scholarly journals Conspecific chemical cues drive density-dependent metabolic suppression independently of resource intake

2020 ◽  
Vol 223 (17) ◽  
pp. jeb224824
Author(s):  
Melanie K. Lovass ◽  
Dustin J. Marshall ◽  
Giulia Ghedini
Keyword(s):  
Metabolic Rate ◽  
Chemical Cues ◽  
Marine Invertebrates ◽  
Feeding Activity ◽  
Food Competition ◽  
Conspecific Density ◽  
Physiological Processes ◽  
Metabolic Suppression ◽  
Metabolic Variation ◽  
Metabolic Reduction

ABSTRACTWithin species, individuals of the same size can vary substantially in their metabolic rate. One source of variation in metabolism is conspecific density – individuals in denser populations may have lower metabolism than those in sparser populations. However, the mechanisms through which conspecifics drive metabolic suppression remain unclear. Although food competition is a potential driver, other density-mediated factors could act independently or in combination to drive metabolic suppression, but these drivers have rarely been investigated. We used sessile marine invertebrates to test how food availability interacts with oxygen availability, water flow and chemical cues to affect metabolism. We show that conspecific chemical cues induce metabolic suppression independently of food and this metabolic reduction is associated with the downregulation of physiological processes rather than feeding activity. Conspecific cues should be considered when predicting metabolic variation and competitive outcomes as they are an important, but underexplored, source of variation in metabolic traits.

scholarly journals Predator chemical cues decrease attack time and increase metabolic rate in an orb-web spider

2019 ◽  
Vol 222 (22) ◽  
pp. jeb212738 ◽  
Author(s):  
Mohammad Ameri ◽  
Darrell J. Kemp ◽  
Katherine L. Barry ◽  
Marie E. Herberstein
Keyword(s):  
Metabolic Rate ◽  
Chemical Cues ◽  
Web Spider ◽  
Orb Web ◽  
Attack Time

Predator chemical cues affect prey feeding activity differently in juveniles and adults

2012 ◽  
Vol 90 (1) ◽  
pp. 128-132 ◽  
Author(s):  
Bradley R. Johnston ◽  
Markus Molis ◽  
Ricardo A. Scrosati
Keyword(s):  
Life History ◽  
Chemical Cues ◽  
Prey Species ◽  
Feeding Activity ◽  
Life History Stage ◽  
Ontogenetic Changes ◽  
Nucella Lapillus ◽  
Nonconsumptive Effects ◽  
Predator Cues ◽  
Predator Effects

Nonconsumptive predator effects on prey behaviour are common in nature, but the possible influence of prey life-history stage on such responses is poorly known. We investigated whether prey life-history stage may be a factor affecting prey feeding activity responses to predator chemical cues, for which we used dogwhelks ( Nucella lapillus (L., 1758)) and their main prey, barnacles ( Semibalanus balanoides (L., 1758)), as a model system. Barnacles use their modified legs (cirri) to filter food from the water column. Through a manipulative laboratory experiment, we tested the hypothesis that the presence of dogwhelks affects the frequency of leg swipes differently in juvenile and adult barnacles. Juveniles showed a similar feeding activity with and without nearby dogwhelks, but adults exhibited a significantly lower frequency of leg swipes when dogwhelks were present. Such an ontogenetic change in the response of barnacles to predatory cues might have evolved as a result of dogwhelks preferring adult barnacles over juvenile barnacles, as found previously. Alternatively, barnacles could learn to recognize predator cues as they age, as shown for other prey species. Overall, our study indicates that the nonconsumptive effects of predators on prey need to be fully understood under consideration of the possible ontogenetic changes in prey responses to predator cues.

The Relation between Cerebral Metabolic Rate and Ischemic Depolarization 

1995 ◽  
Vol 82 (5) ◽  
pp. 1199-1208 ◽  
Author(s):  
Ken Nakashima ◽  
Michael M. Todd ◽  
David S. Warner
Keyword(s):  
Metabolic Rate ◽  
High Dose ◽  
Energy Depletion ◽  
Cerebral Metabolic Rate ◽  
Anesthetized Rats ◽  
Metabolic Suppression ◽  
Energy Stores ◽  
Ischemic Depolarization ◽  
The Times ◽  
Unique Mechanism

