| surviving the cold: molecular analyses of insect cryoprotective dehydration in the arctic springtail megaphorura arctica (tullberg). | insects provide tractable models for enhancing our understanding of the physiological and cellular processes that enable survival at extreme low temperatures. they possess three main strategies to survive the cold: freeze tolerance, freeze avoidance or cryoprotective dehydration, of which the latter method is exploited by our model species, the arctic springtail megaphorura arctica, formerly onychiurus arcticus (tullberg 1876). the physiological mechanisms underlying cryoprotective dehydration h ... | 2009 | 19622137 |
| compact genome of the antarctic midge is likely an adaptation to an extreme environment. | the midge, belgica antarctica, is the only insect endemic to antarctica, and thus it offers a powerful model for probing responses to extreme temperatures, freeze tolerance, dehydration, osmotic stress, ultraviolet radiation and other forms of environmental stress. here we present the first genome assembly of an extremophile, the first dipteran in the family chironomidae, and the first antarctic eukaryote to be sequenced. at 99 megabases, b. antarctica has the smallest insect genome sequenced th ... | 2014 | 25118180 |
| gene expression changes governing extreme dehydration tolerance in an antarctic insect. | among terrestrial organisms, arthropods are especially susceptible to dehydration, given their small body size and high surface area to volume ratio. this challenge is particularly acute for polar arthropods that face near-constant desiccating conditions, as water is frozen and thus unavailable for much of the year. the molecular mechanisms that govern extreme dehydration tolerance in insects remain largely undefined. in this study, we used rna sequencing to quantify transcriptional mechanisms o ... | 2012 | 23197828 |
| rapid cold-hardening increases the freezing tolerance of the antarctic midge belgica antarctica. | rapid cold-hardening (rch) is well known to increase the tolerance of chilling or cold shock in a diverse array of invertebrate systems at both organismal and cellular levels. here, we report a novel role for rch by showing that rch also increases freezing tolerance in an antarctic midge, belgica antarctica (diptera, chironomidae). the rch response of b. antarctica was investigated under two distinct physiological states: summer acclimatized and cold acclimated. summer-acclimatized larvae were l ... | 2006 | 16424090 |
| osmoregulation and salinity tolerance in the antarctic midge, belgica antarctica: seawater exposure confers enhanced tolerance to freezing and dehydration. | summer storms along the antarctic peninsula can cause microhabitats of the terrestrial midge belgica antarctica to become periodically inundated with seawater from tidal spray. as microhabitats dry, larvae may be exposed to increasing concentrations of seawater. alternatively, as a result of melting snow or following rain, larvae may be immersed in freshwater for extended periods. the present study assessed the tolerance and physiological response of b. antarctica larvae to salinity exposure, an ... | 2009 | 19684222 |
| distinct contractile and cytoskeletal protein patterns in the antarctic midge are elicited by desiccation and rehydration. | desiccation presents a major challenge for the antarctic midge, belgica antarctica. in this study, we use proteomic profiling to evaluate protein changes in the larvae elicited by dehydration and rehydration. larvae were desiccated at 75% relative humidity (rh) for 12 h to achieve a body water loss of 35%, approximately half of the water that can be lost before the larvae succumb to dehydration. to evaluate the rehydration response, larvae were first desiccated, then rehydrated for 6 h at 100% r ... | 2009 | 19415656 |
| the larval alimentary canal of the antarctic insect, belgica antarctica. | on the antarctica continent the wingless midge, belgica antarctica (diptera, chironomidae) occurs further south than any other insect. the digestive tract of the larval stage of belgica that inhabits this extreme environment and feeds in detritus of penguin rookeries has been described for the first time. ingested food passes through a foregut lumen and into a stomodeal valve representing an intussusception of the foregut into the midgut. a sharp discontinuity in microvillar length occurs at an ... | 2009 | 19401239 |
| dehydration, rehydration, and overhydration alter patterns of gene expression in the antarctic midge, belgica antarctica. | we investigated molecular responses elicited by three types of dehydration (fast, slow and cryoprotective), rehydration and overhydration in larvae of the antarctic midge, belgica antarctica. the larvae spend most the year encased in ice but during the austral summer are vulnerable to summer storms, osmotic stress from ocean spray and drying conditions due to wind and intense sunlight. using suppressive subtractive hybridization (ssh), we obtained clones that were potentially responsive to dehyd ... | 2009 | 19125254 |
