , Ecdisteroides/metabolismo , Hormônios Juvenis/metabolismo , Traços de História de Vida , Manduca/fisiologia , Fenômenos Fisiológicos da Nutrição Animal , Animais , Peso Corporal , Drosophila melanogaster/efeitos dos fármacos , Drosophila melanogaster/crescimento & desenvolvimento , Glândulas Endócrinas/fisiologia , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Larva/fisiologia , Manduca/efeitos dos fármacos , Manduca/crescimento & desenvolvimento , Metamorfose Biológica
18.
J Chem Ecol ; 46(3): 330-343, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31989490

RESUMO

Plants perceive insect herbivores via a sophisticated surveillance system that detects a range of alarm signals, including herbivore-associated molecular patterns (HAMPs). Fatty acid-amino acid conjugates (FACs) are HAMPs present in oral secretions (OS) of lepidopteran larvae that induce defense responses in many plant species. In contrast to eggplant (Solanum melongena), tomato (S. lycopersicum) does not respond to FACs present in OS from Manduca sexta (Lepidoptera). Since both plants are found in the same genus, we tested whether loss of sensitivity to FACs in tomato may be a domestication effect. Using highly sensitive MAP kinase (MAPK) phosphorylation assays, we demonstrate that four wild tomato species and the closely related potato (S. tuberosum) do not respond to the FACs N-linolenoyl-L-glutamine and N-linolenoyl-L-glutamic acid, excluding a domestication effect. Among other genera within the Solanaceae, we found that bell pepper (Capsicum annuum) is responsive to FACs, while there is a differential responsiveness to FACs among tobacco (Nicotiana) species, ranging from strong responsiveness in N. benthamiana to no responsiveness in N. knightiana. The Petunia lineage is one of the oldest lineages within the Solanaceae and P. hybrida was responsive to FACs. Collectively, we demonstrate that plant responsiveness to FACs does not follow simple phylogenetic relationships in the family Solanaceae. Instead, sensitivity to FACs is a dynamic ancestral trait present in monocots and eudicots that was repeatedly lost during the evolution of Solanaceae species. Although tomato is insensitive to FACs, we found that other unidentified factors in M. sexta OS induce defenses in tomato.


Assuntos
Aminoácidos/metabolismo , Antibiose , Ácidos Graxos/metabolismo , Herbivoria , Manduca/fisiologia , Solanaceae/fisiologia , Animais , Larva , Especificidade da Espécie
19.
J Exp Biol ; 223(Pt 3)2020 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-31932302

RESUMO

The caterpillar Manduca sexta produces a highly stereotyped strike behavior in response to noxious thermal or mechanical stimuli to the abdomen. This rapid movement is targeted to the site of the stimulus, but the identity of the nociceptive sensory neurons are currently unknown. It is also not known whether both mechanical and thermal stimuli are detected by the same neurons. Here, we show that the likelihood of a strike increases with the strength of the stimulus and that activity in nerves innervating the body wall increases rapidly in response to noxious stimuli. Mechanical and thermal stimuli to the dorsal body wall activate the same sensory unit, suggesting it represents a multimodal neuron. This is further supported by the effects of rapidly repeated thermal or mechanical stimuli, which cause a depression of neuronal responsiveness that is generalized across modalities. Mapping the receptive fields of neurons responding to strong thermal stimuli indicates that these multimodal, nociceptive units are produced by class γ multidendritic neurons in the body wall.


Assuntos
Manduca/fisiologia , Nociceptividade , Nociceptores/fisiologia , Animais , Larva/crescimento & desenvolvimento , Larva/fisiologia , Manduca/crescimento & desenvolvimento , Estimulação Física
20.
J Comp Neurol ; 528(5): 805-815, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31644815

RESUMO

In addition to camouflage and chemical toxicity, many caterpillars defend themselves against predators with sudden sharp movements. For smaller species, these movements propel the body away from the threat, but in larger caterpillars, such as the tobacco hornworm, Manduca sexta, the movement is a defensive strike targeted to a noxious stimulus on the abdomen. Previously, strikes have been studied using mechanical stimulation like poking or pinching the insect, but such stimuli are hard to control. They also introduce mechanical perturbations that interfere with measurements of the behavior. We have now established that strike behavior can be evoked using infra-red lasers to provide a highly localized and repeatable heat stimulus. The latency from the end of an effective stimulus to the start of head movement decreased with repeated stimuli and this effect generalized to other stimulus locations indicating a centrally mediated component of sensitization. The tendency to strike increased with two successive subthreshold stimuli. When delivered to different locations or to a single site, this split-pulse stimulation revealed an additional site-specific sensitization that has not previously been described in Manduca. Previous work shows that strong stimuli increases the effectiveness of sensory stimulation by activating a long-lasting muscarinic cation current in motoneurons. Injection of muscarinic cholinergic antagonists, scopolamine methyl bromide or quinuclidinyl benzilate, only decreased the strike probability evoked by paired stimuli at two locations and not at a single site. This strongly suggests a role of muscarinic acetylcholine receptors in the generalized sensitization of nociceptive responses in caterpillars.


Assuntos
Aprendizagem da Esquiva/fisiologia , Comportamento Animal/fisiologia , Manduca/fisiologia , Nociceptividade/fisiologia , Animais , Temperatura Alta , Neurônios Motores/metabolismo , Receptores Muscarínicos/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...