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Andersen MK, Willot Q, MacMillan HA. A neurophysiological limit and its biogeographic correlations: cold-induced spreading depolarization in tropical butterflies. J Exp Biol 2023; 226:jeb246313. [PMID: 37665251 DOI: 10.1242/jeb.246313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 08/23/2023] [Indexed: 09/05/2023]
Abstract
The physiology of insects is directly influenced by environmental temperature, and thermal tolerance is therefore intrinsically linked to their thermal niche and distribution. Understanding the mechanisms that limit insect thermal tolerance is crucial to predicting biogeography and range shifts. Recent studies on locusts and flies suggest that the critical thermal minimum (CTmin) follows a loss of CNS function via a spreading depolarization. We hypothesized that other insect taxa share this phenomenon. Here, we investigate whether spreading depolarization events occur in butterflies exposed to cold. Supporting our hypothesis, we found that exposure to stressful cold induced spreading depolarization in all 12 species tested. This reinforces the idea that spreading depolarization is a common mechanism underlying the insect CTmin. Furthermore, our results highlight how CNS function is tuned to match the environment of a species. Further research into the physiology underlying spreading depolarization will likely elucidate key mechanisms determining insect thermal tolerance and ecology.
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Affiliation(s)
| | - Quentin Willot
- Department of Biology, Aarhus University, Aarhus 8000, Denmark
| | - Heath A MacMillan
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
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2
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Andersen MK, Robertson RM, MacMillan HA. Plasticity in Na+/K+-ATPase thermal kinetics drives variation in the temperature of cold-induced neural shutdown of adult Drosophila melanogaster. J Exp Biol 2022; 225:285893. [PMID: 36477887 DOI: 10.1242/jeb.244923] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/29/2022] [Indexed: 12/13/2022]
Abstract
Most insects can acclimate to changes in their thermal environment and counteract temperature effects on neuromuscular function. At the critical thermal minimum, a spreading depolarization (SD) event silences central neurons, but the temperature at which this event occurs can be altered through acclimation. SD is triggered by an inability to maintain ion homeostasis in the extracellular space in the brain and is characterized by a rapid surge in extracellular K+ concentration, implicating ion pump and channel function. Here, we focused on the role of the Na+/K+-ATPase specifically in lowering the SD temperature in cold-acclimated Drosophila melanogaster. After first confirming cold acclimation altered SD onset, we investigated the dependency of the SD event on Na+/K+-ATPase activity by injecting the inhibitor ouabain into the head of the flies to induce SD over a range of temperatures. Latency to SD followed the pattern of a thermal performance curve, but cold acclimation resulted in a left-shift of the curve to an extent similar to its effect on the SD temperature. With Na+/K+-ATPase activity assays and immunoblots, we found that cold-acclimated flies have ion pumps that are less sensitive to temperature, but do not differ in their overall abundance in the brain. Combined, these findings suggest a key role for plasticity in Na+/K+-ATPase thermal sensitivity in maintaining central nervous system function in the cold, and more broadly highlight that a single ion pump can be an important determinant of whether insects can respond to their environment to remain active at low temperatures.
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Affiliation(s)
| | | | - Heath A MacMillan
- Department of Biology, Carleton University, Ottawa, ON, Canada, K1S 5B6
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3
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Brain dysfunction during warming is linked to oxygen limitation in larval zebrafish. Proc Natl Acad Sci U S A 2022; 119:e2207052119. [PMID: 36122217 PMCID: PMC9522358 DOI: 10.1073/pnas.2207052119] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding the physiological mechanisms that limit animal thermal tolerance is crucial in predicting how animals will respond to increasingly severe heat waves. Despite their importance for understanding climate change impacts, these mechanisms underlying the upper thermal tolerance limits of animals are largely unknown. It has been hypothesized that the upper thermal tolerance in fish is limited by the thermal tolerance of the brain and is ultimately caused by a global brain depolarization. In this study, we developed methods for measuring the upper thermal limit (CTmax) in larval zebrafish (Danio rerio) with simultaneous recordings of brain activity using GCaMP6s calcium imaging in both free-swimming and agar-embedded fish. We discovered that during warming, CTmax precedes, and is therefore not caused by, a global brain depolarization. Instead, the CTmax coincides with a decline in spontaneous neural activity and a loss of neural response to visual stimuli. By manipulating water oxygen levels both up and down, we found that oxygen availability during heating affects locomotor-related neural activity, the neural response to visual stimuli, and CTmax. Our results suggest that the mechanism limiting the upper thermal tolerance in zebrafish larvae is insufficient oxygen availability causing impaired brain function.
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4
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Robertson RM, Moyes CD. Rapid cold hardening increases axonal Na+/K+-ATPase activity and enhances performance of a visual motion detection circuit in Locusta migratoria. J Exp Biol 2022; 225:275626. [DOI: 10.1242/jeb.244097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 04/28/2022] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Rapid cold hardening (RCH) is a type of phenotypic plasticity that delays the occurrence of chill coma in insects. Chill coma is mediated by a spreading depolarization of neurons and glia in the CNS, triggered by a failure of ion homeostasis. We used biochemical and electrophysiological approaches in the locust, Locusta migratoria, to test the hypothesis that the protection afforded by RCH is mediated by activation of the Na+/K+-ATPase (NKA) in neural tissue. RCH did not affect NKA activity measured in a biochemical assay of homogenized thoracic ganglia. However, RCH hyperpolarized the axon of a visual interneuron (DCMD) and increased the amplitude of an activity-dependent hyperpolarization (ADH) shown previously to be blocked by ouabain. RCH also improved performance of the visual circuitry presynaptic to DCMD to minimize habituation and increase excitability. We conclude that RCH enhances in situ NKA activity in the nervous system but also affects other neuronal properties that promote visual processing in locusts.
