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Tetsuo Asakura - One of the best experts on this subject based on the ideXlab platform.
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Unusual Dynamics of Alanine Residues in Polyalanine Regions with Staggered Packing Structure of Samia cynthia ricini Silk Fiber in Dry and Hydrated States Studied by 13C Solid-State NMR and Molecular Dynamics Simulation
2018Co-Authors: Akira Naito, Yugo Tasei, Akio Nishimura, Tetsuo AsakuraAbstract:Recently, the wild silkworm and spider dragline silks have been paid considerable attention as potentially valuable biomedical materials. Samia cynthia ricini is one of the wild silkworms and the primary structure of the silk fibroin (SF) consists of tandemly repeated polyalanine (poly-A:(A)12,13). Here, we report the unusual dynamical character observed in Ala Cβ groups in the poly-A region which forms an antiparallel-β-sheet structure with a staggered packing arrangement. The 13C spin–lattice relaxation (T1’s) and spin–spin relaxation times (T2’s) of Ala Cβ peaks in S. c. ricini SF fibers were observed in dry and hydrated states. The lowest field peak in Ala Cβ of the poly-A region showed 2 times longer T1 value and shorter correlation time than the other Ala Cβ peaks of the staggered packing structure, suggesting unusually fast hopping in methyl groups. Molecular dynamics simulations indicated that two of the Ala Cβ carbons out of eight existing in the unit cell of the staggered packing structure exhibited the fastest hopping motion in spite of the shortest Cβ–Cβ distance, indicating a geared hopping motion. T2 values of the hydrated and dry Ala Cβ peaks showed a similar value, indicating that the backbone motion of S. c. ricini SF fiber is not significantly affected by hydration
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Refined Crystal Structure of Samia cynthia ricini Silk Fibroin Revealed by Solid-State NMR Investigations
2017Co-Authors: Tetsuo Asakura, Akio Nishimura, Shunsuke Kametani, Shuto Kawanishi, Akihiro Aoki, Furitsu Suzuki, Hironori Kaji, Akira NaitoAbstract:Samia cynthia ricini is one of the wild silkworms and its silk fibroin (SF) consists of alternatively repeating poly-l-alanine (PLA) sequences as crystalline domain and glycine-rich sequences as noncrystalline domain; the structure is similar to those of spider silk and other wild silkworm silks. In this paper, we proposed a new staggered model for the packing arrangement of the PLA sequence through the use of the Cambridge Serial Total Energy Package program and a comparison of the observed and calculated chemical shifts of the PLA sequence with the Gauge Including Projector Augmented Wave method. The new model was supported by the interatomic distance information from the cross peaks of Ala Cβ dipolar-assisted rotational resonance (DARR) spectrum of the PLA sequences in S. c. ricini SF fiber. In addition, three 13C NMR peaks observed in the β-sheet region were assigned to the carbons with different environments in the same model, but not assigned to different β-sheet structures
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Quantitative Correlation between Primary Sequences and Conformations in 13C‑Labeled Samia cynthia ricini Silk Fibroin during Strain-Induced Conformational Transition by 13C Solid State NMR
2017Co-Authors: Tetsuo Asakura, Akio Nishimura, Yuya SatoAbstract:A better understanding of the correlation between the primary sequences and the conformations of silk fibroins (SF) is necessary in order to use silk more effectively as a functional material. In this paper, 13C CP/MAS NMR was used to monitor separately the conformational transitions of [3-13C]Ser-, [3-13C]Tyr-, and [3-13C]Ala-labeled Samia cynthia ricini SF induced by stretching. The conformation was mainly α-helix with no β-sheet structure prior to stretching. At a stretching ratio of ×5, three peaks assigned to β-sheet structure were observed, and the fraction of these peaks increased rapidly upon further stretching. In particular, a rapid increase of the fraction of β-sheet at more than ×5 stretch was observed for the Ser residues that were associated with the transition of the polyalanine chain. For the Tyr residues, the transition from random coil to β-sheet occurs independently of the transition of the crystalline domain. These correlations were quantified and may be useful in future designs of artificial silk structure
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rheological properties of native silk fibroins from domestic and wild silkworms and flow analysis in each spinneret by a finite element method
Biomacromolecules, 2009Co-Authors: Motoaki Moriya, Hitoshi Saito, Frederico Roschzttardtz, Yusuke Nakahara, Yuichi Masubuchi, Tetsuo AsakuraAbstract:Silkworms can produce strong and tough fibers at room temperature and from an aqueous solution. Therefore, it seems useful to study the mechanism of fiber formation by silkworms for development of synthetic polymers with excellent mechanical properties. The rheological behaviors of native silk dopes stored in the silk glands of Bombyx mori and Samia cynthia ricini were clarified, and flow simulations of the dopes in each spinneret were performed with a Finite Element Method. Dynamic viscoelastic measurements revealed that silk fibroin stored in silk glands forms a transient network at room temperature, and that the molecular weight for the network node corresponds to the molecular weight of a heterodimer of H-chain and L-chain (B. mori) and a homodimer of H-chains (S. c. ricini), respectively. Also, each dope exhibited zero-shear viscosity and then shear thinning like polymer melts. In addition, shear thickening due to flow-induced crystallization was observed. The critical shear rate for crystallization ...