| high resistance to oxidative damage in the antarctic midge belgica antarctica, and developmentally linked expression of genes encoding superoxide dismutase, catalase and heat shock proteins. | intense ultraviolet radiation, coupled with frequent bouts of freezing-thawing and anoxia, have the potential to generate high levels of oxidative stress in antarctic organisms. in this study, we examined mechanisms used by the antarctic midge, belgica antarctica, to counter oxidative stress. we cloned genes encoding two key antioxidant enzymes, superoxide dismutase (sod) and catalase (cat), and showed that sod mrna was expressed continuously and at very high levels in larvae, but not in adults, ... | 2008 | 18625403 |
| metabolomics reveals unique and shared metabolic changes in response to heat shock, freezing and desiccation in the antarctic midge, belgica antarctica. | the midge, belgica antarctica jacobs, is subjected to numerous environmental stressors during its 2-year life cycle on the antarctic peninsula, and in response it has evolved a suite of behavioral, physiological, and life-cycle modifications to counter these stressors, but thus far only a limited number of biochemical adaptations have been identified. in this study, we use a metabolomics approach to obtain a broad overview of changes in energy metabolism, amino acids, and polyols in response to ... | 2008 | 18313070 |
| cryoprotective dehydration and the resistance to inoculative freezing in the antarctic midge, belgica antarctica. | during winter, larvae of the antarctic midge, belgica antarctica (diptera, chironomidae), must endure 7-8 months of continuous subzero temperatures, encasement in a matrix of soil and ice, and severely desiccating conditions. this environment, along with the fact that larvae possess a high rate of water loss and are extremely tolerant of desiccation, may promote the use of cryoprotective dehydration as a strategy for winter survival. this study investigates the capacity of larvae to resist inocu ... | 2008 | 18245628 |
| 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 ... | 2007 | 17543329 |
| slow dehydration promotes desiccation and freeze tolerance in the antarctic midge belgica antarctica. | adaptations to low moisture availability are arguably as important as cold resistance for polar terrestrial invertebrates, especially because water, in the form of ice, is biologically inaccessible for much of the year. desiccation responses under ecologically realistic soil humidity conditions--those close to the wilting points of plants [98.9% relative humidity (rh)]--have not previously been examined in polar insect species. in the current study we show that, when desiccated at 98.2% rh, larv ... | 2007 | 17297143 |
| continuous up-regulation of heat shock proteins in larvae, but not adults, of a polar insect. | antarctica's terrestrial environment is a challenge to which very few animals have adapted. the largest, free-living animal to inhabit the continent year-round is a flightless midge, belgica antarctica. larval midges survive the lengthy austral winter encased in ice, and when the ice melts in summer, the larvae complete their 2-yr life cycle, and the wingless adults form mating aggregations while subjected to surprisingly high substrate temperatures. here we report a dichotomy in survival strate ... | 2006 | 16968769 |
| rapid cold-hardening in larvae of the antarctic midge belgica antarctica: cellular cold-sensing and a role for calcium. | in many insects, the rapid cold-hardening (rch) response significantly enhances cold tolerance in minutes to hours. larvae of the antarctic midge, belgica antarctica, exhibit a novel form of rch, by which they increase their freezing tolerance. in this study, we examined whether cold-sensing and rch in b. antarctica occur in vitro and whether calcium is required to generate rch. as demonstrated previously, 1 h at -5 degrees c significantly increased organismal freezing tolerance at both -15 degr ... | 2008 | 18417647 |
| dehydration-induced cross tolerance of belgica antarctica larvae to cold and heat is facilitated by trehalose accumulation. | larvae of the antarctic midge, belgica antarctica (diptera: chironomidae), are frequently exposed to dehydrating conditions on the antarctic peninsula. in this study, we examined how rates and levels of dehydration alter heat and cold tolerance and how these relate to levels of trehalose within the insect. when dehydrated, larvae tolerated cold and heat stress more effectively, although resistance to cold was more pronounced than heat resistance. slow dehydration was more effective than rapid de ... | 2009 | 19141330 |
| survival and energetic costs of repeated cold exposure in the antarctic midge, belgica antarctica: a comparison between frozen and supercooled larvae. | in this study, we examined the effects of repeated cold exposure (rce) on the survival, energy content and stress protein expression of larvae of the antarctic midge, belgica antarctica (diptera: chironomidae). additionally, we compared results between larvae that were frozen at -5°c in the presence of water during rce and those that were supercooled at -5°c in a dry environment. although >95% of larvae survived a single 12 h bout of freezing at -5°c, after five cycles of rce survival of frozen ... | 2011 | 21307067 |
| function and immuno-localization of aquaporins in the antarctic midge belgica antarctica. | aquaporin (aqp) water channel proteins play key roles in water movement across cell membranes. extending previous reports of cryoprotective functions in insects, this study examines roles of aqps in response to dehydration, rehydration, and freezing, and their distribution in specific tissues of the antarctic midge, belgica antarctica (diptera, chironomidae). when aqps were blocked using mercuric chloride, tissue dehydration tolerance increased in response to hypertonic challenge, and susceptibi ... | 2011 | 21315725 |