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Affiliation(s)
- R. Meldrum Robertson
- Queen's University Department of Biology, 3118 Biosciences Complex , , Kingston, ON , Canada , K7L 3N6
| | - Christopher D. Moyes
- Queen's University Department of Biology, 3118 Biosciences Complex , , Kingston, ON , Canada , K7L 3N6
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5
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O'Neill E, Davis HE, MacMillan HA. A lack of repeatability creates the illusion of a trade-off between basal and plastic cold tolerance. Proc Biol Sci 2021; 288:20212121. [PMID: 34875191 PMCID: PMC8651406 DOI: 10.1098/rspb.2021.2121] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/17/2021] [Indexed: 01/10/2023] Open
Abstract
The thermotolerance-plasticity trade-off hypothesis predicts that ectotherms with greater basal thermal tolerance have a lower acclimation capacity. This hypothesis has been tested at both high and low temperatures but the results often conflict. If basal tolerance constrains plasticity (e.g. through shared mechanisms that create physiological constraints), it should be evident at the level of the individual, provided the trait measured is repeatable. Here, we used chill-coma onset temperature and chill-coma recovery time (CCO and CCRT; non-lethal thermal limits) to quantify cold tolerance of Drosophila melanogaster across two trials (pre- and post-acclimation). Cold acclimation improved cold tolerance, as expected, but individual measurements of CCO and CCRT in non-acclimated flies were not (or only slightly) repeatable. Surprisingly, however, there was still a strong correlation between basal tolerance and plasticity in cold-acclimated flies. We argue that this relationship is a statistical artefact (specifically, a manifestation of regression to the mean; RTM) and does not reflect a true trade-off or physiological constraint. Thermal tolerance trade-off patterns in previous studies that used similar methodology are thus likely to be impacted by RTM. Moving forward, controlling and/or correcting for RTM effects is critical to determining whether such a trade-off or physiological constraint exists.
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Affiliation(s)
- Erica O'Neill
- Department of Biology, Carleton University, ON K1S 5B6, Canada
| | - Hannah E. Davis
- Department of Biology, Carleton University, ON K1S 5B6, Canada
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6
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Chipchase KM, Enders AM, Jacobs EG, Hughes MR, Killian KA. Effect of a single cold stress exposure on the reproductive behavior of male crickets. JOURNAL OF INSECT PHYSIOLOGY 2021; 133:104287. [PMID: 34302838 DOI: 10.1016/j.jinsphys.2021.104287] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 06/17/2021] [Accepted: 07/15/2021] [Indexed: 06/13/2023]
Abstract
Cold stress is an important abiotic factor that can impact insect physiology, behavior, and overall fitness. Upon exposure to cold temperature, many insects enter a reversible state of immobility called chill coma. If the cold stress is brief and mild enough, insects can recover and regain full mobility upon return to warmer temperatures. However, the long-term impact of sublethal cold stress on insect behavior has been understudied. Here, sexually naïve adult male Acheta domesticus crickets were exposed to a single 0 °C cold stress for 6 h. One week later, the ability of these males to mate with a female was examined. For mating trials, a cold stressed male cricket was paired with a non-cold stressed, control female. Control pairs were comprised of a non-cold stressed control male and control female. Cold exposed males were less successful at mating than control males because most did not carry a spermatophore at the time of their mating trials. However, when these cold stressed males were allowed 1 h of chemosensory contact with a female, most produced a spermatophore. Males that produced spermatophores were given the opportunity to mate once with a female, and stressed males that successfully mated sired as many offspring as did control males. However, our results support that a single cold stress exposure can negatively impact the reproductive fitness of male crickets since it reduced their capacity to carry spermatophores and, as a consequence, to attract females.
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Affiliation(s)
- Kathryn M Chipchase
- Department of Biology, 258 Pearson Hall, Miami University, Oxford, OH 45056, USA
| | - Alexa M Enders
- Department of Biology, 258 Pearson Hall, Miami University, Oxford, OH 45056, USA
| | - Elizabeth G Jacobs
- Department of Biology, 258 Pearson Hall, Miami University, Oxford, OH 45056, USA
| | - Michael R Hughes
- Department of Biology, 258 Pearson Hall, Miami University, Oxford, OH 45056, USA
| | - Kathleen A Killian
- Department of Biology, 258 Pearson Hall, Miami University, Oxford, OH 45056, USA.
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7
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Himmel NJ, Letcher JM, Sakurai A, Gray TR, Benson MN, Donaldson KJ, Cox DN. Identification of a neural basis for cold acclimation in Drosophila larvae. iScience 2021; 24:102657. [PMID: 34151240 PMCID: PMC8192725 DOI: 10.1016/j.isci.2021.102657] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 04/05/2021] [Accepted: 05/25/2021] [Indexed: 11/29/2022] Open
Abstract
Low temperatures can be fatal to insects, but many species have evolved the ability to cold acclimate, thereby increasing their cold tolerance. It has been previously shown that Drosophila melanogaster larvae perform cold-evoked behaviors under the control of noxious cold-sensing neurons (nociceptors), but it is unknown how the nervous system might participate in cold tolerance. Herein, we describe cold-nociceptive behavior among 11 drosophilid species; we find that the predominant cold-evoked larval response is a head-to-tail contraction behavior, which is likely inherited from a common ancestor, but is unlikely to be protective. We therefore tested the hypothesis that cold nociception functions to protect larvae by triggering cold acclimation. We found that Drosophila melanogaster Class III nociceptors are sensitized by and critical to cold acclimation and that cold acclimation can be optogenetically evoked, sans cold. Collectively, these findings demonstrate that cold nociception constitutes a peripheral neural basis for Drosophila larval cold acclimation.
