Mechanisms to reduce dehydration stress in larvae of the Antarctic midge, Belgica antarctica

The Antarctic midge, Belgica antarctica, is exposed to frequent periods of dehydration during its prolonged larval development in the cold and dry Antarctic environment. In this study, we determined the water requirements of the larvae and the mechanisms it exploits to reduce the stress of drying. Larvae lost water at an exceptionally high rate (>10%/h) and tolerated losing a high portion (>70%) of their water content. Larvae were unable to absorb water from subsaturated water vapor (< or = 0.98 a(v)) to replenish their water stores, thus this midge relies exclusively on the intake of liquid water to increase its pool of body water and maintain water balance. To reduce dehydration stress, the midge employed a variety of mechanisms. Behaviorally, the larvae suppressed water loss by clustering. In response to slow dehydration, glycerol concentration increased 2-fold and trehalose concentration increased 3-fold, responses that are known to decrease the rate of water loss and increase dehydration tolerance. No changes in the mass of cuticular lipids occurred in response to desiccation, but the observed shift to longer hydrocarbons likely contributes to reduced water loss as the larvae dehydrate. As the larvae dehydrated, their oxygen consumption rate dropped, resulting in a reduction of water loss by respiration. Lastly, one bout of slow dehydration also enhanced the larva's ability to survive subsequent dehydration, suggesting that the larvae have the capacity for drought acclimation. Thus, these hydrophilic midge larvae prevent dehydration by multiple mechanisms that collectively reduce the water loss rate and increase dehydration tolerance.     

Knot formation reduces water exchange by adult males of the hairworm,Paragordius varius (Nematomorpha: Gordioidea)

To examine how aggregation by hairworms may enhance survival in freshwater, we determined water balance characteristics of Paragordius varius in groups of different sizes. P. varius is hyperosmotic resulting in high body water content and functions down to one-half of water stores. Absence of a critical transition temperature implies a watertight, low-porosity cuticle. Aggregated worms lose water slowly, as a physiological consequence of reduced motor activity. The water balance strategy shifts from a reliance on high dehydration tolerance for isolated individuals, affording high water loss rates, to suppressed activation energy when aggregated, wherein blocking water gain is important when water loss is slower. Low water loss rate derives from stillness and aggregating that facilitate mating or anti-predator defense, rather than as a behavior to regulate water loss. Presence of hairworms in streams is an indicator of high-quality water that is necessary to maintain water balance.     

The control of drinking in elasmobranch fish with special reference to the renin-angiotensin system

In summary, it is evident that teleost and elasmobranch fish respond to extra-cellular dehydration by increasing drinking rate mediated by an increase in circulating levels of ANG II. However, although the primary stimulus for drinking may be the same, clearly the mechanisms involved in regulating ion and water balance are entirely different. In order to maintain ion and water balance in the face of cellular and extra-cellular dehydration, the integration and hormonal control of renal and extra-renal function in elasmobranchs has developed in a very different manner to that described for teleost fish.     

Chill-tolerant Gryllus crickets maintain ion balance at low temperatures

Insect cold tolerance is both phenotypically-plastic and evolutionarily labile, but the mechanisms underlying this variation are uncertain. Chill-susceptible insects lose ion and water homeostasis in the cold, which contributes to the development of injuries and eventually death. We thus hypothesized that more cold-tolerant insects will better maintain ion and water balance at low temperatures. We used rapid cold-hardening (RCH) and cold acclimation to improve cold tolerance of male Gryllus pennsylvanicus, and also compared this species to its cold-tolerant relative (Gryllus veletis). Cold acclimation and RCH decreased the critical thermal minimum (CT_min) and chill coma recovery time (CCR) in G. pennsylvanicus, but while cold acclimation improved survival of 0 °C, RCH did not; G. veletis was consistently more cold-tolerant (and had lower CCR and CT_min) than G. pennsylvanicus. During cold exposure, hemolymph water and Na⁺ migrated to the gut of warm-acclimated G. pennsylvanicus, which increased hemolymph [K⁺] and decreased muscle K⁺ equilibrium potentials. By contrast, cold-acclimated G. pennsylvanicus suffered a smaller loss of ion and water homeostasis during cold exposure, and this redistribution did not occur at all in cold-exposed G. veletis. The loss of ion and water balance was similar between RCH and warm-acclimated G. pennsylvanicus, suggesting that different mechanisms underlie decreased CCR and CT_min compared to increased survival at 0 °C. We conclude that increased tolerance of chilling is associated with improved maintenance of ion and water homeostasis in the cold, and that this is consistent for both phenotypic plasticity and evolved cold tolerance.     