Background Reductions in cerebral metabolic rate may increase the brain's tolerance of ischemia. However, outcome studies suggest that reductions in cerebral metabolic rate produced by anesthetics and by hypothermia may not be equally efficacious. To examine this question, we measured the effects of hypothermia, pentobarbital, and isoflurane on the cerebral metabolic rate for glucose (CMRG) and on the time to the loss of normal membrane ion gradients (terminal ischemic depolarization) of the cortex during complete global ischemia. Methods As pericranial temperature was varied between 39 and 25 degrees C in normocapnic halothane-anesthetized rats, CMRG (using 14C-deoxyglucose) or the time to depolarization (using a glass microelectrode in the cortex) after a K(+)-induced cardiac arrest was measured. In other studies, CMRG and depolarization times were measured in normothermic animals (37.7 +/- 0.2 degrees C) anesthetized with high-dose pentobarbital or isoflurane (both producing burst suppression on the electroencephalogram) or in halothane-anesthetized animals whose temperatures were reduced to 27.4 +/- 0.3 degrees C. These three states were designed to produce equivalent CMRG values. Results As temperature was reduced from 39 to 25 degrees C, CMRG decreased from 66 to 21 microM.100 g-1.min-1 (Q10 = 2.30), and depolarization times increased from 76 to 326 s. In similarly anesthetized animals at approximately 27 degrees C, CMRG was 32 +/- 4 microM.100 g-1.min-1 (mean +/- SD), whereas in normothermic pentobarbital- and isoflurane-anesthetized rats, CMRG values were 33 +/- 3 and 37 +/- 4 microM.100 g-1.min-1, respectively (P = 0.072 by one-way analysis of variance). Despite these similar metabolic rates, the times to depolarization were markedly different: for hypothermia it was 253 +/- 29 s, for pentobarbital 109 +/- 24 s, and for isoflurane 130 +/- 28 s (P < 0.0001). Conclusions The time to terminal depolarization is believed to be a measure of the rate at which energy stores are depleted. In this study there was a strong correlation between hypothermic reductions in CMRG and increases in the time to depolarization. This finding supports the belief that metabolic suppression may offer some cerebral protection. However, equivalent reductions in CMRG produced by hypothermia and by anesthesia were not equivalent in their effects on membrane failure. Whether hypothermia slows energy depletion by some unique mechanism or directly retards depolarization is unknown.

scholarly journals Effects of Diaphorina citri Population Density on Daily Timing of Vibrational Communication Calls: Potential Benefits in Finding Forage

Insects ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 182
Author(s):  
Richard W. Mankin ◽  
Rikin Patel ◽  
Mason Grugnale ◽  
Ethan Jetter
Keyword(s):  
Population Density ◽  
Chemical Cues ◽  
Reproductive Fitness ◽  
High Density ◽  
Vibrational Communication ◽  
Low Density ◽  
Diaphorina Citri ◽  
Conspecific Density ◽  
Potential Benefits ◽  
Communication Calls

Adult Diaphorina citri (ACP) use visual and chemical cues to locate young citrus flush shoots on which they forage and oviposit, and they use vibrational communication duetting calls as cues to help locate mates. For individual pairs, calling and mating usually peaks between 10:00 and 15:00. To explore whether call rates (calls/h) are affected by interactions with nearby conspecifics, rates were compared in small citrus trees on which either 5 or 25 ACP female and male pairs had been released at 17:00 for later recording from sunrise (06:00) to 22:00. Final ACP locations were noted 40 h after release. Call rates were similar in both treatments during normal mating hours. However, rates were significantly higher for low- than high-density treatments between 06:00 and 10:00, which suggests calling during this period may be affected by conspecific density. Both sexes aggregated on flush at both densities. We discuss the potential that ACP producing calls near sunrise, outside of normal mating hours, might benefit from gains in reproductive fitness in low-density contexts if they call not only to locate mates but also to locate preferred flush—in which case, co-opting of vibrations to disrupt both mating and foraging may be feasible.

Politics for the Polyps

2016 ◽  
Vol 71 (1) ◽  
pp. 64-88 ◽  
Author(s):  
Daniel Harris
Keyword(s):  
Working Class ◽  
Personal Identity ◽  
Political Development ◽  
Marine Invertebrates ◽  
Physiological Processes ◽  
Peculiar Form ◽  
Economic Practices ◽  
Colonial Organisms

