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Urca T, Ribak G, Gefen E. Tracheal hyperallometry and spatial constraints in a large beetle. JOURNAL OF INSECT PHYSIOLOGY 2024; 155:104652. [PMID: 38777076 DOI: 10.1016/j.jinsphys.2024.104652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 05/16/2024] [Accepted: 05/16/2024] [Indexed: 05/25/2024]
Abstract
Insects exchange respiratory gases with their environment through their gas-filled tracheal system, a branched tracheal tree extending from segmental openings and terminating at fine tissue penetrating tracheoles. It was shown that the tracheal volume increases hyperallometrically with insect body size (Mb), both interspecifically and across developmental stages. In this study, we used the sixfold Mb variation in adult Batocera rufomaculata(Cerambicidae; Coleoptera) examining the allometry of adult tracheal volume (Vtr). We further explored the effect of sex and sexual maturity on tracheal gas conductance, testing the hypotheses that (i) larger body size and (ii) egg volume in gravid females would result in lower safety margins for tracheal oxygen transport due to structural restriction. We report a hyperallometric tracheal growth in both sexes of adult B. rufomaculata(mean mass exponent of 1.42 ± 0.09), similar in magnitude to previously reported values. Tracheal gas conductance was independent of Mb and reproductive state, but was significantly higher in females compared with males. We suggest that females may have pre-adapted a higher tracheal conductance required for the higher flight power output while gravid. Lack of compliant air sacs and rigid trachea may explain how gravid females retain their Vtr. However, we show that Vtr outgrows thoracic dimensions with increased B. rufomaculatasize. Hyperallometric growth of the giant cerambycid thoracic trachea could explain the previously reported hypometric scaling of flight muscles in B. rufomaculata, and the compromised long-distance flight performance of larger compared with smaller conspecifics.
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Affiliation(s)
- Tomer Urca
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
| | - Gal Ribak
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel; Steinhardt Museum of Natural History, Israel National Center for Biodiversity Studies, Tel Aviv 6997801, Israel.
| | - Eran Gefen
- Department of Biology, University of Haifa- Oranim, Kiryat Tivon, Israel
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2
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Rozen‐Rechels D, Dupoué A, Lourdais O, Chamaillé‐Jammes S, Meylan S, Clobert J, Le Galliard J. When water interacts with temperature: Ecological and evolutionary implications of thermo-hydroregulation in terrestrial ectotherms. Ecol Evol 2019; 9:10029-10043. [PMID: 31534711 PMCID: PMC6745666 DOI: 10.1002/ece3.5440] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 06/17/2019] [Indexed: 02/06/2023] Open
Abstract
The regulation of body temperature (thermoregulation) and of water balance (defined here as hydroregulation) are key processes underlying ecological and evolutionary responses to climate fluctuations in wild animal populations. In terrestrial (or semiterrestrial) ectotherms, thermoregulation and hydroregulation closely interact and combined temperature and water constraints should directly influence individual performances. Although comparative physiologists traditionally investigate jointly water and temperature regulation, the ecological and evolutionary implications of these coupled processes have so far mostly been studied independently. Here, we revisit the concept of thermo-hydroregulation to address the functional integration of body temperature and water balance regulation in terrestrial ectotherms. We demonstrate how thermo-hydroregulation provides a framework to investigate functional adaptations to joint environmental variation in temperature and water availability, and potential physiological and/or behavioral conflicts between thermoregulation and hydroregulation. We extend the classical cost-benefit model of thermoregulation in ectotherms to highlight the adaptive evolution of optimal thermo-hydroregulation strategies. Critical gaps in the parameterization of this conceptual optimality model and guidelines for future empirical research are discussed. We show that studies of thermo-hydroregulation refine our mechanistic understanding of physiological and behavioral plasticity, and of the fundamental niche of the species. This is illustrated with relevant and recent examples of space use and dispersal, resource-based trade-offs, and life-history tactics in insects, amphibians, and nonavian reptiles.
