Philip G D Matthews

University of Queensland , Brisbane, Queensland, Australia

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Publications (30)119.95 Total impact

  • Philip G D Matthews, Roger S Seymour
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    ABSTRACT: The sacred lotus Nelumbo nucifera (Gaertn.) possesses a complex system of gas canals that channel pressurised air from its leaves, down through its petioles and rhizomes, before venting this air back to the atmosphere through large stomata found in the centre of every lotus leaf. These central plate stomata (CPS) lie over a gas canal junction that connects with two-thirds of the gas canals within the leaf blade and with the larger of two discrete pairs of gas canals within the petiole that join with those in the rhizome. It is hypothesized that the lotus actively regulates the pressure, direction, and rate of airflow within its gas canals by opening and closing these stomata. Impression casting the CPS reveal that they are open in the morning, close at midday, and reopen in the afternoon. The periodic closure of the CPS during the day coincides with a temporary reversal in airflow direction within the petiolar gas canals. Experiments show that the conductance of the CPS decreases in response to increasing light level. This behaviour ventilates the rhizome and possibly directs benthic CO2 toward photosynthesis in the leaves. These results demonstrate a novel function for stomata: the active regulation of convective airflow.
    Plant Cell and Environment 07/2013; · 5.14 Impact Factor
  • N G Schimpf, P G D Matthews, C R White
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    ABSTRACT: The regulation of insect respiratory gas exchange has long been an area of interest. In particular, the reason why insects from at least five orders exhibit patterns of gas exchange that include regular periods of spiracular closure has been the source of much controversy. Three adaptive hypotheses propose that these discontinuous gas-exchange cycles (DGCs) evolved to either limit water loss across respiratory surfaces, facilitate gas exchange in underground environments or to limit oxidative damage. It is possible that DGCs evolved independently multiple times and for different reasons, but for DGCs to be a plausible target for natural selection, they must be heritable and confer a fitness benefit. In a previous study of cockroaches Nauphoeta cinerea, we demonstrated that DGCs are repeatable and extend survival under food and water restriction. Here, we show for the first time that DGCs are heritable, suggesting that they are a plausible target for natural selection.
    Journal of Evolutionary Biology 05/2013; · 3.48 Impact Factor
  • Philip G D Matthews, Craig R White
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    ABSTRACT: Many insects at rest breathe discontinuously, alternating between brief bouts of gas exchange and extended periods of breath-holding. The association between discontinuous gas exchange cycles (DGCs) and inactivity has long been recognised, leading to speculation that DGCs lie at one end of a continuum of gas exchange patterns, from continuous to discontinuous, linked to metabolic rate (MR). However, the neural hypothesis posits that it is the down-regulation of brain activity and a change in the neural control of gas exchange, rather than low MR per se, which is responsible for the emergence of DGCs during inactivity. To test this, cockroaches Nauphoeta cinerea had their brains inactivated by applying a Peltier-chilled cold probe to the head. Once brain temperature fell to 8°C cockroaches switched from a continuous to a discontinuous breathing pattern. Re-warming the brain abolished the DGC and re-established a continuous breathing pattern. Chilling the brain did not significantly reduce the cockroaches' MR and there was no association between the gas exchange pattern displayed by the insect and its MR. This demonstrates that DGCs can arise due to a decrease in brain activity and a change in the underlying regulation of gas exchange, and are not necessarily a simple consequence of low respiratory demand.
    Journal of Experimental Biology 02/2013; · 3.24 Impact Factor
  • Lucy Merritt, Philip G D Matthews, Craig R White
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    ABSTRACT: Resting metabolic rates can vary greatly between individuals of the same species. These differences are generally repeatable and show moderate-to-high heritability, suggesting that they could be a target for natural selection. The present study therefore aimed to determine if inter-individual differences in resting metabolic rates (RMR) in garden skinks Lampropholis delicata were associated with inter-individual differences in a suite of physiological and behavioural variables: aerobic capacity, burst sprinting speed and thermal preference. Whole-animal measures of aerobic capacity and RMR were significantly positively correlated, but mass-independent measures were not. Burst sprinting speed and thermal preference were also not correlated with RMR.