Daniel Harris, “Politics for the Polyps: The Compound Organism as a ‘Peculiar Form of Communism’ in Charles Kingsley’s Alton Locke and The Water-Babies” (pp. 64–88) Charles Kingsley’s novels and political writings are saturated with references to physiological processes in marine invertebrates. In particular, the forms of his novels take their inspiration from functional arrangements in colonial organisms such as corals, in which “individual” polyps are physiologically linked to their neighbors. Alton Locke (1851) and The Water-Babies (1863) attempt to explain the benefits of cooperative economic practices (e.g., the associative workshop) and the dangers of cooperative political practices (e.g., the Chartist mass meeting) by jettisoning British Enlightenment assumptions about personal identity. Instead, Kingsley’s novels use discontinuous and communal physiological processes in invertebrates, such as corals and jellyfish, as frameworks for representing psychological and political development. Ultimately, Kingsley seeks to intervene in mid-century debates about how to individuate members of the working class by suggesting that reformist measures must be grounded in a physiological understanding of individuation that contravenes psychological definitions of individuality.

scholarly journals Triiodothyronine (T3) levels fluctuate in response to ambient temperature rather than nutritional status in a wild tropical ungulate

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
L Hunninck ◽  
C R Jackson ◽  
R May ◽  
E Røskaft ◽  
R Palme ◽  
...  
Keyword(s):  
Nutritional Status ◽  
Metabolic Rate ◽  
Ambient Temperature ◽  
Food Quality ◽  
Human Disturbance ◽  
Physiological Stress ◽  
Food Competition ◽  
Physiological Status ◽  
Human Disturbances ◽  
Poor Nutritional Status

Abstract Animals can employ a range of physiological mechanisms in response to unpredictable changes within their environment, such as changes in food availability and human disturbances. For example, impala exhibit higher faecal glucocorticoid metabolite (FGM) levels—indicative of physiological stress—in response to low food quality and higher human disturbance. In this study, we measured faecal triiodothyronine (T3) metabolite (FTM) levels in 446 wild impala from 2016 to 2018 to test the hypothesis that environmental and human disturbances would affect their physiological status. We also validated a faecal thyroid hormone assay. T3 levels mainly regulate metabolic rate and drive thermoregulation—increasing with colder temperatures. We predicted that individuals would have lower FTM levels, indicative of poor physiological status, (i) when food quality was poor, (ii) when ambient temperature (Ta) was high, (iii) in areas of high human disturbance (due to food competition with livestock) and (iv) when FGM levels were high. Interestingly, we found that Ta was the most important predictor of FTM—FTM levels decreased by 70% from lowest to highest Ta—and food quality and human disturbance only influenced FTM levels when Ta was accounted for. FTM levels also tended to increase with increasing FGM levels, opposite our predictions. Our results suggest that food quality and availability may only partially influence FTM levels and that fluctuations in Ta are a significant driver of FTM levels in a wild tropical ungulate. Given that thyroid hormones are primarily responsible for regulating metabolic rate, they may be better indicators of how wild animals metabolically and energetically respond to environmental factors and only indicate poor nutritional status in extreme cases.

scholarly journals Short-term captivity influences maximal cold-induced metabolic rates and their repeatability in summer-acclimatized American goldfinches Spinus tristis

2013 ◽  
Vol 59 (4) ◽  
pp. 439-448 ◽  
Author(s):  
David L. Swanson ◽  
Marisa O. King
Keyword(s):  
Body Composition ◽  
Metabolic Rate ◽  
Muscle Growth ◽  
Metabolic Responses ◽  
Phenotypic Flexibility ◽  
Metabolic Rates ◽  
Wild Populations ◽  
Short Term ◽  
Fitness Consequences ◽  
Metabolic Variation

Abstract Studies of metabolic variation in birds have involved both wild and captive individuals, but few studies have investigated whether captivity directly influences metabolic rates, despite such variation potentially confounding conclusions regarding how metabolic rates respond to the conditions under study. In addition, whether short-term captivity influences metabolic rate repeatability in birds is currently uninvestigated. In this study, we measured Msum (maximal cold-induced metabolic rates) in summer acclimatized American goldfinches Spinus tristis directly after capture from wild populations, after approximately 2 weeks of indoor captivity (Captive 1), and again after an additional 1–2 weeks of captivity (Captive 2). Msum increased significantly (16.9%) following the initial captive period, but remained stable thereafter. Body mass (Mb) also increased significantly (9.2%) during the initial captive period but remained stable thereafter, suggesting that muscle growth and/or remodeling of body composition produced the observed metabolic variation. Mb and Msum were not significantly repeatable between wild and Captive 1 birds, but were significantly repeatable between Captive 1 and Captive 2 groups. These data suggest that caution must be exercised when extrapolating metabolic rates from short-term captive to wild populations. In addition, Msum was a repeatable trait for birds under conditions where mean metabolic rates remained stable, but Msum repeatability disappeared during acclimation to conditions promoting phenotypically flexible metabolic responses. This suggests that the capacity for phenotypic flexibility varies among individuals, and such variation could have fitness consequences.

