Lower Supercooling Points Research Articles

The supercooling ability of ticks (Acari, Ixodoidea).

The supercooling capacity of nine laboratory-held species of ticks originating from different geographical areas, as well as five field-collected species from Germany, was investigated. All but one tick species showed mean supercooling points between about -17 and -23 degrees C, suggesting that the capacity to supercool to temperatures of < or = -17 degrees C might be an inherent property of many tick species unrelated to their geographic origin. Photoperiod did not influence the mean supercooling point in any of the species and there was also no distinct seasonal pattern of supercooling in seasonally acclimatized Dermacentor marginatus. Thus, the supercooling ability was independent of the presence/absence of diapause. The finding of thermal hysteresis in D. marginatus hemolymph raises the question of whether or not anti-freeze proteins are involved in the supercooling capacity of that species. An interspecies comparison revealed a weak negative correlation between relative water content and supercooling point of the ticks and an even weaker correlation between body mass or body water mass and the supercooling point. Since the ticks exhibited low supercooling points both before and shortly after feeding, the blood used as food should lack potent ice nucleators.

Developmental patterns of supercooling capacity in a subantarctic wingless fly

Anatalanta aptera is a wingless fly which lives in subantarctic islands, particularly in sea bird colonies. Developmental patterns of supercooling capacity were studied in an experimental population reared at 5°C and fed ad libitum. Mean supercooling points of the eggs, second and third instar larvae, pupae, teneral and mature adults were −28.0°C, −10.8°C, −8.8°C, 17.6°C, −16.6°C and −8.2°C respectively. Low mean supercooling points were found for inactive stages (eggs, pupae) and, unexpectedly among Diptera, teneral adults. Mature adults had a combination of low supercooling ability, high lipid content and physogastry. The results are compared with those obtained in winged species from other families of Diptera.

Low Temperature Effects on Survival of the Eastern Subterranean Termite (Isoptera: Rhinotermitidae)

Reticulitermes flavipes (Kollar) (third and fourth instar) workers from a laboratory colony were subjected to 0°C for either 10 or 30d after having been exposed to 10°C for varied periods from 0 to 30d. Worker mortality increased with increased exposure to 10°C. The lowest percentage of mortality was observed in workers exposed to 0°C for 10d after 0d of 10°C acclimation. Workers exposed to 0°C for 30d exhibited high mortality rates regardless of the duration of the 10°C acclimation periods. The supercooling point of laboratory reared termite workers generally increased with prolonged exposure to 10°C. Termite workers subjected to 0°e for 10d did not exhibit lower supercooling points following increased acclimation periods at 10°. However, termites subjected to 0° for 30d generally did exhibit decreased supercooling points following increased exposure to acclimation temperatures at 10°C. Lower lethal temperatures were higher than the super cooling points for laboratory workers exposed to 10°C for 0, 1, and 10d and for field collected workers during the months of May to July 1992. However, lower lethal temperatures were lower than supercooling points for laboratory termites exposed to 10° for 20 and 30d and for field collected termites during the months of September to November 1992. These data indicate that 10°C cold acclimation of R. flavipes does not result in lower supercooling points in either laboratory maintained or field collected samples. However, decreased lower lethal temperatures in response to either cooler seasonal temperatures or longer exposure does indicate that a switch from prefreeze mortality to freeze tolerance may be occurring.