Heat stress is associated with disruption of ion balance in the migratory locust,Locusta migratoria

Thermal tolerance is important in determining the spatial and temporal distributions of insects but the mechanisms which determine upper thermal limits remain poorly understood. In terrestrial insects heat tolerance is unlikely to be limited by oxygen supply but in some arthropods, heat stress has been shown to cause haemolymph hyperkalaemia which is known to have detrimental effects on neuromuscular excitability. It is however unresolved if heat-induced hyperkalemia is the cause or the result of cellular heat injury. To address the putative role of heat-induced hyperkalemia we quantified changes in ion and water balance in haemolymph and muscle tissue of the migratory locust during exposure to two static temperatures clustered around the CT_max (48 °C and 50 °C). We show that heat stress caused a loss of ion balance and severe haemolymph hyperkalaemia which coincided with the onset of heat stupor. Locusts were able to maintain their haemolymph volume throughout exposure, suggesting it is unlikely that osmoregulatory failure is responsible for haemolymph hyperkalaemia. When locusts were allowed to recover from heat stupor, they recovered ion balance quickly but were still unable to function optimally after 24 h. The results therefore indicate that both the haemolymph hyperkalaemia and associated depression of muscular function (heat stupor) are secondary results of cellular heat injury and that the cause of heat stupor most be sought elsewhere.     

昆虫抗冻蛋白的研究进展

热滞效应(Tberm Hysteresis Action)最早在昆虫研究中发现,后来研究表明,它是抗冻蛋白(Antifreeze Proteins,AFPs)的一种基本性质。和鱼类,植物AFPs相比,昆虫AFPs具有更高 的热滞活性和独特的化学结构特征。昆虫AFPs在昆虫抗冻生理过程中起着相当重要的作用,表现在以下三个方面：①抑制一些冰晶形成;②提高冰冻耐受性;③可能参与水分平衡过程。光周期,气温和湿度是调控AFPs生物合成与降解的三种外部因子,而体内激素的变化可能是直接调节脂肪体合成AFPs的内部因子。     

植物盐胁迫应答蛋白质组学分析

土壤盐渍化是限制植物生长和分布的关键因素之一,揭示植物盐胁迫应答的分子机理是借助分子生物学手段提高植物耐盐性的基础.近年来,人们利用高通量蛋白质组学技术分析了拟南芥、水稻等19种植物的盐胁迫应答蛋白质表达图谱.从植物类群(盐生植物和甜土植物)、组织器官(根、地上部分/茎、胚根和胚轴、叶片、花序和配子体)、细胞(悬浮培养细胞、愈伤组织细胞和单细胞生物)和亚细胞结构(叶绿体、质膜和质外体)几方面整合分析了植物盐胁迫应答蛋白质组表达模式特征,主要特征包括:(1)盐生植物通过全面调节细胞骨架重塑、离子转运和区隔化、渗透平衡、活性氧(ROS)清除、信号转导、光合作用和能量代谢等信号与代谢网络体系,获得相对较高的抗/耐盐能力;(2)植物地上部分(叶片、茎、配子体)或光合组织细胞(悬浮培养细胞、愈伤组织细胞和单细胞盐藻)通过调节参与光合作用、碳和能量代谢、ROS清除过程蛋白质的表达模式应对盐胁迫环境;(3)植物地下部分(根、胚根)通过调控信号转导和离子转运相关蛋白质感知/传递盐胁迫信号并维持离子平衡;(4)花序中参与渗透调节、转录调控、蛋白质加工和ROS清除的蛋白质在盐胁迫条件下变化显著;(5)叶绿体通过调控参与光合作用、蛋白质加工和周转,以及氧化还原系统平衡等过程应对盐胁迫;(6)质外体中参与细胞壁代谢、胁迫防御和信号转导过程的蛋白质受盐胁迫影响明显;(7)细胞膜中参与维持膜结构稳定、物质/离子运输和信号转导过程的蛋白质对植物盐胁迫应答具有重要作用.这些分析为深入研究植物耐盐的分子机制提供了重要信息.     