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Affiliation(s)
- David Rozen‐Rechels
- Sorbonne Université, UPEC, CNRS, IRD INRAInstitut d'Écologie et des Sciences de l'Environnement, IEESParisFrance
| | - Andréaz Dupoué
- UMR 5321 CNRS-Université Toulouse III Paul SabatierStation d'Écologie Théorique et ExpérimentaleMoulisFrance
| | - Olivier Lourdais
- UMR 7372 CNRS-ULRCentre d'Études Biologiques de ChizéVilliers en BoisFrance
- School of Life SciencesArizona State UniversityTempeAZUSA
| | - Simon Chamaillé‐Jammes
- CNRS, Univ Montpellier, EPHE, IRD, Univ Paul Valéry Montpellier 3Centre d'Écologie Fonctionnelle et ÉvolutiveMontpellierFrance
| | - Sandrine Meylan
- Sorbonne Université, UPEC, CNRS, IRD INRAInstitut d'Écologie et des Sciences de l'Environnement, IEESParisFrance
- Sorbonne UniversitéESPE de ParisParisFrance
| | - Jean Clobert
- UMR 5321 CNRS-Université Toulouse III Paul SabatierStation d'Écologie Théorique et ExpérimentaleMoulisFrance
| | - Jean‐François Le Galliard
- Sorbonne Université, UPEC, CNRS, IRD INRAInstitut d'Écologie et des Sciences de l'Environnement, IEESParisFrance
- École normale supérieure, CNRS, UMS 3194Centre de recherche en écologie expérimentale et prédictive (CEREEP‐Ecotron IleDeFrance), Département de biologiePSL Research UniversitySaint‐Pierre‐lès‐NemoursFrance
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3
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Andrew NR, Miller C, Hall G, Hemmings Z, Oliver I. Aridity and land use negatively influence a dominant species' upper critical thermal limits. PeerJ 2019; 6:e6252. [PMID: 30656070 PMCID: PMC6334740 DOI: 10.7717/peerj.6252] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 12/10/2018] [Indexed: 11/25/2022] Open
Abstract
Understanding the physiological tolerances of ectotherms, such as thermal limits, is important in predicting biotic responses to climate change. However, it is even more important to examine these impacts alongside those from other landscape changes: such as the reduction of native vegetation cover, landscape fragmentation and changes in land use intensity (LUI). Here, we integrate the observed thermal limits of the dominant and ubiquitous meat ant Iridomyrmex purpureus across climate (aridity), land cover and land use gradients spanning 270 km in length and 840 m in altitude across northern New South Wales, Australia. Meat ants were chosen for study as they are ecosystem engineers and changes in their populations may result in a cascade of changes in the populations of other species. When we assessed critical thermal maximum temperatures (CTmax) of meat ants in relation to the environmental gradients we found little influence of climate (aridity) but that CTmax decreased as LUI increased. We found no overall correlation between CTmax and CTmin. We did however find that tolerance to warming was lower for ants sampled from more arid locations. Our findings suggest that as LUI and aridification increase, the physiological resilience of I. purpureus will decline. A reduction in physiological resilience may lead to a reduction in the ecosystem service provision that these populations provide throughout their distribution.
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Affiliation(s)
- Nigel R. Andrew
- School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia
| | - Cara Miller
- School of Science and Technology, University of New England, Armidale, NSW, Australia
| | - Graham Hall
- School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia
| | - Zac Hemmings
- School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia
| | - Ian Oliver
- School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia
- Office of Environment and Heritage, Armidale, NSW, Australia
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4
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Vrtar A, Toogood C, Keen B, Beeman M, Contreras HL. The Effect of Ambient Humidity on the Metabolic Rate and Respiratory Patterns of the Hissing Cockroach, Gromphadorhina portentosa (Blattodea: Blaberidae). ENVIRONMENTAL ENTOMOLOGY 2018; 47:477-483. [PMID: 29462264 DOI: 10.1093/ee/nvx208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We examined the effects of humidity on the metabolic rates and respiratory patterns of Gromphadorhina portentosa (Schaum) (Blattodea: Blaberidae) to determine whether insects transition from continuous, cyclical, and discontinuous (DGC) respiration in response to water conservation. Eight male G. portentosa were placed under five different humidity treatments (0, 23, 40, 60, 80% RH). Using flow through respirometry we: (i) determined the effect of humidity on metabolic rate; (ii) observed if changes in metabolic rate were correlated with changes in closed/flutter (CF) or the open (O) phase of DGC; and (iii) determined whether increased spiracular closure was correlated with an increase in water retention. Although G. portentosa had similar rates of CO2 release when placed under 0, 40, 60, and 80% RH, cockroaches placed at 23% RH had a significantly higher metabolic rate. There was no effect of humidity on the duration of the CF phase of the DGC. However, the O phase of DGC was significantly longer when G. portentosa was placed at humidity levels above 23% RH. Interestingly, we saw that the average rate of mass lost to the environment did not change when cockroaches were placed at humidity levels ranging from 0 to 80% RH. This suggests that modulation of the spiracles allows G. portentosa to regulate the amount of water lost to the environment.