Insect Cold-Hardiness: Insights from the Arctic

Cold-hardiness and related adaptations of insects in the Arctic correspond to characteristic climatic constraints. Some species are long-lived and are cold-hardy in several stages. In the Arctic, diapause and cold-hardiness are less likely to be linked than in temperate regions, because life-cycle timing depends as much on the need to coincide development with the short summer as on the need to resist winter cold. Winter habitats of many species are exposed rather than sheltered from cold so that development in spring can start earlier. Several features of cold-hardiness in arctic species differ from the characteristics of temperate species: these include very cold-hardy insects with low supercooling points that are not freezing tolerant; freezing-tolerant species that supercool considerably rather than freezing at relatively high subfreezing temperatures; mitochondrial degradation linked with the accumulation of cryoprotectants; and the possibly limited occurrence of thermal hysteresis proteins in winter. Several interesting relationships between cold-hardiness and water have been observed, including different types of dehydration. Winter mortality in arctic insects appear to be relatively low. Adaptations to cold in summer include retention of cold-hardiness, even freezing tolerance; selection of warm sites; and behaviour such as basking that allows elevated body temperatures. Studies especially on the high-arctic moth Gynaephora groenlandica show that various factors including cold-hardiness and other summer and winter constraints dictate the structure of energy budgets and the timing of life cycles. Future work should focus on the biological and climatic differences between arctic and other areas by addressing habitat conditions, life-cycle dynamics, and various aspects of cryoprotectant production at different times of year. Even in the Arctic cold-hardiness is complex and involves many simultaneous adaptations.Key words: cold-hardiness, insects, supercooling, freezing-tolerance, cryoprotectants, metabolism, energy budgets, life cycles, habitat selection

Cold-Hardiness and Supercooling Capacity in Diapausing and Nondiapausing Stages of the Cabbage Root Fly Delia radicum

Supercooling point (SCP) values and cold-hardiness were measured in individual ontogenetic stages of Delia radicum (Diptera:Anthomyiidae) in various physiological states (winter diapause, summer quiescence, and normal development). Winter diapause-destined mature third-instar larvae had a lower SCP (-9.9°C) than their nondiapause counterparts (-5.2°C), and more of them survived exposure to -10°C for 5 h to pupariation and adult emergence. Values of SCPs were equal in both diapause and nondiapause states of prepupal and pupal stages. The lowest SCP (ca. -20°C) was found in the stage of phanerocephalic pupa (PCP) regardless of the physiological state. The cold-hardiness of PCP corresponded with a low SCP value only in diapausing pupae stored for 80 days at 3°C and in pupae which had terminated their diapause and whose further development was inhibited by storage at low temperatures (3°C). Such pupae survived exposure to temperatures close to their SCP (14 days at -17°C). However, this high cold-hardiness was only acquired after some time and/or exposure to 3°C, as the PCP at the beginning of diapause showed significantly impaired cold-hardiness despite the fact that their SCP was low. The cold-hardiness of nondiapausing PCP did not correspond at all to that of low SCP, as no pupa survived the exposure to -17°C for 1 day; survival rates at temperatures of -13.5 and -10°C were also remarkably lower than those in diapausing pupae. Cold-hardiness in D. radicum was closely connected with the diapause syndrome but the changes in SCP value corresponded rather with the ontogeny of this insect.

Cold-hardiness of wolf-spiders (lycosidae, araneae) with particular reference to Pardosa pullata (clerck)

1. 1.Supercooling points of Pardosa pullata, four other lycosids and some Clubionidae, Linyphiidae and Thomisidae were determined. 2. 2.Cold-hardiness was species-specific. P. pullata was the most, and Trochosa ruricola the least, cold-hardy. There was no significant effect of stage or sex. 3. 3.Clubionidae, Linyphiidae and Thomisidae had lower supercooling points than Lycosidae. 4. 4.Mortality in constant conditions depended on both temperature and duration of exposure. 5. 5.Wolf-spiders showed high mortalities at -7°C and below, and could not survive 24h at -9°C.

Cold hardiness of larvae of the southwestern corn borer, Diatraea grandiosella

AbstractThe cold‐hardening capacity of field‐collected larvae from southeast Missouri and laboratory‐reared larvae of the southwestern corn borer, Diatraea grandiosella Dyar, was examined. Supercooling points of non‐diapause and diapause larvae collected from maize plants grown in Missouri (36° 30′ N lat.) were ca. –7.0 °C. The hemolymph melting points of diapause field larvae (–0.8 °C) were significantly lower than those of non‐diapause larvae collected in July (–0.5 °C). The supercooling points of hemolymph from non‐diapause and diapause field larvae ranged randomly from –10° to –18 °C. Supercooling points of non‐diapause laboratory larvae increased from –13° to –10 °C prior to pupation, whereas those of diapause larvae increased similarly before the onset of diapause, but then decreased during diapause to ca. –17 °C. No change in supercooling points or capacity to survive in the presence of ice was observed in diapause laboratory larvae acclimated at 4 °C for 63 days. Laboratory and field larvae began to freeze at ca. –1.5 °C in the presence of ice, but survived to several degrees below their melting points. The high supercooling points of field larvae appeared to be due to the presence of an environmental ice‐nucleator. Although data for laboratory larvae indicate sufficiently low supercooling points to permit winter survival in southeastern Missouri, considerable larval mortality occurs in the field due to inoculative freezing and the presence of an ice‐nucleator.