Validity of thermal ramping assays used to assess thermal tolerance in arthropods

Proper assessment of environmental resistance of animals is critical for the ability of researchers to understand how variation in environmental conditions influence population and species abundance. This is also the case for studies of upper thermal limits in insects, where researchers studying animals under laboratory conditions must select appropriate methodology on which conclusions can be drawn. Ideally these methods should precisely estimate the trait of interest and also be biological meaningful. In an attempt to develop such tests it has been proposed that thermal ramping assays are useful assays for small insects because they incorporate an ecologically relevant gradual temperature change. However, recent model-based papers have suggested that estimates of thermal resistance may be strongly confounded by simultaneous starvation and dehydration stress. In the present study we empirically test these model predictions using two sets of independent experiments. We clearly demonstrate that results from ramping assays of small insects (Drosophila melanogaster) are not compromised by starvation- or dehydration-stress. Firstly we show that the mild disturbance of water and energy balance of D. melanogaster experienced during the ramping tests does not confound heat tolerance estimates. Secondly we show that flies pre-exposed to starvation and dehydration have "normal" heat tolerance and that resistance to heat stress is independent of the energetic and water status of the flies. On the basis of our results we discuss the assumptions used in recent model papers and present arguments as to why the ramping assay is both a valid and ecologically relevant way to measure thermal resistance in insects.     

Concurrent effects of cold and hyperkalaemia cause insect chilling injury

Chilling injury and death are the ultimate consequence of low temperature exposure for chill susceptible insects, and low temperature tolerance is considered one of the most important factors determining insect distribution patterns. The physiological mechanisms that cause chilling injury are unknown, but chronic cold exposure that causes injury is consistently associated with elevated extracellular [K⁺], and cold tolerant insects possess a greater capacity to maintain ion balance at low temperatures. Here, we use the muscle tissue of the migratory locust (Locusta migratoria) to examine whether chill injury occurs during cold exposure or following return to benign temperature and we specifically examine if elevated extracellular [K⁺], low temperature, or a combination thereof causes cell death. We find that in vivo chill injury occurs during the cold exposure (when extracellular [K⁺] is high) and that there is limited capacity for repair immediately following the cold stress. Further, we demonstrate that that high extracellular [K⁺] causes cell death in situ, but only when experienced at low temperatures. These findings strongly suggest that that the ability to maintain ion (particularly K⁺) balance is critical to insect low temperature survival, and highlight novel routes of study in the mechanisms regulating cell death in insects in the cold.     