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Affiliation(s)
- Nathaniel J Himmel
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Jamin M Letcher
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Akira Sakurai
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Thomas R Gray
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA.,Department of Biology, Brandeis University, Waltham, MA 02453, USA
| | - Maggie N Benson
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Kevin J Donaldson
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
| | - Daniel N Cox
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, USA
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8
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Harms NE, Knight IA, Pratt PD, Reddy AM, Mukherjee A, Gong P, Coetzee J, Raghu S, Diaz R. Climate Mismatch between Introduced Biological Control Agents and Their Invasive Host Plants: Improving Biological Control of Tropical Weeds in Temperate Regions. INSECTS 2021; 12:insects12060549. [PMID: 34204761 PMCID: PMC8231509 DOI: 10.3390/insects12060549] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/20/2021] [Accepted: 06/07/2021] [Indexed: 12/15/2022]
Abstract
Simple Summary Mismatched distributions between biological control agents and their host plants occur for a variety of reasons but are often linked to climate, specifically differences in their low-temperature tolerances. How to measure and use low-temperature tolerances of control agents to inform agent prioritization, selection for redistribution, or predict efficacy is vitally important, but has not been previously synthesized in a single source. We discuss causes of climate mismatches between agents and target weeds, the traditional and non-traditional approaches that could be used to decrease the degree of mismatch and improve control, and regulatory issues to consider when taking such approaches. We also discuss the variety of cold tolerance metrics, their measurement and ecological value, and the types of modeling that can be carried out to improve predictions about potential distributions of agents. We also briefly touch on molecular bases for cold tolerance and opportunities for improving cold tolerance of agents using modern molecular tools. Abstract Many weed biological control programs suffer from large-scale spatial variation in success due to restricted distributions or abundances of agents in temperate climates. For some of the world’s worst aquatic weeds, agents are established but overwintering conditions limit their survival in higher latitudes or elevations. The resulting need is for new or improved site- or region-specific biological control tools. Here, we review this challenge with a focus on low-temperature limitations of agents and propose a roadmap for improving success. Investigations across spatial scales, from global (e.g., foreign exploration), to local (selective breeding), to individual organisms (molecular modification), are discussed. A combination of traditional (foreign) and non-traditional (introduced range) exploration may lead to the discovery and development of better-adapted agent genotypes. A multivariate approach using ecologically relevant metrics to quantify and compare cold tolerance among agent populations is likely required. These data can be used to inform environmental niche modeling combined with mechanistic modeling of species’ fundamental climate niches and life histories to predict where, when, and at what abundance agents will occur. Finally, synthetic and systems biology approaches in conjunction with advanced modern genomics, gene silencing and gene editing technologies may be used to identify and alter the expression of genes enhancing cold tolerance, but this technology in the context of weed biological control has not been fully explored.
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Affiliation(s)
- Nathan E. Harms
- Aquatic Ecology and Invasive Species Branch, Environmental Laboratory, US Army Engineer Research and Development Center, Vicksburg, MS 39180, USA;
- Correspondence: ; Tel.: +01-601-634-2976
| | - Ian A. Knight
- Aquatic Ecology and Invasive Species Branch, Environmental Laboratory, US Army Engineer Research and Development Center, Vicksburg, MS 39180, USA;
| | - Paul D. Pratt
- Invasive Species and Pollinator Health Research Unit, United States Department of Agriculture, Agricultural Research Service, Albany, CA 94710, USA; (P.D.P.); (A.M.R.)
| | - Angelica M. Reddy
- Invasive Species and Pollinator Health Research Unit, United States Department of Agriculture, Agricultural Research Service, Albany, CA 94710, USA; (P.D.P.); (A.M.R.)
| | | | - Ping Gong
- Environmental Processes Branch, Environmental Laboratory, US Army Engineer Research and Development Center, Vicksburg, MS 39180, USA;
| | - Julie Coetzee
- Centre for Biological Control, Botany Department, Rhodes University, Grahamstown 6140, South Africa;
| | - S. Raghu
- CSIRO Health & Biosecurity, Brisbane 4001, Australia;
| | - Rodrigo Diaz
- Department of Entomology, Louisiana State University, Baton Rouge, LA 70803, USA;
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9
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Cheslock A, Andersen MK, MacMillan HA. Thermal acclimation alters Na +/K +-ATPase activity in a tissue-specific manner in Drosophila melanogaster. Comp Biochem Physiol A Mol Integr Physiol 2021; 256:110934. [PMID: 33684554 DOI: 10.1016/j.cbpa.2021.110934] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 02/26/2021] [Accepted: 03/01/2021] [Indexed: 10/22/2022]
Abstract
Insects, like the model species Drosophila melanogaster, lose neuromuscular function and enter a state of paralysis (chill coma) at a population- and species-specific low temperature threshold that is decreased by cold acclimation. Entry into this coma is related to a spreading depolarization in the central nervous system, while recovery involves restoration of electrochemical gradients across muscle cell membranes. The Na+/K+-ATPase helps maintain ion balance and membrane potential in both the brain and hemolymph (surrounding muscles), and changes in thermal tolerance traits have therefore been hypothesized to be closely linked to variation in the expression and/or activity of this pump in multiple tissues. Here, we tested this hypothesis by measuring activity and thermal sensitivity of the Na+/K+-ATPase at the tagma-specific level (head, thorax and abdomen) in warm- (25 °C) and cold-acclimated (15 °C) flies by measuring Na+/K+-ATPase activity at 15, 20, and 25 °C. We relate differences in pump activity to differences in chill coma temperature, spreading depolarization temperature, and thermal dependence of muscle cell polarization. Differences in pump activity and thermal sensitivity induced by cold acclimation varied in a tissue-specific manner: While thermal sensitivity remained unchanged, cold-acclimated flies had decreased Na+/K+-ATPase activity in the thorax (mainly muscle) and head (mainly composed of brain). We argue that these changes may assist in maintenance of K+ homeostasis and membrane potential across muscle membranes, and discuss how reduced Na+/K+-ATPase activity in the brain may counterintuitively help insects delay coma onset in the cold.