    Journal of Comparative Physiology B 01/2013; · 2.02 Impact Factor
  • Roger S Seymour, Philip G D Matthews
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    ABSTRACT: Insects and spiders rely on gas-filled airways for respiration in air. However, some diving species take a tiny air-store bubble from the surface that acts as a primary O(2) source and also as a physical gill to obtain dissolved O(2) from the water. After a long history of modelling, recent work with O(2)-sensitive optodes has tested the models and extended our understanding of physical gill function. Models predict that compressible gas gills can extend dives up to more than eightfold, but this is never reached, because the animals surface long before the bubble is exhausted. Incompressible gas gills are theoretically permanent. However, neither compressible nor incompressible gas gills can support even resting metabolic rate unless the animal is very small, has a low metabolic rate or ventilates the bubble's surface, because the volume of gas required to produce an adequate surface area is too large to permit diving. Diving-bell spiders appear to be the only large aquatic arthropods that can have gas gill surface areas large enough to supply resting metabolic demands in stagnant, oxygenated water, because they suspend a large bubble in a submerged web.
    Journal of Experimental Biology 01/2013; 216(Pt 2):164-70. · 3.24 Impact Factor
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    Natalie G Schimpf, Philip G D Matthews, Craig R White
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    ABSTRACT: Metabolic rate varies significantly between individuals, and these differences persist even when the wide range of biotic and abiotic factors that influence metabolism are accounted for. It is important to understand the life history implications of variation in metabolic rate, but they remain poorly characterised despite a growing body of work examining relationships between metabolism and a range of traits. In the present study we used laboratory-bred families (one sire to three dams) of Nauphoeta cinerea (Olivier) (speckled cockroaches) to examine the relationship between standard metabolic rate (SMR) and reproductive performance (number of offspring and gestation duration). We show that SMR is negatively associated with female gestation duration. Age at mating is negatively associated with gestation duration for females, and mass is negatively associated with the average gestation duration of the females a male was mated with. In addition to the results in the current literature, the results from the present study suggest that the association between metabolism and life history is more complex than simple relationships between metabolism and various fitness traits. Future work should consider longitudinal, ontogenetic as well as selective and quantitative genetic breeding approaches to fully examine the associations between metabolism and fitness.
    Biology open. 12/2012; 1(12):1185-91.
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    ABSTRACT: Weibel and Taylor's theory of symmorphosis predicts that the structural components of the respiratory system are quantitatively adjusted to satisfy, but not exceed, an animal's maximum requirement for oxygen. We tested this in the respiratory system of the adult migratory locust Locusta migratoria by comparing the aerobic capacity of hopping and flight muscle with the morphology of the oxygen cascade. Maximum oxygen uptake by flight muscle during tethered flight is 967±76 μmol h(-1) g(-1) (body mass specific, ±95% confidence interval CI), whereas the hopping muscles consume a maximum of 158±8 μmol h(-1) g(-1) during jumping. The 6.1-fold difference in aerobic capacity between the two muscles is matched by a 6.4-fold difference in tracheole lumen volume, which is 3.5×10(8)±1.2×10(8) μm(3) g(-1) in flight muscle and 5.5×10(7)±1.8×10(7) μm(3) g(-1) in the hopping muscles, a 6.4-fold difference in tracheole inner cuticle surface area, which is 3.2×10(9)±1.1×10(9) μm(2) g(-1) in flight muscle and 5.0×10(8)±1.7×10(8) μm(2) g(-1) in the hopping muscles, and a 6.8-fold difference in tracheole radial diffusing capacity, which is 113±47 μmol kPa(-1) h(-1) g(-1) in flight muscle and 16.7±6.5 μmol kPa(-1) h(-1) g(-1) in the hopping muscles. However, there is little congruence between the 6.1-fold difference in aerobic capacity and the 19.8-fold difference in mitochondrial volume, which is 3.2×10(10)±3.9×10(9) μm(3) g(-1) in flight muscle and only 1.6×10(9)±1.4×10(8) μm(3) g(-1) in the hopping muscles. Therefore, symmorphosis is upheld in the design of the tracheal system, but not in relation to the amount of mitochondria, which might be due to other factors operating at the molecular level.