Physiological ecology of aquatic overwintering in ranid frogs

In cold-temperate climates, overwintering aquatic ranid frogs must survive prolonged periods of low temperature, often accompanied by low levels of dissolved oxygen. They must do so with the energy stores acquired prior to the onset of winter. Overwintering mortality is a significant factor in their life history, occasionally reaching 100% due to freezing and/or anoxia. Many species of northern ranid frogs overwinter in the tadpole stage, which increases survival during hypoxic episodes relative to adults, as well as allowing for larger sizes at metamorphosis. At temperatures below 5 degrees C, submerged ranid frogs are capable of acquiring adequate oxygen via cutaneous gas exchange over a wide range of ambient oxygen partial pressures (PO(2)), and possess numerous physiological and behavioural mechanisms that allow them to maintain normal rates of oxygen uptake across the skin at a relatively low PO(2). At levels of oxygen near and below the critical PO(2) that allows for aerobic metabolism, frogs must adopt biochemical mechanisms that act to minimise oxygen utilisation and assist in maintaining an aerobic state to survive overwintering. These mechanisms include alterations in mitochondrial metabolism and affinity, changes in membrane permeability, alterations in water balance, and reduction in cellular electrochemical gradients, all of which lead to an overall reduction in whole-animal metabolism. Winter energetic requirements are fueled by the energy stores in liver, muscle, and fat depots, which are likely to be sufficient when the water is cold and well oxygenated. However, under hypoxic conditions fat stores cannot be utilised efficiently and glycogen stores are used up rapidly due to recruitment of anaerobiosis. Since ranid frogs have minimal tolerance to anoxia, it is untenable to suggest that they spend a significant portion of the winter buried in anoxic mud, but instead utilise a suite of behavioural and physiological mechanisms geared to optimal survival in cold, hypoxic conditions.     

Cold adaptation shapes the robustness of metabolic networks in Drosophila melanogaster

When ectotherms are exposed to low temperatures, they enter a cold‐induced coma (chill coma) that prevents resource acquisition, mating, oviposition, and escape from predation. There is substantial variation in time taken to recover from chill coma both within and among species, and this variation is correlated with habitat temperatures such that insects from cold environments recover more quickly. This suggests an adaptive response, but the mechanisms underlying variation in recovery times are unknown, making it difficult to decisively test adaptive hypotheses. We use replicated lines of Drosophila melanogaster selected in the laboratory for fast (hardy) or slow (susceptible) chill‐coma recovery times to investigate modifications to metabolic profiles associated with cold adaptation. We measured metabolite concentrations of flies before, during, and after cold exposure using nuclear magnetic resonance (NMR) spectroscopy to test the hypotheses that hardy flies maintain metabolic homeostasis better during cold exposure and recovery, and that their metabolic networks are more robust to cold‐induced perturbations. The metabolites of cold‐hardy flies were less cold responsive and their metabolic networks during cold exposure were more robust, supporting our hypotheses. Metabolites involved in membrane lipid synthesis, tryptophan metabolism, oxidative stress, energy balance, and proline metabolism were altered by selection on cold tolerance. We discuss the potential significance of these alterations.     