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10
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Carrington J, Andersen MK, Brzezinski K, MacMillan HA. Hyperkalaemia, not apoptosis, accurately predicts insect chilling injury. Proc Biol Sci 2020; 287:20201663. [PMID: 33323084 DOI: 10.1098/rspb.2020.1663] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
There is a growing appreciation that insect distribution and abundance are associated with the limits of thermal tolerance, but the physiology underlying thermal tolerance remains poorly understood. Many insects, like the migratory locust (Locusta migratoria), suffer a loss of ion and water balance leading to hyperkalaemia (high extracellular [K+]) in the cold that indirectly causes cell death. Cells can die in several ways under stress, and how they die is of critical importance to identifying and understanding the nature of thermal adaptation. Whether apoptotic or necrotic cell death pathways are responsible for low-temperature injury is unclear. Here, we use a caspase-3 specific assay to indirectly quantify apoptotic cell death in three locust tissues (muscle, nerves and midgut) following prolonged chilling and recovery from an injury-inducing cold exposure. Furthermore, we obtain matching measurements of injury, extracellular [K+] and muscle caspase-3 activity in individual locusts to gain further insight into the mechanistic nature of chilling injury. We found a significant increase in muscle caspase-3 activity, but no such increase was observed in either nervous or gut tissue from the same animals, suggesting that chill injury primarily relates to muscle cell death. Levels of chilling injury measured at the whole animal level, however, were strongly correlated with the degree of haemolymph hyperkalaemia, and not apoptosis. These results support the notion that cold-induced ion balance disruption triggers cell death but also that apoptosis is not the main form of cell damage driving low-temperature injury.
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11
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Jørgensen LB, Robertson RM, Overgaard J. Neural dysfunction correlates with heat coma and CT max in Drosophila but does not set the boundaries for heat stress survival. J Exp Biol 2020; 223:jeb218750. [PMID: 32434804 DOI: 10.1242/jeb.218750] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 05/14/2020] [Indexed: 12/25/2022]
Abstract
When heated, insects lose coordinated movement followed by the onset of heat coma (critical thermal maximum, CTmax). These traits are popular measures to quantify interspecific and intraspecific differences in insect heat tolerance, and CTmax correlates well with current species distributions of insects, including Drosophila Here, we examined the function of the central nervous system (CNS) in five species of Drosophila with different heat tolerances, while they were exposed to either constant high temperature or a gradually increasing temperature (ramp). Tolerant species were able to preserve CNS function at higher temperatures and for longer durations than sensitive species, and similar differences were found for the behavioural indices (loss of coordination and onset of heat coma). Furthermore, the timing and temperature (constant and ramp exposure, respectively) for loss of coordination or complete coma coincided with the occurrence of spreading depolarisation (SD) events in the CNS. These SD events disrupt neurological function and silence the CNS, suggesting that CNS failure is the primary cause of impaired coordination and heat coma. Heat mortality occurs soon after heat coma in insects; to examine whether CNS failure could also be the proximal cause of heat death, we used selective heating of the head (CNS) and abdomen (visceral tissues). When comparing the temperature causing 50% mortality (LT50) of each body part versus that of the whole animal, we found that the head was not particularly heat sensitive compared with the abdomen. Accordingly, it is unlikely that nervous failure is the principal/proximate cause of heat mortality in Drosophila.
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Affiliation(s)
- Lisa B Jørgensen
- Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark
| | | | - Johannes Overgaard
- Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark
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12
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Lecheta MC, Awde DN, O’Leary TS, Unfried LN, Jacobs NA, Whitlock MH, McCabe E, Powers B, Bora K, Waters JS, Axen HJ, Frietze S, Lockwood BL, Teets NM, Cahan SH. Integrating GWAS and Transcriptomics to Identify the Molecular Underpinnings of Thermal Stress Responses in Drosophila melanogaster. Front Genet 2020; 11:658. [PMID: 32655626 PMCID: PMC7324644 DOI: 10.3389/fgene.2020.00658] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 05/29/2020] [Indexed: 12/12/2022] Open
Abstract
Thermal tolerance of an organism depends on both the ability to dynamically adjust to a thermal stress and preparatory developmental processes that enhance thermal resistance. However, the extent to which standing genetic variation in thermal tolerance alleles influence dynamic stress responses vs. preparatory processes is unknown. Here, using the model species Drosophila melanogaster, we used a combination of Genome Wide Association mapping (GWAS) and transcriptomic profiling to characterize whether genes associated with thermal tolerance are primarily involved in dynamic stress responses or preparatory processes that influence physiological condition at the time of thermal stress. To test our hypotheses, we measured the critical thermal minimum (CTmin) and critical thermal maximum (CTmax) of 100 lines of the Drosophila Genetic Reference Panel (DGRP) and used GWAS to identify loci that explain variation in thermal limits. We observed greater variation in lower thermal limits, with CTmin ranging from 1.81 to 8.60°C, while CTmax ranged from 38.74 to 40.64°C. We identified 151 and 99 distinct genes associated with CTmin and CTmax, respectively, and there was strong support that these genes are involved in both dynamic responses to thermal stress and preparatory processes that increase thermal resistance. Many of the genes identified by GWAS were involved in the direct transcriptional response to thermal stress (72/151 for cold; 59/99 for heat), and overall GWAS candidates were more likely to be differentially expressed than other genes. Further, several GWAS candidates were regulatory genes that may participate in the regulation of stress responses, and gene ontologies related to development and morphogenesis were enriched, suggesting many of these genes influence thermal tolerance through effects on development and physiological status. Overall, our results suggest that thermal tolerance alleles can influence both dynamic plastic responses to thermal stress and preparatory processes that improve thermal resistance. These results also have utility for directly comparing GWAS and transcriptomic approaches for identifying candidate genes associated with thermal tolerance.