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Affiliation(s)
- Andrew Vrtar
- Department of Biology, University of La Verne, CA, USA
| | | | - Blake Keen
- Department of Biology, University of La Verne, CA, USA
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5
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Duncan FD, Hanrahan SA. Respiratory patterns in field collected brown locust, Locustana pardalina, in the gregarious phase. JOURNAL OF INSECT PHYSIOLOGY 2018; 106:209-216. [PMID: 29339231 DOI: 10.1016/j.jinsphys.2018.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 11/22/2017] [Accepted: 01/11/2018] [Indexed: 06/07/2023]
Abstract
In this paper we report on the metabolic rates and respiratory patterns measured from gregarious brown locusts, Locustana pardalina, collected from the Nama Karoo region in South Africa. All five instar hopper stages and adults were collected over a three year period when significant numbers of locust swarms were seen. Flow-through respirometry was used to measure the CO2 emission from individual locusts from all the developmental stages and adults within a week of collection. Carbon dioxide emission scaled hypometrically with mass, 0.863 ± 0.026. Except in the 1st and 5th instar stage there was no difference in the mass specific rate of CO2 emission (V̇<ce:small-caps>CO2</ce:small-caps>). These had significantly higher metabolic rates compared to the other stages which reflects their biology, with the 1st instar undergoing rapid growth and the 5th instar also undergoing rapid growth and development in preparation for becoming an adult. The 1st instars used a form of continuous gas exchange while all the other stages showed discontinuous gas exchange cycles. A clear burst phase and interburst periods could be seen. The 2nd and 3rd instars use mainly diffusion to expel CO2 and so exhibited an open form of the burst phase. There was an increase in CO2 volleys seen in the burst phase from the 4th instar stage onwards thus indicating an increased use of convection. There was no change in the duration or frequency of the discontinuous gas exchange cycles through the locust development or with body mass.
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Affiliation(s)
- Frances D Duncan
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, Private Bag 3, WITS 2050, South Africa.
| | - Shirley A Hanrahan
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, Private Bag 3, WITS 2050, South Africa
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Talal S, Gefen E, Ayali A. Intricate but tight coupling of spiracular activity and abdominal ventilation during locust discontinuous gas exchange cycles. ACTA ACUST UNITED AC 2018; 221:jeb.174722. [PMID: 29386224 DOI: 10.1242/jeb.174722] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 01/25/2018] [Indexed: 11/20/2022]
Abstract
Discontinuous gas exchange (DGE) is the best studied among insect gas exchange patterns. DGE cycles comprise three phases, which are defined by their spiracular state: closed, flutter and open. However, spiracle status has rarely been monitored directly; rather, it is often assumed based on CO2 emission traces. In this study, we directly recorded electromyogram (EMG) signals from the closer muscle of the second thoracic spiracle and from abdominal ventilation muscles in a fully intact locust during DGE. Muscular activity was monitored simultaneously with CO2 emission, under normoxia and under various experimental oxic conditions. Our findings indicate that locust DGE does not correspond well with the commonly described three-phase cycle. We describe unique DGE-related ventilation motor patterns, coupled to spiracular activity. During the open phase, when CO2 emission rate is highest, the thoracic spiracles do not remain open; rather, they open and close rapidly. This fast spiracle activity coincides with in-phase abdominal ventilation, while alternating with the abdominal spiracle and thus facilitating a unidirectional air flow along the main trachea. A change in the frequency of rhythmic ventilation during the open phase suggests modulation by intra-tracheal CO2 levels. A second, slow ventilatory movement pattern probably serves to facilitate gas diffusion during spiracle closure. Two flutter-like patterns are described in association with the different types of ventilatory activity. We offer a modified mechanistic model for DGE in actively ventilating insects, incorporating ventilatory behavior and changes in spiracle state.