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rheological properties of native silk fibroins from domestic and wild silkworms and flow analysis in each spinneret by a finite element method
Biomacromolecules, 2009Co-Authors: Motoaki Moriya, Hitoshi Saito, Frederico Roschzttardtz, Yusuke Nakahara, Yuichi Masubuchi, Tetsuo AsakuraAbstract:Silkworms can produce strong and tough fibers at room temperature and from an aqueous solution. Therefore, it seems useful to study the mechanism of fiber formation by silkworms for development of synthetic polymers with excellent mechanical properties. The rheological behaviors of native silk dopes stored in the silk glands of Bombyx mori and Samia cynthia ricini were clarified, and flow simulations of the dopes in each spinneret were performed with a Finite Element Method. Dynamic viscoelastic measurements revealed that silk fibroin stored in silk glands forms a transient network at room temperature, and that the molecular weight for the network node corresponds to the molecular weight of a heterodimer of H-chain and L-chain (B. mori) and a homodimer of H-chains (S. c. ricini), respectively. Also, each dope exhibited zero-shear viscosity and then shear thinning like polymer melts. In addition, shear thickening due to flow-induced crystallization was observed. The critical shear rate for crystallization of B. mori dopes was smaller than that of S. c. ricini dopes. From the flow simulation, it is suggested that domestic and wild silkworms are able to crystallize the dopes in the stiff plate region by controlling shear rate using the same magnitude of extrusion pressure despite differences in rheological properties.
Mingjie Deng - One of the best experts on this subject based on the ideXlab platform.
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comparative transcriptome analysis reveals significant metabolic alterations in eri silkworm Samia cynthia ricini haemolymph in response to 1 deoxynojirimycin
PLOS ONE, 2018Co-Authors: Shangzhi Zhang, Mingjie Deng, Dongqiong Fei, Jie Wang, Yan MengAbstract:Samia cynthia ricini (Lepidoptera: Saturniidae) is an important commercial silk-producing insect; however, in contrast to the silkworm, mulberry leaves are toxic to this insect because the leaves contain the component 1-deoxynojirimycin (DNJ). A transcriptomic analysis of eri-silkworm haemolymph was conducted to examine the genes related to different metabolic pathways and to elucidate the molecular mechanism underlying eri-silkworm haemolymph responses to DNJ. Eight hundred sixty-five differentially expressed genes (DEGs) were identified, among which 577 DEGs were up-regulated and 288 DEGs were down-regulated in the 2% DNJ group compared to control (ddH2O) after 12h. Based on the results of the functional analysis, these DEGs were associated with ribosomes, glycolysis, N-glycan biosynthesis, and oxidative phosphorylation. In particular, according to the KEGG analysis, 138 DEGs were involved in energy metabolism, glycometabolism and lipid metabolism, and the changes in the expression of nine DEGs were confirmed by reverse transcription quantitative PCR (RT-qPCR). Thus, DNJ induced significant metabolic alterations in eri-silkworm haemolymph. These results will lay the foundation for research into the toxic effects of DNJ on eri-silkworm as a model and provide a reference for the exploitation of new drugs in humans.