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Affiliation(s)
- Melise C. Lecheta
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - David N. Awde
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - Thomas S. O’Leary
- Department of Biology, University of Vermont, Burlington, VT, United States
| | - Laura N. Unfried
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - Nicholas A. Jacobs
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - Miles H. Whitlock
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - Eleanor McCabe
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - Beck Powers
- Department of Biology, University of Vermont, Burlington, VT, United States
| | - Katie Bora
- Department of Biology, University of Vermont, Burlington, VT, United States
| | - James S. Waters
- Department of Biology, Providence College, Providence, RI, United States
| | - Heather J. Axen
- Department of Biology and Biomedical Sciences, Salve Regina College, Providence, RI, United States
| | - Seth Frietze
- Department of Biomedical and Health Sciences, University of Vermont, Burlington, VT, United States
| | - Brent L. Lockwood
- Department of Biology, University of Vermont, Burlington, VT, United States
| | - Nicholas M. Teets
- Department of Entomology, University of Kentucky, Lexington, KY, United States
| | - Sara H. Cahan
- Department of Biology, University of Vermont, Burlington, VT, United States
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13
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Tonione MA, Cho SM, Richmond G, Irian C, Tsutsui ND. Intraspecific variation in thermal acclimation and tolerance between populations of the winter ant, Prenolepis imparis. Ecol Evol 2020; 10:4749-4761. [PMID: 32551058 PMCID: PMC7297759 DOI: 10.1002/ece3.6229] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 11/30/2019] [Accepted: 03/09/2020] [Indexed: 01/17/2023] Open
Abstract
Thermal phenotypic plasticity, otherwise known as acclimation, plays an essential role in how organisms respond to short-term temperature changes. Plasticity buffers the impact of harmful temperature changes; therefore, understanding variation in plasticity in natural populations is crucial for understanding how species will respond to the changing climate. However, very few studies have examined patterns of phenotypic plasticity among populations, especially among ant populations. Considering that this intraspecies variation can provide insight into adaptive variation in populations, the goal of this study was to quantify the short-term acclimation ability and thermal tolerance of several populations of the winter ant, Prenolepis imparis. We tested for correlations between thermal plasticity and thermal tolerance, elevation, and body size. We characterized the thermal environment both above and below ground for several populations distributed across different elevations within California, USA. In addition, we measured the short-term acclimation ability and thermal tolerance of those populations. To measure thermal tolerance, we used chill-coma recovery time (CCRT) and knockdown time as indicators of cold and heat tolerance, respectively. Short-term phenotypic plasticity was assessed by calculating acclimation capacity using CCRT and knockdown time after exposure to both high and low temperatures. We found that several populations displayed different chill-coma recovery times and a few displayed different heat knockdown times, and that the acclimation capacities of cold and heat tolerance differed among most populations. The high-elevation populations displayed increased tolerance to the cold (faster CCRT) and greater plasticity. For high-temperature tolerance, we found heat tolerance was not associated with altitude; instead, greater tolerance to the heat was correlated with increased plasticity at higher temperatures. These current findings provide insight into thermal adaptation and factors that contribute to phenotypic diversity by revealing physiological variance among populations.
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Affiliation(s)
- Maria Adelena Tonione
- Department of Environmental Science, Policy, and ManagementUniversity of California‐BerkeleyBerkeleyCAUSA
| | - So Mi Cho
- Department of Environmental Science, Policy, and ManagementUniversity of California‐BerkeleyBerkeleyCAUSA
- Present address:
Department of Preventive MedicineYonsei University College of MedicineSeoulKorea
| | - Gary Richmond
- Department of Environmental Science, Policy, and ManagementUniversity of California‐BerkeleyBerkeleyCAUSA
- Present address:
Department of Family Health Care NursingUCSF School of NursingSan FranciscoCAUSA
| | - Christian Irian
- Department of Environmental Science, Policy, and ManagementUniversity of California‐BerkeleyBerkeleyCAUSA
| | - Neil Durie Tsutsui
- Department of Environmental Science, Policy, and ManagementUniversity of California‐BerkeleyBerkeleyCAUSA
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Lubawy J, Urbański A, Colinet H, Pflüger HJ, Marciniak P. Role of the Insect Neuroendocrine System in the Response to Cold Stress. Front Physiol 2020; 11:376. [PMID: 32390871 PMCID: PMC7190868 DOI: 10.3389/fphys.2020.00376] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 03/30/2020] [Indexed: 12/25/2022] Open
Abstract
Insects are the largest group of animals. They are capable of surviving in virtually all environments from arid deserts to the freezing permafrost of polar regions. This success is due to their great capacity to tolerate a range of environmental stresses, such as low temperature. Cold/freezing stress affects many physiological processes in insects, causing changes in main metabolic pathways, cellular dehydration, loss of neuromuscular function, and imbalance in water and ion homeostasis. The neuroendocrine system and its related signaling mediators, such as neuropeptides and biogenic amines, play central roles in the regulation of the various physiological and behavioral processes of insects and hence can also potentially impact thermal tolerance. In response to cold stress, various chemical signals are released either via direct intercellular contact or systemically. These are signals which regulate osmoregulation - capability peptides (CAPA), inotocin (ITC)-like peptides, ion transport peptide (ITP), diuretic hormones and calcitonin (CAL), substances related to the general response to various stress factors - tachykinin-related peptides (TRPs) or peptides responsible for the mobilization of body reserves. All these processes are potentially important in cold tolerance mechanisms. This review summarizes the current knowledge on the involvement of the neuroendocrine system in the cold stress response and the possible contributions of various signaling molecules in this process.