ADAPTATIONS OF TERRESTRIAL ARTHROPODS TO THE ALPINE ENVIRONMENT

1. The climate changes drastically above the timberline. Diverse adaptations have been evolved by insects and other terrestrial arthropods to survive the alpine environment. The fitness of each species depends on a combination of different factors in accordance with their special habitats. 2. Morphological adaptations such as reduced body-size, are known from a number of alpine insects, increasing their possibility to find sheltered microhabitats. Selection for reduced body size in Andean Phulia spp. butterflies is probably a result of their rigorous environment. Wing atrophy, which is also known in insects from other extreme environments, is widespread in alpine species. In several terrestrial arthropods the absorption of solar radiation is increased by melanism. Increased pubescence, protecting against the loss of heat, is known in alpine butterflies and bumblebees. 3. Several behavioural adaptations are described. Thermoregulatory behaviour is important in many species to raise their body temperatures. Alpine butterflies orient the dark basis of their wings perpendicular to the rays of the sun. Body temperatures of 30 °C may be required for flight. To increase their activities many alpine terrestrial arthropods seek warmer microhabitats in the vegetation and under rocks. The adaptive advantage of nocturnal activity as observed in several species, may be to maintain the water balance or to avoid predation. 4. Tropical alpine terrestrial arthropods are faced with special problems. The large diel temperature fluctuations require cold-hardiness during the night and tolerance to heat during the day. Many species seek sheltered microhabitats under rocks and in vegetation. 5. Due to low precipitation and high evaporation rates many mountain areas are extremely dry. High resistance to desiccation may be very important to alpine species, and in particular to tropical species. Rates of water loss at low relative humidities are comparable to those of desert arthropods. 6. As an adaptation to the cold alpine summers several species of terrestrial arthropods require more than one year to complete their life-cycles. Special to these species is their adaptation to low temperatures in two or more overwintering stages. In spite of their cold surroundings several species have univoltine life cycles, frequently combined with highly specialized adaptations. Increased metabolic rates as a compensation to low temperatures may be widespread in alpine species, but few data are available. 7. Cold tolerance is of particular importance in temperature alpine species. Winter survival in Collembola and Acari depends on supercooling. Great seasonal variations have been observed in a number of species. Freezing tolerance is also known from alpine insects, e.g. in some species of beetles. At high latitudes alpine species must endure periods of up to eight or nine month at low temperatures during hibernation. Anaerobiosis is known from species that are enclosed in ice, with lactate as the main end product of metabolism.     

Mechanisms underlying insect freeze tolerance

Freeze tolerance – the ability to survive internal ice formation – has evolved repeatedly in insects, facilitating survival in environments with low temperatures and/or high risk of freezing. Surviving internal ice formation poses several challenges because freezing can cause cellular dehydration and mechanical damage, and restricts the opportunity to metabolise and respond to environmental challenges. While freeze‐tolerant insects accumulate many potentially protective molecules, there is no apparent ‘magic bullet’ – a molecule or class of molecules that appears to be necessary or sufficient to support this cold‐tolerance strategy. In addition, the mechanisms underlying freeze tolerance have been minimally explored. Herein, we frame freeze tolerance as the ability to survive a process: freeze‐tolerant insects must withstand the challenges associated with cooling (low temperatures), freezing (internal ice formation), and thawing. To do so, we hypothesise that freeze‐tolerant insects control the quality and quantity of ice, prevent or repair damage to cells and macromolecules, manage biochemical processes while frozen/thawing, and restore physiological processes post‐thaw. Many of the molecules that can facilitate freeze tolerance are also accumulated by other cold‐ and desiccation‐tolerant insects. We suggest that, when freezing offered a physiological advantage, freeze tolerance evolved in insects that were already adapted to low temperatures or desiccation, or in insects that could withstand small amounts of internal ice formation. Although freeze tolerance is a complex cold‐tolerance strategy that has evolved multiple times, we suggest that a process‐focused approach (in combination with appropriate techniques and model organisms) will facilitate hypothesis‐driven research to understand better how insects survive internal ice formation.     

Organismal Carbohydrate and Lipid Homeostasis

All living organisms maintain a high ATP:ADP ratio to drive energy-requiring processes. They therefore need mechanisms to maintain energy balance at the cellular level. In addition, multicellular eukaryotes have assigned the task of storing energy to specialized cells such as adipocytes, and therefore also need a means of intercellular communication to signal the needs of individual tissues and to maintain overall energy balance at the whole body level. Such signaling allows animals to survive periods of fasting or starvation when food is not available and is mainly achieved by hormonal and nervous communication. Insulin, adipokines, epinephrine, and other agonists thus stimulate pathways that regulate the activities of key enzymes involved in control of metabolism to integrate organismal carbohydrate and lipid metabolism. Overnutrition can dysregulate these pathways and have damaging consequences, causing insulin resistance and type 2 diabetes.     