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metabolic changes in the midgut of eri silkworm after oral administration of 1 deoxynojirimycin a 1h nmr based metabonomic study
PLOS ONE, 2017Co-Authors: Mingjie Deng, Chao-wei Wen, Xiao-dong Lin, Min-jian Dong, Qiuting Lin, Shangzhi ZhangAbstract:1-deoxynojirimycin (DNJ) is a natural D-glucose analogue and has a strong physiological activity in inhibiting α-glucosidase in vivo. The antidiabetic effects of DNJ in mice or other mammals were extensively explored, but the physiological and toxic roles of DNJ in insects was seldom reported. In this study, the biological effects of DNJ were examined in midgut extracts of fourth-instar larvae of Eri silkworm (Samia cynthia ricini, Saturniidae). Based on nuclear magnetic resonance (NMR) metabonomics technology, we analyzed the alterations of glycometabolism, lipids, and energy metabolism pathways in the midgut of S. cynthia ricini caused by DNJ. Pattern recognition analysis (partial least square-discriminant analysis, PLS-DA) showed that four groups of latex, 0.25% DNJ, 0.5% DNJ and the mixture of 0.5% DNJ and latex (1:1) were distinctly different from the control group. Moreover, several metabolic pathways of DNJ-mediated modulation in the midgut were identified. Compared with the control group, alanine, succinate, glutamate, and fumarate concentrations decreased in three groups of 0.5% DNJ, latex, and the mixture, choline levels increased in two DNJ groups, and trehalose levels increased in all experimental groups. Therefore, these results suggest that DNJ modulated lipid metabolism by limiting the hydrolysis pathways of phospholipids metabolism. Additionally, DNJ has a potent negative effect on energy metabolism by inhibiting the hydrolysis of trehalose, glycolysis and the tricarboxylic acid (TCA) cycle. Overall, DNJ, as a single-ingredient, is an efficient substance for modulating lipid metabolism and inhibiting energy metabolism.
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An Evaluation of 1-Deoxynojirimycin Oral Administration in Eri Silkworm through Fat Body Metabolomics Based on 1H Nuclear Magnetic Resonance
Hindawi Limited, 2016Co-Authors: Chao-wei Wen, Xiao-dong Lin, Min-jian Dong, Mingjie DengAbstract:1-Deoxynojirimycin (DNJ), the main hypoglycemic constituent in mulberry (Morus alba) latex, has been extensively researched. Although there is considerable interest in the biological effects of DNJ, the roles of 1-deoxynojirimycin (DNJ) in glycometabolism and energy metabolism in insects have received little attention. In this paper, 1H nuclear magnetic resonance (1H NMR) based metabonomic was performed to study the effects of the oral supplementation of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) on the fat body glycometabolism and energy metabolism of the fourth-instar larvae of Eri silkworms, Samia cynthia ricini. Metabolic pattern recognition analysis (partial least square-discriminant analysis, PLS-DA) of fat body extracts indicated that the groups of 0.25% DNJ, 0.5% DNJ, latex, and the mixture of 0.5% DNJ and latex (1 : 1) were significantly different from the control group. Further, compared to the control group, the metabolites levels of lactate, trehalose, succinate, malate, and fumarate were remarkably changed in experimental groups, which were involved in glycolysis, hydrolysis of trehalose, and tricarboxylic acid (TCA) cycle. Our results indicate that DNJ has a positive impact on the reverse energy metabolism of Eri silkworms and metabonomic analysis based on NMR can be used as a tool to identify potential biomarkers
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a 1h nmr based study on hemolymph metabolomics in eri silkworm after oral administration of 1 deoxynojirimycin
PLOS ONE, 2015Co-Authors: Mingjie Deng, Xiao-dong Lin, Qiuting Lin, Defu Wen, Meiling Zhang, Xianqin Wang, Hongchang GaoAbstract:We aimed to investigate whether 1-deoxynojirimycin (DNJ) modulates glycometabolism and has toxicity in Eri silkworm (Samia cynthia ricini, Saturniidae). In this paper, hemolymph metabolites were used to explore metabolic changes after oral administration of DNJ or mulberry latex and to characterize the biological function of DNJ at the metabolic and systemic levels. Hemolymph samples were collected from fourth-instar larvae of Eri silkworm and ex-vivo high-resolution 1H nuclear magnetic resonance (NMR) spectra were acquired from the collected hemolymph samples. Then the obtained spectra were analyzed by principal component analysis (PCA) and independent-samples t-test. Metabolic pattern recognition analysis of hemolymph samples indicated that the groups of 0.25% DNJ, latex, and the mixture of 0.5% DNJ and latex (1:1) were significantly different from the control group. Moreover, compared to the control group, the groups of 0.25% DNJ, latex, and the mixture of 0.5% DNJ and latex (1:1) showed the decreased levels of citrate, succinate, fumarate, malate, and glutamine in hemolymph, the groups of 0.25% DNJ and the mixture of 0.5% DNJ and latex (1:1) showed the increased levels of trehalose and lactate. In addition, mulberry leaves exude latex was highly toxic to Eri silkworm because rich unidentified high-molecular-weight factor (s) acted as toxic substances. In our results, latex caused 20 deaths among 50 fourth-instar larvae of Eri silkmoth, but DNJ or the mixture did not caused death. All these results suggest that DNJ has a positive impact on the reverse glycometabolism by modulating glycometabolism and inhibiting glucogenesis and energy metabolism. DNJ is a secure substance as a single-ingredient antidiabetic medicine due to its nontoxicity and bioactivity.