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Affiliation(s)
- Jan Lubawy
- Department of Animal Physiology and Development, Faculty of Biology, Institute of Experimental Biology, Adam Mickiewicz University Poznań, Poznań, Poland
| | - Arkadiusz Urbański
- Department of Animal Physiology and Development, Faculty of Biology, Institute of Experimental Biology, Adam Mickiewicz University Poznań, Poznań, Poland
- HiProMine S.A., Robakowo, Poland
| | - Hervé Colinet
- ECOBIO – UMR 6553, Université de Rennes 1, CNRS, Rennes, France
| | | | - Paweł Marciniak
- Department of Animal Physiology and Development, Faculty of Biology, Institute of Experimental Biology, Adam Mickiewicz University Poznań, Poznań, Poland
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15
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Robertson RM, Dawson-Scully KD, Andrew RD. Neural shutdown under stress: an evolutionary perspective on spreading depolarization. J Neurophysiol 2020; 123:885-895. [PMID: 32023142 PMCID: PMC7099469 DOI: 10.1152/jn.00724.2019] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 01/13/2020] [Accepted: 01/14/2020] [Indexed: 11/22/2022] Open
Abstract
Neural function depends on maintaining cellular membrane potentials as the basis for electrical signaling. Yet, in mammals and insects, neuronal and glial membrane potentials can reversibly depolarize to zero, shutting down neural function by the process of spreading depolarization (SD) that collapses the ion gradients across membranes. SD is not evident in all metazoan taxa with centralized nervous systems. We consider the occurrence and similarities of SD in different animals and suggest that it is an emergent property of nervous systems that have evolved to control complex behaviors requiring energetically expensive, rapid information processing in a tightly regulated extracellular environment. Whether SD is beneficial or not in mammals remains an open question. However, in insects, it is associated with the response to harsh environments and may provide an energetic advantage that improves the chances of survival. The remarkable similarity of SD in diverse taxa supports a model systems approach to understanding the mechanistic underpinning of human neuropathology associated with migraine, stroke, and traumatic brain injury.
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Affiliation(s)
- R Meldrum Robertson
- Department of Biology and Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - Ken D Dawson-Scully
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida
| | - R David Andrew
- Department of Biomedical and Molecular Sciences and Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
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16
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Kawarasaki Y, Welle AM, Elnitsky MA. Is rapid cold-hardening an aerobic process? Characterization of changes in metabolic activity during its induction and effects of anoxia in flesh fly. JOURNAL OF INSECT PHYSIOLOGY 2020; 120:103996. [PMID: 31837292 DOI: 10.1016/j.jinsphys.2019.103996] [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: 09/06/2019] [Revised: 12/06/2019] [Accepted: 12/09/2019] [Indexed: 06/10/2023]
Abstract
Rapid cold-hardening (RCH) is a type of phenotypic plasticity that promotes a swift improvement of cold tolerance in insects. A brief exposure to mild cold dramatically increases insect survival to a subsequent cold exposure that would be lethal otherwise. In adult male flesh fly, Sarcophaga bullata, as little as 15 min at 5 °C significantly improved organismal survival at -7°C from 0 to 66.7 ± 11.1%. In this study, we investigated whether this RCH response is an aerobic process in S. bullata by characterizing changes in metabolic activity during its induction. At the level of whole organism, CO2 production continued at a level above our detection limit, and a relatively greater rate was observed during the early phase before it stabilized after ~1 h of the RCH induction. Similarly, in isolated flight muscle tissues, those maintained at 5 °C for 10 min exhibited significantly greater rates of oxygen consumption, compared to those maintained at 5 °C for 1 h (2.82 ± 0.29 vs. 1.36 ± 0.22 μl O2 mg-1 DM h-1). When these tissues were exposed to LaCl3, a treatment that should inhibit RCH ex vivo, oxygen consumption rates of the muscles were reduced significantly to a level similar to those that had been maintained at 5 °C for 1 h. Interestingly, however, the RCH response was still evident among individuals exposed to chilling under anoxia. Compared to those exposed to anoxia for 30 min only at 25 °C, flies exposed to 5 °C for 2 h under anoxia following the initial exposure exhibited a significantly greater level of cold tolerance at -7.5 °C (41.7 ± 7.1 vs. 91.8 ± 3.9%). Our results suggest that while relatively greater rates of metabolic activity are associated with the early phase of the RCH induction, it can proceed under the anoxic condition, thereby suggesting its independence to aerobic respiration.
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Affiliation(s)
- Yuta Kawarasaki
- Department of Biology, Gustavus Adolphus College, Saint Peter, MN 56082, USA.
| | - Alyssa M Welle
- Department of Biology, Gustavus Adolphus College, Saint Peter, MN 56082, USA
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17
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Srithiphaphirom P, Lavallee S, Robertson RM. Rapid cold hardening and octopamine modulate chill tolerance in Locusta migratoria. Comp Biochem Physiol A Mol Integr Physiol 2019; 234:28-35. [PMID: 30991118 DOI: 10.1016/j.cbpa.2019.04.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 04/09/2019] [Accepted: 04/11/2019] [Indexed: 12/13/2022]
Abstract
Temperature has profound effects on the neural function and behaviour of insects. When exposed to low temperature, chill-susceptible insects enter chill coma, a reversible state of neuromuscular paralysis. Despite the popularity of studying the effects of low temperature on insects, we know little about the physiological mechanisms controlling the entry to, and recovery from, chill coma. Spreading depolarization (SD) is a phenomenon that causes a neural shutdown in the central nervous system (CNS) and it is associated with a loss of K+ homeostasis in the CNS. Here, we investigated the effects of rapid cold hardening (RCH) on chill tolerance of the migratory locust. With an implanted thermocouple in the thorax, we determined the temperature associated with a loss of responsiveness (i.e. the critical thermal minimum - CTmin) in intact male adult locusts. In parallel experiments, we recorded field potential (FP) in the metathoracic ganglion (MTG) of semi-intact preparations to determine the temperature that would induce neural shutdown. We found that SD in the CNS causes a loss of coordinated movement immediately prior to chill coma and RCH reduces the temperature that evokes neural shutdown. Additionally, we investigated a role for octopamine (OA) in the locust chill tolerance and found that OA reduces the CTmin and mimics the effects of prior stress (anoxia) in locust.