| functional characterization of an aquaporin in the antarctic midge belgica antarctica. | aquaporins (aqps) are water channel proteins facilitating movement of water across the cell membrane. recent insect studies clearly demonstrate that aqps are indispensable for cellular water management under normal conditions as well as under stress conditions including dehydration and cold. in the present study we cloned an aqp cdna from the antarctic midge belgica antarctica (diptera, chironomidae) and investigated water transport activity of the aqp protein and transcriptional regulation of t ... | 2011 | 21497603 |
| energetic consequences of repeated and prolonged dehydration in the antarctic midge, belgica antarctica. | larvae of the antarctic midge, belgica antarctica, routinely face periods of limited water availability in their natural environments on the antarctic peninsula. as a result, b. antarctica is one of the most dehydration-tolerant insects studied, surviving up to 70% loss of its body water. while previous studies have characterized the physiological effects of a single bout of dehydration, in nature larvae are likely to experience multiple bouts of dehydration throughout their lifetime. thus, we e ... | 2012 | 22133311 |
| expression of genes involved in energy mobilization and osmoprotectant synthesis during thermal and dehydration stress in the antarctic midge, belgica antarctica. | the antarctic midge, belgica antarctica, experiences sub-zero temperatures and desiccating conditions for much of the year, and in response to these environmental insults, larvae undergo rapid shifts in metabolism, mobilizing carbohydrate energy reserves to promote synthesis of low-molecular-mass osmoprotectants. in this study, we measured the expression of 11 metabolic genes in response to thermal and dehydration stress. during both heat and cold stress, we observed upregulation of phosphoenolp ... | 2013 | 22972362 |
| autophagy in antarctica: combating dehydration stress in the world's southernmost insect. | the midge belgica antarctica is the only insect endemic to antarctica and has the southernmost range of any insect. in its natural environment, b. antarctica frequently faces desiccating conditions, as environmental water is frozen for up to 9 months annually. the molecular mechanisms by which b. antarctica tolerates extreme dehydration are poorly understood, but recent work from our laboratory reports genome-wide expression changes in response to extreme dehydration (~40% water loss), the first ... | 2013 | 23380735 |
| the protective effect of rapid cold-hardening develops more quickly in frozen versus supercooled larvae of the antarctic midge, belgica antarctica. | during the austral summer, larvae of the terrestrial midge belgica antarctica (diptera: chironomidae) experience highly variable and often unpredictable thermal conditions. in addition to remaining freeze tolerant year-round, larvae are capable of swiftly increasing their cold tolerance through the rapid cold-hardening (rch) response. the present study compared the induction of rch in frozen versus supercooled larvae. at the same induction temperature, rch occurred more rapidly and conferred a g ... | 2013 | 23868837 |
| aquaporins in the antarctic midge, an extremophile that relies on dehydration for cold survival. | the terrestrial midge belgica antarctica relies extensively on dehydration to survive the low temperatures and desiccation stress that prevail in its antarctic habitat. the loss of body water is thus a critical adaptive mechanism employed at the onset of winter to prevent injury from internal ice formation; a rapid mechanism for rehydration is equally essential when summer returns and the larva resumes the brief active phase of its life. this important role for water movement suggests a critical ... | 2015 | 26338869 |
| genome sequencing of the winged midge, parochlus steinenii, from the antarctic peninsula. | in the antarctic, only two species of chironomidae occur naturally-the wingless midge, belgica antarctica , and the winged midge, parochlus steinenii . b. antarctica is an extremophile with unusual adaptations. the larvae of b. antarctica are desiccation- and freeze-tolerant and the adults are wingless. recently, the compact genome of b. antarctica was reported and it is the first antarctic eukaryote to be sequenced. although p. steinenii occurs naturally in the antarctic with b. antarctica , th ... | 2017 | 28327954 |
| surviving in a frozen desert: environmental stress physiology of terrestrial antarctic arthropods. | abiotic stress is one of the primary constraints limiting the range and success of arthropods, and nowhere is this more apparent than antarctica. antarctic arthropods have evolved a suite of adaptations to cope with extremes in temperature and water availability. here, we review the current state of knowledge regarding the environmental physiology of terrestrial arthropods in antarctica. to survive low temperatures, mites and collembola are freeze-intolerant and rely on deep supercooling, in som ... | 2014 | 24353207 |