Michel Pezolet - One of the best experts on this subject based on the ideXlab platform.
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protein secondary structure and orientation in silk as revealed by raman spectromicroscopy
Biophysical Journal, 2007Co-Authors: Thierry Lefevre, Marieeve Rousseau, Michel PezoletAbstract:Taking advantage of recent advances in polarized Raman microspectroscopy, and based on a rational decomposition of the amide I band, the conformation and orientation of proteins have been determined for cocoon silks of the silkworms Bombyx mori and Samia cynthia ricini and dragline silks of the spiders Nephila clavipes and Nephila edulis. This study distinguished between band components due to β-sheets, β-turns, 31-helices, and unordered structure for the four fibers. For B. mori, the β-sheet content is 50%, which matches the proportion of residues that form the GAGAGS fibroin motifs. For the Nephila dragline and S. c. ricini cocoon, the β-sheet content (36–37% and 45%, respectively) is higher than the proportion of residues that belong to polyalanine blocks (18% and 42%, respectively), showing that adjacent GGA motifs are incorporated into the β-sheets. Nephila spidroins contain fewer β-sheets and more flexible secondary structures than silkworm fibroins. The amorphous polypeptide chains are preferentially aligned parallel to the fiber direction, although their level of orientation is much lower than that of β-sheets. Overall, the results show that the four silks exhibit a common molecular organization, with mixtures of different amounts of β-sheets and flexible structures, which are organized with specific orientation levels.
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characterization by raman microspectroscopy of the strain induced conformational transition in fibroin fibers from the silkworm Samia cynthia ricini
Biomacromolecules, 2006Co-Authors: Marieeve Rousseau, Tetsuo Asakura, Thierry Lefevre, Lilyane Beaulieu, Joanie Paradis, Michel PezoletAbstract:Raman microspectroscopy has been used to quantitatively study the effect of a mechanical deformation on the conformation and orientation of Samia cynthia ricini (S. c. ricini) silk fibroin. Samples were obtained from the aqueous solution stored in the silk gland and stretched at draw ratios (lambda) ranging from 0 to 11. Using an appropriate band decomposition procedure, polarized and orientation-insensitive spectra have been analyzed to determine order parameters and the content of secondary structures, respectively. The data unambiguously show that, in response to mechanical deformation, S. c. ricini fibroin undergoes a cooperative alpha-helix to beta-sheet conformational transition above a critical draw ratio of 4. The alpha-helix content decreases from 33 to 13% when lambda increases from 0 to 11, while the amount of beta-sheets increases from 15 to 37%. In comparison, cocoon silk is devoid of alpha-helical structure and always contains a larger amount of beta-sheets. Although the presence of isosbestic points in different spectral regions reveals that the conformational change induced by mechanical deformation is a two-state process, our results suggest that part of the glycine residues might be incorporated into beta-poly(alanine) structures. The beta-sheets are initially isotropically distributed and orient along the fiber axis as lambda increases, but do not reach the high level of orientation found in the cocoon fiber. The increase in the orientation level of the beta-sheets is found to be concomitant with the alpha --> beta conformational conversion, whereas alpha-helices do not orient under the applied strain but are rather readily converted into beta-sheets. The components assigned to turns exhibit a small orientation perpendicular to the fiber axis in stretched samples, showing that, overall, the polypeptide chains are aligned along the stretching direction. Our results suggest that, in nature, factors other than stretching contribute to the optimization of the amount of beta-sheets and the high degree of orientation found in natural cocoon silk.