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Affiliation(s)
| | - Sarah Lavallee
- Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada
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18
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Andersen MK, Overgaard J. The central nervous system and muscular system play different roles for chill coma onset and recovery in insects. Comp Biochem Physiol A Mol Integr Physiol 2019; 233:10-16. [PMID: 30910613 DOI: 10.1016/j.cbpa.2019.03.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 02/05/2019] [Accepted: 03/18/2019] [Indexed: 01/03/2023]
Abstract
When insects are cooled, they initially lose their ability to perform coordinated movements at their critical thermal minima (CTmin). At a slightly lower temperature, they enter a state of complete paralysis (chill coma onset temperature - CCO) and if they are returned to permissive temperatures they regain function after a recovery period which is termed chill coma recovery time (CCRT). These three phenotypes (CTmin, CCO, and CCRT) are all popular measures of insect cold tolerance and it is therefore important to characterize the physiological processes that are responsible for these phenotypes. In the present study we measured extracellular field potentials in the central nervous system (CNS) and muscle membrane potential (Vm) during cooling and recovery in three Drosophila species that have different cold tolerances. With these measurements we assess the role of the CNS and muscle Vm in setting the lower thermal limits (CTmin and CCO) and in delaying chill coma recovery (CCRT). The experiments suggest that entry into chill coma is primarily caused by the onset of a spreading depolarization in the CNS for all three species. In the two most cold-sensitive species we observed that the loss of CNS function was followed closely by a depolarization of muscle Vm which is known to compromise muscle function. When flies are returned to benign temperature after a cold exposure we observe a rapid recovery of CNS function, but functional recovery was delayed by a slower recovery of muscle polarization. Thus, we demonstrate the primacy of different physiological systems (CNS vs. muscle) as determinants of the most commonly used cold tolerance measures for insects (CTmin vs. CCRT).
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Affiliation(s)
| | - Johannes Overgaard
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
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Giraldo D, Adden A, Kuhlemann I, Gras H, Geurten BRH. Correcting locomotion dependent observation biases in thermal preference of Drosophila. Sci Rep 2019; 9:3974. [PMID: 30850647 PMCID: PMC6408449 DOI: 10.1038/s41598-019-40459-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 02/18/2019] [Indexed: 11/21/2022] Open
Abstract
Sensing environmental temperatures is essential for the survival of ectothermic organisms. In Drosophila, two of the most used methodologies to study temperature preferences (TP) and the genes involved in thermosensation are two-choice assays and temperature gradients. Whereas two-choice assays reveal a relative TP, temperature gradients can identify the absolute Tp. One drawback of gradients is that small ectothermic animals are susceptible to cold-trapping: a physiological inability to move at the cold area of the gradient. Often cold-trapping cannot be avoided, biasing the resulting TP to lower temperatures. Two mathematical models were previously developed to correct for cold-trapping. These models, however, focus on group behaviour which can lead to overestimation of cold-trapping due to group aggregation. Here we present a mathematical model that simulates the behaviour of individual Drosophila in temperature gradients. The model takes the spatial dimension and temperature difference of the gradient into account, as well as the rearing temperature of the flies. Furthermore, it allows the quantification of cold-trapping and reveals unbiased TP. Additionally, our model reveals that flies have a range of tolerable temperatures, and this measure is more informative about the behaviour than commonly used TP. Online simulation is hosted at http://igloo.uni-goettingen.de. The code can be accessed at https://github.com/zerotonin/igloo.
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Affiliation(s)
- Diego Giraldo
- Department for Cellular Neurobiology, Institute for Zoology and Anthropology, Georg-August University Göttingen, Göttingen, Germany
| | - Andrea Adden
- Department for Cellular Neurobiology, Institute for Zoology and Anthropology, Georg-August University Göttingen, Göttingen, Germany.,Vision Group, Department of Biology, Lund University, Lund, Sweden
| | - Ilyas Kuhlemann
- Department for Biophysical Chemistry, Institute for Physical Chemistry, Georg-August University Göttingen, Göttingen, Germany
| | - Heribert Gras
- Department for Cellular Neurobiology, Institute for Zoology and Anthropology, Georg-August University Göttingen, Göttingen, Germany
| | - Bart R H Geurten
- Department for Cellular Neurobiology, Institute for Zoology and Anthropology, Georg-August University Göttingen, Göttingen, Germany.
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20
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Robertson RM, Cease AJ, Simpson SJ. Anoxia tolerance of the adult Australian Plague Locust (Chortoicetes terminifera). Comp Biochem Physiol A Mol Integr Physiol 2019; 229:81-92. [DOI: 10.1016/j.cbpa.2018.12.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 12/07/2018] [Accepted: 12/09/2018] [Indexed: 12/17/2022]
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Garcia MJ, Teets NM. Cold stress results in sustained locomotor and behavioral deficits in Drosophila melanogaster. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2019; 331:192-200. [PMID: 30609298 DOI: 10.1002/jez.2253] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/06/2018] [Accepted: 12/07/2018] [Indexed: 12/19/2022]
Abstract
Tolerance of climatic stressors is an important predictor of the current distribution of insect species, their potential to invade new environments, and their responses to rapid climate change. Cold stress causes acute injury to nerves and muscles, and here we tested the hypothesis that low temperature causes sublethal deficits in locomotor behaviors that are dependent on neuromuscular function. To do so, we applied a previously developed assay, the rapid iterative negative geotaxis (RING) assay, to investigate behavioral consequences of cold stress in Drosophila melanogaster. The RING assay allows for rapid assessment of negative geotaxis behavior by quantifying climbing height and willingness to climb after cold stress. We exposed flies to cold stress at 0°C and assessed the extent to which duration of cold stress, recovery time, and cold acclimation influenced climbing performance. There was a clear dose-response relationship between cold exposure and performance deficits, with climbing height and willingness decreasing as cold exposure increased from 2 to 24 hr. Following cold exposure of an intermediate duration (12 hr), climbing height and willingness gradually improved as recovery time increased from 4 to 72 hr but flies never fully recovered. Finally, cold acclimation improved overall climbing height and willingness in both untreated and cold-stressed flies but did not prevent a reduction in climbing performance. Thus, cold stress causes deficits in locomotor and behavior that are dependent on the dose of cold exposure and persist long after the stress subsides. These results likely have implications for the ecological and evolutionary responses of insect populations to thermally variable environments.