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Affiliation(s)
- Stav Talal
- School of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Eran Gefen
- Department of Biology, University of Haifa-Oranim, Tivon 36006, Israel
| | - Amir Ayali
- School of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel.,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 6997801, Israel
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7
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Gudowska A, Schramm BW, Czarnoleski M, Kozłowski J, Bauchinger U. Physical mechanism or evolutionary trade-off? Factors dictating the relationship between metabolic rate and ambient temperature in carabid beetles. J Therm Biol 2017; 68:89-95. [DOI: 10.1016/j.jtherbio.2016.11.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 10/05/2016] [Accepted: 11/11/2016] [Indexed: 12/01/2022]
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8
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Gudowska A, Schramm BW, Czarnoleski M, Antoł A, Bauchinger U, Kozłowski J. Mass scaling of metabolic rates in carabid beetles (Carabidae) – the importance of phylogeny, regression models and gas exchange patterns. J Exp Biol 2017; 220:3363-3371. [DOI: 10.1242/jeb.159293] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 07/11/2017] [Indexed: 01/14/2023]
Abstract
The origin of the allometric relationship between standard metabolic rate (MR) and body mass (M), often described as MR=aMb, remains puzzling and interpretation of the mass-scaling exponent, b may depend on the methodological approach, shapes of residuals, coefficient of determination (r2) and sample size. We investigated the mass scaling of MRs within and between species of Carabidae beetles. We used ordinary least squares (OLS) regression, phylogenetically generalized least squares (PGLS) regression and standardized major axis (SMA) regression to explore the effects of different model-fitting methods and data clustering caused by phylogenetic clades (grade shift) and gas exchange patterns (discontinuous, cyclic and continuous). At the interspecific level, the relationship between MR and M was either negatively allometric (b<1) or isometric (b=1), depending on the fitting method. At the intraspecific level, the relationship either did not exist or was isometric or positively allometric (b>1), and the fit was significantly improved after the analysed dataset was split according to gas exchange patterns. The studied species originated from two distinct phylogenetic clades that had different intercepts but a common scaling exponent (OLS, 0.61) that was much shallower than the scaling exponent for the combined dataset for all species (OLS, 0.71). The best scaling exponent estimates were obtained by applying OLS while accounting for grade shifts or by applying PGLS. Overall, we show that allometry of MR in insects can depend heavily on the model fitting method, the structure of phylogenetic non-independence and ecological factors that elicit different modes of gas exchange.
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Affiliation(s)
- Agnieszka Gudowska
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland
| | - Bartosz W. Schramm
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland
- Sable Systems Europe GmbH, Ostendstraße 25, 12459 Berlin, Germany
| | - Marcin Czarnoleski
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland
| | - Andrzej Antoł
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland
| | - Ulf Bauchinger
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland
| | - Jan Kozłowski
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland
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9
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Talal S, Ayali A, Gefen E. An experimental evolution study confirms that discontinuous gas exchange does not contribute to body water conservation in locusts. Biol Lett 2016; 12:rsbl.2016.0807. [PMID: 28003523 DOI: 10.1098/rsbl.2016.0807] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 12/01/2016] [Indexed: 11/12/2022] Open
Abstract
The adaptive nature of discontinuous gas exchange (DGE) in insects is contentious. The classic 'hygric hypothesis', which posits that DGE serves to reduce respiratory water loss (RWL), is still the best supported. We thus focused on the hygric hypothesis in this first-ever experimental evolution study of any of the competing adaptive hypotheses. We compared populations of the migratory locust (Locusta migratoria) that underwent 10 consecutive generations of selection for desiccation resistance with control populations. Selected locusts survived 36% longer under desiccation stress but DGE prevalence did not differ between these and control populations (approx. 75%). Evolved changes in DGE properties in the selected locusts included longer cycle and interburst durations. However, in contrast with predictions of the hygric hypothesis, these changes were not associated with reduced RWL rates. Other responses observed in the selected locusts were higher body water content when hydrated and lower total evaporative water loss rates. Hence, our data suggest that DGE cycle properties in selected locusts are a consequence of an evolved increased ability to store water, and thus an improved capacity to buffer accumulated CO2, rather than an adaptive response to desiccation. We conclude that DGE is unlikely to be an evolutionary response to dehydration challenge in locusts.