    Journal of Experimental Biology 06/2012; 215(Pt 18):3324-33. · 3.24 Impact Factor
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    ABSTRACT: Flying insects achieve the highest mass-specific aerobic metabolic rates of all animals. However, few studies attempt to maximise the metabolic cost of flight and so many estimates could be sub-maximal, especially where insects have been tethered. To address this issue, oxygen consumption was measured during tethered flight in adult locusts Locusta migratoria, some of which had a weight attached to each wing (totalling 30-45% of body mass). Mass-specific metabolic rate increased from 28±2 μmol O(2) g(-1) h(-1) at rest to 896±101 μmol O(2)g(-1) h(-1) during flight in weighted locusts, and to 1032±69 μmol O(2) g(-1) h(-1) in unweighted locusts. Maximum metabolic rate of locusts during tethered flight (m(O(2)); μmol O(2) h(-1)) increased with body mass (M(b); g) according to the allometric equation m(O(2))=994M(b)(0.75±0.19), whereas published metabolic rates of moths and orchid bees during hovering free flight (h(O(2))) are approximately 2.8-fold higher, h(O(2))=2767M(b)(0.72±0.08). The modest flight metabolic rate of locusts is unlikely to be an artefact of individuals failing to exert themselves, because mean maximum lift was not significantly different from that required to support body mass (95±8%), mean wingbeat frequency was 23.7±0.6 Hz, and mean stroke amplitude was 105±5 deg in the forewing and 96±5 deg in the hindwing - all of which are close to free-flight values. Instead, the low cost of flight could reflect the relatively small size and relatively modest anatomical power density of the locust flight motor, which is a likely evolutionary trade-off between flight muscle maintenance costs and aerial performance.
    Journal of Experimental Biology 06/2012; 215(Pt 18):3317-23. · 3.24 Impact Factor
  • Edward P Snelling, Philip G D Matthews, Roger S Seymour
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    ABSTRACT: The discontinuous gas exchange cycle (DGC) is a three-phase breathing pattern displayed by many insects at rest. The pattern consists of an extended breath-hold period (closed phase), followed by a sequence of rapid gas exchange pulses (flutter phase), and then a period in which respiratory gases move freely between insect and environment (open phase). This study measured CO(2) emission in resting locusts Locusta migratoria throughout ontogeny, in normoxia (21 kPa P(O2)), hypoxia (7 kPa P(O2)) and hyperoxia (40 kPa P(O2)), to determine whether body mass and ambient O(2) affect DGC phase duration. In normoxia, mean CO(2) production rate scales with body mass (M(b); g) according to the allometric power equation , closed phase duration (C; min) scales with body mass according to the equation C=8.0M(b)(0.38±0.29), closed+flutter period (C+F; min) scales with body mass according to the equation C+F=26.6M (0.20±0.25)(b) and open phase duration (O; min) scales with body mass according to the equation O=13.3M(b) (0.23±0.18). Hypoxia results in a shorter C phase and longer O phase across all life stages, whereas hyperoxia elicits shorter C, C+F and O phases across all life stages. The tendency for larger locusts to exhibit longer C and C+F phases might arise if the positive allometric scaling of locust tracheal volume prolongs the time taken to reach the minimum O(2) and maximum CO(2) set-points that determine the duration of these respective periods, whereas an increasingly protracted O phase could reflect the additional time required for larger locusts to expel CO(2) through a relatively longer tracheal pathway. Observed changes in phase duration under hypoxia possibly serve to maximise O(2) uptake from the environment, whereas the response of the DGC to hyperoxia is difficult to explain, but could be affected by elevated levels of reactive oxygen species.
    Journal of Experimental Biology 06/2012; 215(Pt 19):3388-93. · 3.24 Impact Factor
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    ABSTRACT: While O(2)-binding hemoglobin-like proteins are present in many insects, prominent amounts of hemoglobin have only been found in a few species. Backswimmers of the genera Anisops and Buenoa (Notonectidae) have high concentrations of hemoglobin in the large tracheal cells of the abdomen. Oxygen from the hemoglobin is delivered to a gas bubble and controls the buoyant density, which enables the bugs to maintain their position without swimming and to remain stationary in the mid-water zone where they hunt for prey. We have obtained the cDNA sequences of three Anisops deanei hemoglobin chains by RT-PCR and RACE techniques. The deduced amino acid sequences show an unusual insertion of a single amino acid in the conserved helix E, but this does not affect protein stability or ligand binding kinetics. Recombinant A. deanei hemoglobin has an oxygen affinity of P(50) = 2.4 kPa (18 torr) and reveals the presence of a dimeric fraction or two different conformations. The absorption spectra demonstrate that the Anisops hemoglobin is a typical pentacoordinate globin. Phylogenetic analyses show that the backswimmer hemoglobins evolved within Heteroptera and most likely originated from an intracellular hemoglobin with divergent function.