Recent developments in understanding salinity tolerance

Salt stress imposes a major environmental threat to agriculture and its adverse impacts are getting more serious problem in regions where saline water is used for irrigation. Therefore, the efforts to increase salt tolerance of crop plants bear remarkable importance to supply sustainable agriculture on marginal lands and could potentially improve crop yield overall. Acclimation of plants to salinized conditions depend upon activation of cascades of molecular networks involved in stress sensing, signal transduction and the expression of specific stress-related genes and metabolites. Adaptational processes are elaborate and more than one gene might be expressed during the acclimation process. Isolation of Salt Overly Sensitive (SOS) genes by sos mutants shed us light on the relationship between ion homeostasis and salinity tolerance. The essential role of antioxidative system to maintain a balance between the overproduction of Reactive Oxygen Species (ROS) and their scavenging to keep them at signaling level for reinstating metabolic homeostasis has already been established. Compatible osmolytes synthesized to maintain equal water potential with the environment under salinity conditions implements another strategy to develop resistance against salinity. With the growing body of information about molecular markers, genomics and post-genomics and thus increasing understanding of signaling pathways and mechanisms that contributes to plant stress responses, significant breakthroughs have been emerged to figure out the mechanism and control of salinity tolerance at molecular level. Many transgenic works were carried out to produce transgenic plants to develop enhanced tolerance to salt stress. However, a few of them seem succeeded to be implemented in salt-affected marginal lands efficiently. This minireview focuses on the recent developments in salinity tolerance research aiming to contribute sustainable food production under salt stress in the face of a globally warming ecosystem.     

Water homeostasis in desert-dwelling horses

This study set out to investigate tolerance of the body water pool to short-term water deprivation in horses and, in particular, to assess whether feral horses from the Namib Desert showed tolerance to dehydration superior to Transvaal. Hydration status was compared in six feral horses from the Namib Desert and in six Boerperd farm horses under conditions of normal hydration and after 72 h of dehydration. Under normal hydration, the two groups did not differ significantly in water intake, plasma sodium and potassium concentrations, plasma osmolality, hematocrit, total plasma protein, body water content, or water turnover (ml.kg-0.82.day-1). The Namib horses were significantly smaller (P less than 0.0001) and turned over 5 liters less water per day than the Boerperd during normal hydration and 4 liters less during dehydration. Increases in plasma sodium concentration after 72 h of dehydration were greater (P less than 0.05) in the Namib horses. It was concluded that horses can easily tolerate water deprivation that results in a 12% reductions in body mass. The feral horses of the Namib desert were not significantly different per unit mass from domestic horses with regard to indexes of total body water content under conditions of normal hydration and after 72 h of dehydration. Their smaller size and, hence, lower water turnover might be mechanisms they use for survival in the Namib Desert.     

Water balance and osmoregulation in a free-ranging tenebrionid beetle, Onymacris unguicularis, of the Namib Desert

Onymacris unguicularis, a fog-basking tenebrionid beetle of the Namib Desert, has mean water influx rates of 49.9 mg H₂O/g.d and mean efflux rates of 41.3 mg H₂O/g.d with mean mass gain being 10.7 mg/g.d. If only steady-state conditions are considered (no mass change), and passive vapour input subtracted, drinking accounts for 50% of water input. Active beetles must drink in order to maintain water balance, while inactive beetles can maintain water balance either eating seeds or by simply metabolizing fat. Little change is observed in ratios of haemolymph and total body water to dry mass when fogs occur, while significant changes in haemolymph osmotic pressure are associated with fog occurrence.For short periods, O. unguicularis can tolerate dehydration with only slight changes in the ratio of total body water and haemolymph to dry body mass and to haemolymph osmotic pressure. For longer periods however, active beetles must have access to fog water for water balance maintenance. This is probably necessary for reproduction.     