Design and Evaluation of a Proportional Myoelectric Controller for Hip Exoskeletons During Walking

2018 ◽  
Author(s):  
Hsiang Hsu ◽  
Inseung Kang ◽  
Aaron J. Young
Keyword(s):  
Metabolic Rate ◽  
Sagittal Plane ◽  
Metabolic Cost ◽  
Emg Activity ◽  
Neural Controller ◽  
Output Torque ◽  
Gait Phase ◽  
High Level ◽  
Series Elastic Actuators ◽  
Metabolic Reduction

The purpose of this study was to explore the effectiveness of a neural controller for a single-joint bilateral hip exoskeleton. The device provides mechanical torque in the sagittal plane and uses series elastic actuators for feedback control. The system consists of three control layers: (1) a high-level controller that estimates the current gait phase, (2) a mid-level controller that converts the electromyography (EMG) signals to desired exoskeleton torques, and (3) a low-level controller that ensures the output torque matches the commanded torque. To evaluate the effectiveness of the proportional EMG controller, one able-body subject walked with the exoskeleton under 3 assistance conditions: (1) a baseline proportional gain condition (× G), (2) a double proportional gain condition (× 2G) for faster scaling, and (3) an on/off set value torque assistance (SV). The third condition provides the same net mechanical power as the baseline (× G) condition to compare whether proportional scaling of the hip torque was significant. The subject’s hip-joint kinematics, metabolic rate, and muscle activities were collected as outcome measurements. In summary, the EMG controller could generate seamless torque to the user with a response time of 80 ms. The × 2G condition resulted in a 23.3% EMG activity reduction while SV condition reduced the metabolic rate by 8.1%. Interestingly, the largest EMG reduction condition (× 2G) did not result in largest metabolic reduction (SV). Our preliminary findings suggest that the proportional scaling of the hip torque may not be the most important parameter to minimize metabolic cost.

scholarly journals Low global sensitivity of metabolic rate to temperature in calcified marine invertebrates

Oecologia ◽  
2013 ◽  
Vol 174 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Sue-Ann Watson ◽  
Simon A. Morley ◽  
Amanda E. Bates ◽  
Melody S. Clark ◽  
Robert W. Day ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Marine Invertebrates ◽  
Global Sensitivity

scholarly journals Sulfide metabolism and the mechanism of torpor

2021 ◽  
Vol 224 (17) ◽  
Author(s):  
Birgitte S. Jensen ◽  
Angela Fago
Keyword(s):  
Body Temperature ◽  
Metabolic Rate ◽  
Mitochondrial Respiration ◽  
Mammalian Species ◽  
Winter Season ◽  
Cold Winter ◽  
Sulfide:Quinone Oxidoreductase ◽  
Metabolic Suppression

ABSTRACT Hibernation is a powerful response of a number of mammalian species to reduce energy during the cold winter season, when food is scarce. Mammalian hibernators survive winter by spending most of the time in a state of torpor, where basal metabolic rate is strongly suppressed and body temperature comes closer to ambient temperature. These torpor bouts are regularly interrupted by short arousals, where metabolic rate and body temperature spontaneously return to normal levels. The mechanisms underlying these changes, and in particular the strong metabolic suppression of torpor, have long remained elusive. As summarized in this Commentary, increasing evidence points to a potential key role for hydrogen sulfide (H2S) in the suppression of mitochondrial respiration during torpor. The idea that H2S could be involved in hibernation originated in some early studies, where exogenous H2S gas was found to induce a torpor-like state in mice, and despite some controversy, the idea persisted. H2S is a widespread signaling molecule capable of inhibiting mitochondrial respiration in vitro and studies found significant in vivo changes in endogenous H2S metabolites associated with hibernation or torpor. Along with increased expression of H2S-synthesizing enzymes during torpor, H2S degradation catalyzed by the mitochondrial sulfide:quinone oxidoreductase (SQR) appears to have a key role in controlling H2S availability for inhibiting respiration. Specifically, in thirteen-lined squirrels, SQR is highly expressed and inhibited in torpor, possibly by acetylation, thereby limiting H2S oxidation and causing inhibition of respiration. H2S may also control other aspects associated with hibernation, such as synthesis of antioxidant enzymes and of SQR itself.

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