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Affiliation(s)
- Stav Talal
- Department of Zoology, Tel Aviv University, Tel Aviv, Israel
| | - Amir Ayali
- Department of Zoology, Tel Aviv University, Tel Aviv, Israel
| | - Eran Gefen
- Department of Biology, University of Haifa-Oranim, Tivon, Israel
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10
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Boardman L, Sørensen JG, Koštál V, Šimek P, Terblanche JS. Cold tolerance is unaffected by oxygen availability despite changes in anaerobic metabolism. Sci Rep 2016; 6:32856. [PMID: 27619175 PMCID: PMC5020647 DOI: 10.1038/srep32856] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 08/10/2016] [Indexed: 12/18/2022] Open
Abstract
Insect cold tolerance depends on their ability to withstand or repair perturbations in cellular homeostasis caused by low temperature stress. Decreased oxygen availability (hypoxia) can interact with low temperature tolerance, often improving insect survival. One mechanism proposed for such responses is that whole-animal cold tolerance is set by a transition to anaerobic metabolism. Here, we provide a test of this hypothesis in an insect model system (Thaumatotibia leucotreta) by experimental manipulation of oxygen availability while measuring metabolic rate, critical thermal minimum (CTmin), supercooling point and changes in 43 metabolites in moth larvae at three key timepoints (before, during and after chill coma). Furthermore, we determined the critical oxygen partial pressure below which metabolic rate was suppressed (c. 4.5 kPa). Results showed that altering oxygen availability did not affect (non-lethal) CTmin nor (lethal) supercooling point. Metabolomic profiling revealed the upregulation of anaerobic metabolites and alterations in concentrations of citric acid cycle intermediates during and after chill coma exposure. Hypoxia exacerbated the anaerobic metabolite responses induced by low temperatures. These results suggest that cold tolerance of T. leucotreta larvae is not set by oxygen limitation, and that anaerobic metabolism in these larvae may contribute to their ability to survive in necrotic fruit.
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Affiliation(s)
- Leigh Boardman
- Department of Conservation Ecology and Entomology, Centre for Invasion Biology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Jesper G Sørensen
- Section for Genetics, Ecology &Evolution, Department of Bioscience, Aarhus University, Ny Munkegade 116, DK-8000 Aarhus C, Denmark
| | - Vladimír Koštál
- Institute of Entomology, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Petr Šimek
- Institute of Entomology, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czech Republic
| | - John S Terblanche
- Department of Conservation Ecology and Entomology, Centre for Invasion Biology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
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11
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Berezhkovskii AM, Shvartsman SY. Diffusive flux in a model of stochastically gated oxygen transport in insect respiration. J Chem Phys 2016; 144:204101. [PMID: 27250273 DOI: 10.1063/1.4950769] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Oxygen delivery to insect tissues is controlled by transport through a branched tubular network that is connected to the atmosphere by valve-like gates, known as spiracles. In certain physiological regimes, the spiracles appear to be randomly switching between open and closed states. Quantitative analysis of this regime leads a reaction-diffusion problem with stochastically switching boundary condition. We derive an expression for the diffusive flux at long times in this problem. Our approach starts with the derivation of the passage probability for a single particle that diffuses between a stochastically gated boundary, which models the opening and closing spiracle, and the perfectly absorbing boundary, which models oxygen absorption by the tissue. This passage probability is then used to derive an expression giving the diffusive flux as a function of the geometric parameters of the tube and characteristic time scales of diffusion and gate dynamics.