    Insect biochemistry and molecular biology 05/2012; 42(9):603-9. · 3.25 Impact Factor
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    ABSTRACT: The discontinuous gas exchange cycle (DGC) is a breathing pattern displayed by many insects, characterized by periodic breath-holding and intermittently low tracheal O(2) levels. It has been hypothesized that the adaptive value of DGCs is to reduce oxidative damage, with low tracheal O(2) partial pressures (PO(2) ≈ 2-5 kPa) occurring to reduce the production of oxygen free radicals. If this is so, insects displaying DGCs should continue to actively defend a low tracheal PO(2) even when breathing higher than atmospheric levels of oxygen (hyperoxia). This behaviour has been observed in moth pupae exposed to ambient PO(2) up to 50 kPa. To test this observation in adult insects, we implanted fibre-optic oxygen optodes within the tracheal systems of adult migratory locusts Locusta migratoria exposed to normoxia, hypoxia and hyperoxia. In normoxic and hypoxic atmospheres, the minimum tracheal PO(2) that occurred during DGCs varied between 3.4 and 1.2 kPa. In hyperoxia up to 40.5 kPa, the minimum tracheal PO(2) achieved during a DGC exceeded 30 kPa, increasing with ambient levels. These results are consistent with a respiratory control mechanism that functions to satisfy O(2) requirements by maintaining PO(2) above a critical level, not defend against high levels of O(2).
    Biology letters 04/2012; 8(4):682-4. · 3.35 Impact Factor
  • Philip G D Matthews, Craig R White
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    ABSTRACT: Insects are at high risk of desiccation because of their small size, high surface-area-to-volume ratio, and air-filled tracheal system that ramifies throughout their bodies to transport O(2) and CO(2) to and from respiring cells. Although the tracheal system offers a high-conductance pathway for the movement of respiratory gases, it has the unintended consequence of allowing respiratory transpiration to the atmosphere. When resting, many species exchange respiratory gases discontinuously, and an early hypothesis for the origin of these discontinuous gas exchange cycles (DGCs) is that they serve to reduce respiratory water loss. In this study, we test this "hygric" hypothesis by comparing rates of CO(2) exchange and water loss among flower beetles Protaetia cretica (Cetoniinae, Scarabaeidae) breathing either continuously or discontinuously. We show that, consistent with the expectations of the hygric hypothesis, rates of total water loss are higher during continuous gas exchange than during discontinuous gas exchange and that the ratio of respiratory water loss to CO(2) exchange is lower during discontinuous gas exchange. This conclusion is in agreement with other studies of beetles and cockroaches that also support the hygric hypothesis. However, this result does not exclude other adaptive hypotheses supported by work on ants and moth pupae. This ambiguity may arise because there are multiple independent evolutionary origins of DGCs and no single adaptive function underlying their genesis. Alternatively, the observed reduction in water loss during DGCs may be a side effect of a nonadaptive gas exchange pattern that is elicited during periods of inactivity.
    Physiological and Biochemical Zoology 03/2012; 85(2):174-82. · 2.46 Impact Factor
  • Natalie G Schimpf, Philip G D Matthews, Craig R White
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    ABSTRACT: Metabolic rate and respiratory gas exchange patterns vary significantly both between and within species, even after a number of biotic and abiotic factors are taken into account. This suggests that such variation is of evolutionary importance, but the life history implications of this variation remain relatively poorly characterized. In the present study, we examine the effect of metabolic variation on starvation and desiccation resistance in the speckled cockroach Nauphoeta cinerea. We also compare the starvation and desiccation resistance of individuals that exchange respiratory gases continuously with those that breathe discontinuously. We show that metabolic rate has no effect on survival during food and water restriction, but cockroaches exhibiting discontinuous gas exchange cycles (DGCs) live longer than those that do not and those provisioned with water lived longer than those that were not. This finding represents the first demonstration that DGCs confer a fitness benefit, and supports the oldest hypothesis for the evolution of DGCs (which suggests that DGCs arose or are maintained to reduce respiratory water loss) as we also reveal reduced water loss (both respiratory and total) in cockroaches exhibiting discontinuous gas exchange.
    Evolution 02/2012; 66(2):597-604. · 4.86 Impact Factor
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    ABSTRACT: The reasons why metabolic rate (B) scales allometrically with body mass (M) remain hotly debated. The field is dominated by correlational analyses of the relationship between B and M; these struggle to disentangle competing explanations because both B and M are confounded with ontogeny, life history, and ecology. Here, we overcome these problems by using an experimental approach to test among competing metabolic theories. We examined the scaling of B in size-manipulated and intact colonies of a bryozoan and show that B scales with M(0.5). To explain this, we apply a general model based on the dynamic energy budget theory for metabolic organization that predicts B on the basis of energy allocation to assimilation, maintenance, growth, and maturation. Uniquely, this model predicts the absolute value of B, emphasizes that there is no single scaling exponent of B, and demonstrates that a single model can explain the variation in B seen in nature.