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Affiliation(s)
- Mark J Garcia
- Department of Entomology, College of Agriculture, Food, and Environment, University of Kentucky, Lexington, Kentucky
| | - Nicholas M Teets
- Department of Entomology, College of Agriculture, Food, and Environment, University of Kentucky, Lexington, Kentucky
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22
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Loss of ion homeostasis is not the cause of chill coma or impaired dispersal in false codling moth Thaumatotibia leucotreta (Lepidoptera: Tortricidae). Comp Biochem Physiol A Mol Integr Physiol 2018; 229:40-44. [PMID: 30502471 DOI: 10.1016/j.cbpa.2018.11.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/20/2018] [Accepted: 11/21/2018] [Indexed: 11/23/2022]
Abstract
Dispersal is a central requirement of a successful sterile insect release programme, but field-released false codling moth (FCM) typically suffer from poor dispersal ability, especially at low ambient temperatures. Here we test the hypothesis that poor activity and dispersal in FCM is caused by delayed or perturbed recovery of ion and/or water homeostasis after chilling for handling and transport prior to field release. Hemolymph and flight muscle were collected from two treatment groups at three time points that targeted thermal conditions above and below the chill coma induction threshold of ~ 6 °C: 1) control moths kept at 25 °C, 2) moths exposed to 3 °C or 9 °C for 4 h, and 3) moths allowed to recover at 25 °C for 24 h after exposure to either 3 °C or 9 °C. We measured concentrations of Na+, K+ and Mg2+ in the hemolymph and muscle collected at each time point. Exposure to a chill-coma inducing temperature had little effect overall on ion balance in the hemolymph and flight muscle of false codling moth, but hemolymph [Na+] decreased from 10.4 ± 0.4 mM to 6.9 ± 0.7 mM as moths were chilled to 3 °C and then increased to 10.4 ± 0.9 mM after the 24 h recovery period. In the 9 °C cooling treatment, [K+] increased from 8.2 ± 0.5 mM during chilling to 14.1 ± 1.9 mM after the 24 h recovery period. No changes were seen in equilibrium potentials in either of the ions measured. Thus, we did not find evidence that water and ion homeostasis are lost by the moths in chill coma and conclude that reduced dispersal in field-released moths is not direct a consequence of the costs of re-establishment of homeostasis.
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23
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Colinet H, Rinehart JP, Yocum GD, Greenlee KJ. Mechanisms underpinning the beneficial effects of fluctuating thermal regimes in insect cold tolerance. J Exp Biol 2018; 221:221/14/jeb164806. [DOI: 10.1242/jeb.164806] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
ABSTRACT
Insects exposed to low temperature often have high mortality or exhibit sublethal effects. A growing number of recent studies have shown beneficial effects of exposing insects to recurrent brief warm pulses during low-temperature stress (fluctuating thermal regime, FTR). The physiological underpinnings of the beneficial effects of FTR on cold survival have been extensively studied over the past few years. Profiling with various ‘-omics’ techniques has provided supporting evidence for different physiological responses between insects exposed to FTR and constant low temperature. Evidence from transcriptomic, metabolomic and lipidomic studies points to a system-wide loss of homeostasis at low temperature that can be counterbalanced by repair mechanisms under FTR. Although there has been considerable progress in understanding the physiological mechanisms underlying the beneficial effects of FTR, here we discuss how many areas still lack clarity, such as the precise role(s) of heat shock proteins, compatible solutes or the identification of regulators and key players involved in the observed homeostatic responses. FTR can be particularly beneficial in applied settings, such as for model insects used in research, integrated pest management and pollination services. We also explain how the application of FTR techniques in large-scale facilities may require overcoming some logistical and technical constraints. FTR definitively enhances survival at low temperature in insects, but before it can be widely used, we suggest that the possible fitness and energy costs of FTR must be explored more thoroughly. Although FTR is not ecologically relevant, similar processes may operate in settings where temperatures fluctuate naturally.
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Affiliation(s)
- Hervé Colinet
- Univ Rennes, CNRS, ECOBIO-UMR 6553, 263 Ave du Général Leclerc, 35042 Rennes, France
| | - Joseph P. Rinehart
- USDA-ARS Red River Valley Agricultural Research Center, Biosciences Research Laboratory, 1605 Albrecht Boulevard, Fargo, ND 58102-2765, USA
| | - George D. Yocum
- USDA-ARS Red River Valley Agricultural Research Center, Biosciences Research Laboratory, 1605 Albrecht Boulevard, Fargo, ND 58102-2765, USA
| | - Kendra J. Greenlee
- Department of Biological Sciences, PO Box 6050, Dept 2715, North Dakota State University, Fargo, ND 58108-6050, USA
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Knight K. Central nervous system shutdown causes cold flies to keel over. J Exp Biol 2018. [DOI: 10.1242/jeb.184929] [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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