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study of protein conformation and orientation in silkworm and spider silk fibers using raman microspectroscopy
Biomacromolecules, 2004Co-Authors: Marieeve Rousseau, Tetsuo Asakura, Thierry Lefevre, Lilyane Beaulieu, Michel PezoletAbstract:Raman microspectroscopy has been used for the first time to determine quantitatively the orientation of the β-sheets in silk monofilaments from Bombyx mori and Samia cynthia ricini silkworms, and from the spider Nephila edulis. It is shown that, for systems with uniaxial symmetry such as silk, it is possible to determine the order parameters 〈P2〉 and 〈P4〉 of the orientation distribution function from intensity ratios of polarized Raman spectra. The equations allowing the calculation of 〈P2〉 and 〈P4〉 using polarized Raman microspectroscopy for a vibration with a cylindrical Raman tensor were first derived and then applied to the amide I band that is mostly due to the CO stretching vibration of the peptide groups. The shape of the Raman tensor for the amide I vibration of the β-sheets was determined from an isotropic film of Bombyx mori silk treated with methanol. For both the Bombyx mori and Samia cynthia ricini fibroin fibers, the values of 〈P2〉 and 〈P4〉 obtained are equal to −0.36 ± 0.03 and 0.19 ± 0.02,...
Shangzhi Zhang - One of the best experts on this subject based on the ideXlab platform.
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comparative transcriptome analysis reveals significant metabolic alterations in eri silkworm Samia cynthia ricini haemolymph in response to 1 deoxynojirimycin
PLOS ONE, 2018Co-Authors: Shangzhi Zhang, Mingjie Deng, Dongqiong Fei, Jie Wang, Yan MengAbstract:Samia cynthia ricini (Lepidoptera: Saturniidae) is an important commercial silk-producing insect; however, in contrast to the silkworm, mulberry leaves are toxic to this insect because the leaves contain the component 1-deoxynojirimycin (DNJ). A transcriptomic analysis of eri-silkworm haemolymph was conducted to examine the genes related to different metabolic pathways and to elucidate the molecular mechanism underlying eri-silkworm haemolymph responses to DNJ. Eight hundred sixty-five differentially expressed genes (DEGs) were identified, among which 577 DEGs were up-regulated and 288 DEGs were down-regulated in the 2% DNJ group compared to control (ddH2O) after 12h. Based on the results of the functional analysis, these DEGs were associated with ribosomes, glycolysis, N-glycan biosynthesis, and oxidative phosphorylation. In particular, according to the KEGG analysis, 138 DEGs were involved in energy metabolism, glycometabolism and lipid metabolism, and the changes in the expression of nine DEGs were confirmed by reverse transcription quantitative PCR (RT-qPCR). Thus, DNJ induced significant metabolic alterations in eri-silkworm haemolymph. These results will lay the foundation for research into the toxic effects of DNJ on eri-silkworm as a model and provide a reference for the exploitation of new drugs in humans.
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metabolic changes in the midgut of eri silkworm after oral administration of 1 deoxynojirimycin a 1h nmr based metabonomic study
PLOS ONE, 2017Co-Authors: Mingjie Deng, Chao-wei Wen, Xiao-dong Lin, Min-jian Dong, Qiuting Lin, Shangzhi ZhangAbstract:1-deoxynojirimycin (DNJ) is a natural D-glucose analogue and has a strong physiological activity in inhibiting α-glucosidase in vivo. The antidiabetic effects of DNJ in mice or other mammals were extensively explored, but the physiological and toxic roles of DNJ in insects was seldom reported. In this study, the biological effects of DNJ were examined in midgut extracts of fourth-instar larvae of Eri silkworm (Samia cynthia ricini, Saturniidae). Based on nuclear magnetic resonance (NMR) metabonomics technology, we analyzed the alterations of glycometabolism, lipids, and energy metabolism pathways in the midgut of S. cynthia ricini caused by DNJ. Pattern recognition analysis (partial least square-discriminant analysis, PLS-DA) showed that four groups of latex, 0.25% DNJ, 0.5% DNJ and the mixture of 0.5% DNJ and latex (1:1) were distinctly different from the control group. Moreover, several metabolic pathways of DNJ-mediated modulation in the midgut were identified. Compared with the control group, alanine, succinate, glutamate, and fumarate concentrations decreased in three groups of 0.5% DNJ, latex, and the mixture, choline levels increased in two DNJ groups, and trehalose levels increased in all experimental groups. Therefore, these results suggest that DNJ modulated lipid metabolism by limiting the hydrolysis pathways of phospholipids metabolism. Additionally, DNJ has a potent negative effect on energy metabolism by inhibiting the hydrolysis of trehalose, glycolysis and the tricarboxylic acid (TCA) cycle. Overall, DNJ, as a single-ingredient, is an efficient substance for modulating lipid metabolism and inhibiting energy metabolism.