Evidence of a maternal effect that protects against water stress in larvae of the American dog tick, Dermacentor variabilis (Acari: Ixodidae)

We report that the ability to absorb water vapor from the air in larvae of the American dog tick, Dermacentor variabilis, changes depending upon moisture conditions where the eggs develop. When development occurs at lower relative humidities, resultant larvae can replenish water stores, maintain water balance, and survive at relative humidities as low as 75-85% RH, a range that agrees with previously published values for the critical equilibrium humidity or CEH. In contrast, exposure to high relative humidity conditions during development elevates the CEH to 93-97% RH. These larvae can survive only at relative humidities that are close to saturation, as 93% RH is a dehydrating atmosphere. For these larvae, absorption at 97% RH can be prevented by blocking the mouthparts with wax, indicating that an upward shift has occurred in the moisture threshold where the active mechanism for water vapor absorption operates. Based on transfer experiments between low and high relative humidities, the CEH of larvae is determined by the relative humidity experienced by the mother rather than the moisture conditions encountered by eggs after they are laid. The fact that no changes in body water content, dehydration tolerance limit and water loss rate were observed implies that adjustments to the CEH conferred by the mother have the adaptive significance of enabling larvae to maintain water balance by limiting the range of hydrating atmospheres.     

LETTERS TO THE EDITOR

Cox, George W. 1983. Foraging behaviour of the Dune Lark. Ostrich 54:113-120.

Foraging behaviour of the Dune Lark Mirafra erythrochlamys was studied in a dune environment at the Namib Research Institute, Gobabeb, South West Africa/Namibia in August 1981. Birds foraged for a total of 7 h per day in morning and afternoon periods separated by 3 h of inactivity during the warm midday. The birds exploited a distinctive series of vegetational belts dominated by three grasses. About two-thirds of total foraging time was spent in zones of dead and dormant grasses where seeds were sought by excavating small craters in the sand with the bill. Simples taken in the field, and simulations of bill-cratering behaviour in the laboratory, showed that this behaviour displaced seed-poor surface sand and exposed deeper, seed-rich layers. Birds formed small flocks when foraging for seeds in these zones. The remaining third of foraging time was spent in zones with large, live grass clumps, where insects were sought. Insect foraging was concentrated at the start and end of each activity period, but was most intense just before the midday period of inactivity when temperatures approached 30°C. Rough calculations of energy and water balance suggest that the larks are unable to maintain water balance under the observed conditions on seed food alone, and that this balance is achieved by feeding on insects. It is predicted that relative seed and insect foraging effort varies with temperature and season, as also suggested by limited published data on stomach contents in summer and winter.     

Chronic dietary salt stress mitigates hyperkalemia and facilitates chill coma recovery in Drosophila melanogaster

Chill susceptible insects like Drosophila lose the ability to regulate water and ion homeostasis at low temperatures. This loss of hemolymph ion and water balance drives a hyperkalemic state that depolarizes cells, causing cellular injury and death. The ability to maintain ion homeostasis at low temperatures and/or recover ion homeostasis upon rewarming is closely related to insect cold tolerance. We thus hypothesized that changes to organismal ion balance, which can be achieved in Drosophila through dietary salt loading, could alter whole animal cold tolerance phenotypes. We put Drosophila melanogaster in the presence of diets highly enriched in NaCl, KCl, xylitol (an osmotic control) or sucrose (a dietary supplement known to impact cold tolerance) for 24 h and confirmed that they consumed the novel food. Independently of their osmotic effects, NaCl, KCl, and sucrose supplementation all improved the ability of flies to maintain K⁺ balance in the cold, which allowed for faster recovery from chill coma after 6 h at 0 °C. These supplements, however, also slightly increased the CT_min and had little impact on survival rates following chronic cold stress (24 h at 0 °C), suggesting that the effect of diet on cold tolerance depends on the measure of cold tolerance assessed. In contrast to prolonged salt stress, brief feeding (1.5 h) on diets high in salt slowed coma recovery, suggesting that the long-term effects of NaCl and KCl on chilling tolerance result from phenotypic plasticity, induced in response to a salty diet, rather than simply the presence of the diet in the gut lumen.