    The American Naturalist 12/2011; 178(6):746-54. · 4.55 Impact Factor
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    ABSTRACT: The hemimetabolous migratory locust Locusta migratoria progresses through five instars to the adult, increasing in size from 0.02 to 0.95 g, a 45-fold change. Hopping locomotion occurs at all life stages and is supported by aerobic metabolism and provision of oxygen through the tracheal system. This allometric study investigates the effect of body mass (Mb) on oxygen consumption rate (MO2, μmol h(-1)) to establish resting metabolic rate (MRO2), maximum metabolic rate during hopping (MMO2) and maximum metabolic rate of the hopping muscles (MMO2,hop) in first instar, third instar, fifth instar and adult locusts. Oxygen consumption rates increased throughout development according to the allometric equations MRO2=30.1Mb(0.83±0.02), MMO2=155Mb(1.01±0.02), MMO2,hop=120Mb(1.07±0.02) and, if adults are excluded, MMO2,juv=136Mb(0.97±0.02) and MMO2,juv,hop=103Mb(1.02±0.02). Increasing body mass by 20-45% with attached weights did not increase mass-specific MMO2 significantly at any life stage, although mean mass-specific hopping MO2 was slightly higher (ca. 8%) when juvenile data were pooled. The allometric exponents for all measures of metabolic rate are much greater than 0.75, and therefore do not support West, Brown and Enquist’s optimised fractal network model, which predicts that metabolism scales with a 3⁄4-power exponent owing to limitations in the rate at which resources can be transported within the body.
    Journal of Experimental Biology 10/2011; 214(Pt 19):3218-24. · 3.24 Impact Factor
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    ABSTRACT: Taylor and Weibel's theory of symmorphosis predicts that structures of the respiratory system are matched to maximum functional requirements with minimal excess capacity. We tested this hypothesis in the respiratory system of the migratory locust, Locusta migratoria, by comparing the aerobic capacity of the jumping muscles with the morphology of the oxygen cascade in the hopping legs using an intraspecific allometric analysis of different body mass (M(b)) at selected juvenile life stages. The maximum oxygen consumption rate of the hopping muscle during jumping exercise scales as M(b)(1.02±0.02), which parallels the scaling of mitochondrial volume in the hopping muscle, M(b)(1.02±0.08), and the total surface area of inner mitochondrial membrane, M(b)(0.99±0.10). Likewise, at the oxygen supply end of the insect respiratory system, there is congruence between the aerobic capacity of the hopping muscle and the total volume of tracheoles in the hopping muscle, M(b)(0.99±0.16), the total inner surface area of the tracheoles, M(b)(0.99±0.16), and the anatomical radial diffusing capacity of the tracheoles, M(b)(0.99±0.18). Therefore, the principles of symmorphosis are upheld at each step of the oxygen cascade in the respiratory system of the migratory locust.
    Journal of Experimental Biology 10/2011; 214(Pt 19):3225-37. · 3.24 Impact Factor
  • Philip G D Matthews, Roger S Seymour
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    ABSTRACT: Aquatic backswimmers (Anisops spp.) collect oxygen from the atmosphere in order to breathe underwater, carrying it within a bubble of air on the ventral surface of their body and bound within haemoglobin-filled cells inside their abdomen. These oxygen stores are interconnected via the abdominal spiracles and the tracheal system. Fibre optic oxygen probes were used to measure PO(2) changes within the air bubbles of submerged backswimmers (Anisops deanei) and these measurements were transformed into in vivo haemoglobin-oxygen equilibrium curves (OECs) using a biotonometric approach. The haemoglobin displayed a triphasic, highly sigmoid OEC with a P(50) of 3.90 kPa. Comparisons made with a previous in vitro analysis of Anisops haemoglobin demonstrate that while the apparent cooperativity and oxygen affinity are considerably higher in vivo, both measurements share unusual Hb-O(2) binding characteristics. The affinity and cooperativity of the backswimmers' haemoglobin appears adaptive as it lengthens dives and promotes neutral buoyancy. While there are limitations associated with biotonometry, the in vivo OEC accurately represents the loading and unloading of biologically available oxygen within the backswimmers' haemoglobin cells. Potential errors associated with determining the OEC are small, as evaluated with sensitivity analyses in numerical models.