Stefan K Hetz - One of the best experts on this subject based on the ideXlab platform.
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tradeoffs between metabolic rate and spiracular conductance in discontinuous gas exchange of Samia cynthia lepidoptera saturniidae
Journal of Insect Physiology, 2010Co-Authors: Christian Moerbitz, Stefan K HetzAbstract:Abstract The insect tracheal system is a unique respiratory system, designed for maximum oxygen delivery at high metabolic demands, e.g. during activity and at high ambient temperatures. Therefore, large safety margins are required for tracheal and spiracular conductance. Spiracles are the entry to the tracheal system and play an important role in controlling discontinuous gas exchange (DGC) between tracheal system and atmosphere in moth pupae. We investigated the effect of modulated metabolic rate (by changing ambient temperature) and modulated spiracular conductance (by blocking all except one spiracles) on gas exchange patterns in Samia pupae. Both, spiracle blocking and metabolic rates, affected respiratory behavior in Samia cynthia pupae. While animals showed discontinuous gas exchange cycles at lower temperatures with unblocked spiracles, the respiratory patterns were cyclic at higher temperatures, with partly blocked spiracles or a combination of these two factors. The threshold for the transition from a discontinuous (DGC) to a cyclic gas exchange ( cyc GE) was significantly higher in animals with unblocked spiracles (18.7 nmol g −1 min −1 vs. 7.9 nmol g −1 min −1 ). These findings indicate an important influence of spiracle conductance on the DGC, which may occur mostly in insects showing high spiracular conductances and low metabolic rates.
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control of discontinuous gas exchange in Samia cynthia effects of atmospheric oxygen carbon dioxide and moisture
The Journal of Experimental Biology, 2008Co-Authors: John S Terblanche, Stefan K Hetz, Elrike Marais, Steven L ChownAbstract:The evolution of discontinuous gas exchange (DGE) in insects is highly controversial. Adaptive hypotheses which have obtained experimental support include a water savings mechanism for living in dry environments (hygric hypothesis), a reduction in oxidative damage due to a high-performance oxygen delivery system (oxidative damage hypothesis), and the need for steep intratracheal partial pressure gradients to exchange gases under the hypercapnic and/or hypoxic conditions potentially encountered in subterranean environments (chthonic hypothesis). However, few experimental studies have simultaneously assessed multiple competing hypotheses within a strong inference framework. Here, we present such a study at the species level for a diapausing moth pupa, Samia cynthia. Switching gas conditions from controlled normoxic, normocapnic and intermediate humidity to either high or low oxygen, high or low moisture, elevated carbon dioxide, or some combination of these, revealed that DGE was abandoned under all conditions except high oxygen, and high or low gas moisture levels. Thus, support is found for the oxidative damage hypothesis when scored as maintenance of DGE. Modulation of DGE under either dry or hyperoxic conditions suggested strong support for the oxidative damage hypothesis and some limited support for the hygric hypothesis. Therefore, this study demonstrates that the DGE can be maintained and modulated in response to several environmental variables. Further investigation is required using a strong-inference, experimental approach across a range of species from different habitats to determine how widespread the support for the oxidative damage hypothesis might be.
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the role of the spiracles in gas exchange during development of Samia cynthia lepidoptera saturniidae
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2007Co-Authors: Stefan K HetzAbstract:Spiracles and the tracheal system of insects allow effective delivery of respiratory gases. During development, holometabolous insects encounter large changes in the functional morphology of gas exchange structures. To investigate changes in respiratory patterns during development, CO2-release was measured in larvae, pre-pupae and pupae of Samia cynthia (Lepidoptera, Saturniidae). Gas exchange patterns showed great variability. Caterpillars had high metabolic rates and released carbon dioxide continuously. Pre-pupae and pupae showed typical discontinuous gas exchange cycles (DGC) at reduced metabolic rates. Changes in gas exchange patterns can partly be explained with low metabolic rates during pupation. Sequential blocking of spiracles in pre-pupae and pupae reduced spiracle conductance with tracheal conductance remaining unaffected. Analysis of gas exchange patterns indicates that caterpillars and pre-pupae use more than 14 spiracles simultaneously while pupae only use 8 to 10 spiracles. Total conductance is not a simple multiple of single spiracles, but may be gradually adaptable to gas exchange demands. Surprisingly, moth pupae showed a DGC if all except one spiracle were blocked. The huge conductance of single spiracles is discussed as a pre-adaptation to high metabolic demands at the beginning and the end of the pupal as well as in the adult stage.