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Affiliation(s)
- Alexander M Berezhkovskii
- Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Stanislav Y Shvartsman
- Department of Chemical and Biological Engineering and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
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12
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Gudowska A, Boardman L, Terblanche JS. The closed spiracle phase of discontinuous gas exchange predicts diving duration in the grasshopper, Paracinema tricolor. J Exp Biol 2016; 219:2423-5. [DOI: 10.1242/jeb.135129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 06/04/2016] [Indexed: 11/20/2022]
Abstract
The discontinuous gas exchange (DGE) pattern of respiration shown by many arthropods includes periods of spiracle closure (C-phase) and is largely thought to serve as a physiological adaptation to restrict water loss in terrestrial environments. One major challenge to this hypothesis is to explain the presence of DGE in insects in moist environments. Here, we show a novel ecological correlate of the C-phase, namely diving behaviour in mesic Paracinema tricolor grasshoppers. Notably, maximal dive duration is positively correlated with C-phase length, even after accounting for mass scaling and absolute metabolic rate. Here, we propose that an additional advantage of DGE may be conferred by allowing the tracheal system to act as a sealed underwater oxygen reservoir. Spiracle closure may facilitate underwater submersion, which in turn, may contribute to predator avoidance, the survival of accidental immersion or periodic flooding and aid exploiting underwater resources.
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Affiliation(s)
| | - Leigh Boardman
- Department of Conservation Ecology and Entomology, Centre for Invasion Biology, Stellenbosch University, South Africa
| | - John S. Terblanche
- Department of Conservation Ecology and Entomology, Centre for Invasion Biology, Stellenbosch University, South Africa
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13
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Talal S, Ayali A, Gefen E. Discontinuous gas-exchange cycle characteristics are differentially affected by hydration state and energy metabolism in gregarious and solitary desert locusts. J Exp Biol 2015; 218:3807-15. [PMID: 26486365 DOI: 10.1242/jeb.126490] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/02/2015] [Indexed: 11/20/2022]
Abstract
The termination of discontinuous gas exchange cycles (DGCs) in severely dehydrated insects casts doubt on the generality of the hygric hypothesis, which posits that DGCs evolved as a water conservation mechanism. We followed DGC characteristics in the two density-dependent phases of the desert locust Schistocerca gregaria throughout exposure to an experimental treatment of combined dehydration and starvation stress, and subsequent rehydration. We hypothesized that, under stressful conditions, the more stress-resistant gregarious locusts would maintain DGCs longer than solitary locusts. However, we found no phase-specific variations in body water content, water loss rates (total and respiratory) or timing of stress-induced abolishment of DGCs. Likewise, locusts of both phases re-employed DGCs after ingesting comparable volumes of water when rehydrated. Despite comparable water management performances, the effect of exposure to stressful experimental conditions on DGC characteristics varied significantly between gregarious and solitary locusts. Interburst duration, which is affected by the ability to buffer CO2, was significantly reduced in dehydrated solitary locusts compared with gregarious locusts. Moreover, despite similar rehydration levels, only gregarious locusts recovered their initial CO2 accumulation capacity, indicating that cycle characteristics are affected by factors other than haemolymph volume. Haemolymph protein measurements and calculated respiratory exchange ratios suggest that catabolism of haemolymph proteins may contribute to a reduced haemolymph buffering capacity, and thus a compromised ability for CO2 accumulation, in solitary locusts. Nevertheless, DGC was lost at similar hydration states in the two phases, suggesting that DGCs are terminated as a result of inadequate oxygen supply to the tissues.
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Affiliation(s)
- Stav Talal
- Department of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Amir Ayali
- Department of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Eran Gefen
- Department of Biology, University of Haifa at Oranim, Tivon 3600600, Israel
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14
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Knight K. DGC not necessarily saving water. J Exp Biol 2015. [DOI: 10.1242/jeb.129288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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