    Journal of insect physiology 09/2011; 57(12):1698-706. · 2.24 Impact Factor
  • Philip G D Matthews, Craig R White
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    ABSTRACT: Ventilatory control of internal CO(2) plays an important role in regulating extracellular acid-base balance in terrestrial animals. While this phenomenon is well understood among vertebrates, the role that respiration plays in the acid-base balance of insects is in need of much further study. To measure changes in insect haemolymph pH, we implanted micro pH optodes into the haemocoel of cockroaches (Nauphoeta cinerea). They were then exposed to normoxic, hypoxic, hyperoxic and hypercapnic atmospheres while their haemolymph pH, VCO(2) and abdominal ventilation frequency were measured simultaneously. Intratracheal O(2) levels were also measured in separate experiments. It was found that cockroaches breathing continuously control their ventilation to defend a haemolymph pH of 7.3, except under conditions where hypoxia (<10% O(2)) induces hyperventilation, or where ambient hypercapnia is in excess of haemolymph (>1% CO(2)). In contrast, intratracheal O(2) levels fluctuated widely, but on average remained above 15% in normoxic (21% O(2)) atmospheres. Decapitation caused the cockroaches to display discontinuous gas exchange cycles (DGCs). The alternating periods of ventilation and apnoea during DGCs caused haemolymph pH to fluctuate by 0.11 units. Exposure to hypoxia caused haemolymph pH to increase and initiated brief bouts of spiracular opening prior to the active ventilation phase. The spontaneous occurrence of DGCs in decapitated cockroaches indicates that central pattern generators in the thoracic and abdominal ganglia generate the periodic gas exchange pattern in the absence of control from the cephalic ganglion. This pattern continues to maintain gas exchange, but with less precision.
    Journal of Experimental Biology 09/2011; 214(Pt 18):3062-73. · 3.24 Impact Factor
  • Philip G D Matthews, Craig R White
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    ABSTRACT: Some insects display an intermittent pattern of gas exchange while at rest, often going hours between breaths. These discontinuous gas exchange cycles (DGCs) are known to have evolved independently within five insect orders, but their possible adaptive benefit and evolutionary origin remain an enigma. Current research is primarily concerned with testing three adaptive hypotheses: that DGCs originally evolved or are currently maintained to (1) limit respiratory water loss, (2) enhance gas exchange in subterranean environments, or (3) limit oxidative damage. These adaptive explanations fail to unite a range of apparently contradictory observations regarding the insects that display DGCs and the conditions under which they occur. Here we argue that DGCs are explained by circadian, developmental, or artificially induced reductions in brain activity. We conclude that this pattern results from the thoracic and abdominal ganglia regulating ventilation in the absence of control from higher neural centers, and it is indicative of a sleeplike state.
    The American Naturalist 11/2010; 177(1):130-4. · 4.55 Impact Factor
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    ABSTRACT: The reasons why many insects breathe discontinuously at rest are poorly understood and hotly debated. Three adaptive hypotheses attempt to explain the significance of these discontinuous gas exchange cycles (DGCs), whether it be to save water, to facilitate gas exchange in underground environments or to limit oxidative damage. Comparative studies favour the water saving hypothesis and mechanistic studies are equivocal but no study has examined the acclimation responses of adult insects chronically exposed to a range of respiratory environments. The present research is the first manipulative study of such chronic exposure to take a strong-inference approach to evaluating the competing hypotheses according to the explicit predictions stemming from them. Adult cockroaches (Nauphoeta cinerea) were chronically exposed to various treatments of different respiratory gas compositions (O(2), CO(2) and humidity) and the DGC responses were interpreted in light of the a priori predictions stemming from the competing hypotheses. Rates of mass loss during respirometry were also measured for animals acclimated to a range of humidity conditions. The results refute the hypotheses of oxidative damage and underground gas exchange, and provide evidence supporting the hypothesis that DGCs serve to reduce respiratory water loss: cockroaches exposed to low humidity conditions exchange respiratory gases for shorter durations during each DGC and showed lower rates of body mass loss during respirometry than cockroaches exposed to high humidity conditions.
    Journal of Experimental Biology 10/2009; 212(17):2773-80. · 3.24 Impact Factor

Publication Stats

107 Citations
119.95 Total Impact Points

Institutions

  • 2009–2013
    • University of Queensland 
      • School of Biological Sciences
      Brisbane, Queensland, Australia
  • 2006–2013
    • University of Adelaide
      • • School of Earth and Environmental Sciences
      • • Discipline of Environmental Biology
      Adelaide, South Australia, Australia