Regulation of supercooling and nucleation in a freeze intolerant beetle ( Tenebrio molitor)

The mealworm beetle, Tenebrio molitor (Tenebrionidae, Coleoptera), is a freeze-susceptible species that does not survive cooling to below the supercooling point (i.e., tissue freezing) in any stage of development. Most insects of a given age and developmental stage exhibit a relatively narrow range of supercooling point (SCP) values. However, Tenebrio larvae reared at 24 °C on dry wheat bran displayed a wide range of values extending from −1.5 to −24.3 °C. Larvae acclimated at 5 °C had slightly lower SCPs; however, the range of individual values remained highly variable. SCPs were significantly correlated ( r = 0.59) with body weight: small larvae demonstrated a greater capacity for supercooling than larger individuals. In an attempt to identify the specific site of nucleation, the SCPs of hemolymph, fat body, and gut contents were determined and compared to whole body SCPs. Hemolymph and fat body samples generally supercooled to −15 °C or lower for larvae whose whole body SCPs were −5 °C or higher. Only on some occasions could whole body SCPs be explained on the basis of the efficacy of ice nucleators within the gut.

Overwintering strategy of the stem-gall inducer Diplolepis spinosa (Hymenoptera: Cynipidae) in central Ontario

Diplolepis spinosa overwinters as prepupae in large stem galls on rose bushes. The galls are often above the level of the snow, thus exposing the insects within to unabated winter temperatures. Diplolepis spinosa is a freezing-intolerant insect, consistently maintaining its supercooling points below ambient temperatures. It maintained an average supercooling point value of −37.9 ± 5.7 °C between December 29, 1986, and April 8, 1987, at Sudbury, Ontario, during which time the lowest recorded temperature was −31.6 °C. Its low supercooling points were primarily attained by the synthesis and accumulation of glycerol as an antifreeze agent. Glycerol concentrations began rising on October 27, peaked at a concentration of 1032 μmol/g wet weight on December 29 and fell after March 6. The trigger temperature for the initiation of glycerol synthesis was thought to be between 5 and 0 °C. Glycogen accounted for 87% of the glycerol accumulated. A further 3% of the glycerol pool may be accounted for by the contribution of acyl glyceride glycerol liberated by the catabolism of lipid glycerides. It is also suggested that D. spinosa avoids external ice inoculation by consuming all moisture-laden nutritive cells down to the sclerenchyma layer, and avoids internal ice inoculation by defecating before winter.

SUPERCOOLING STUDIES ON THE IMPORTED FIRE ANTS: SOLENOPSIS INVICTA AND SOLENOPSIS RICHTERI (HYMENOPTERA: FORMICIDAE) AND THEIR HYBRID

The discovery of hybrid fire ants, Solenopsis invicta × S. richteri, in northwest Georgia at a more northern latitude than S. invicta led to an investigation into the hybrid's ability to withstand cold temperatures. This study was undertaken to determine if the hybrid would supercool at a lower temperature than either parental species. Major workers, male alates, and female alates of the three ant types were collected, and supercooling points were determined. Of the three castes tested, only male alates of the hybrid and S. richteri had lower supercooling points than did S. invicta. The inhabitance of north Georgia by the hybrid fire ant and not S. invicta does not seem to be determined by supercooling.

Seasonal Changes in Cold Hardiness of Temperate Collembola

The cold hardiness of two temperate collembolan species Orchesella cincta L. and Tomocerus minor (Lubbock) was compared. The supercooling points of the two show a bimodal distribution over the year with a group of high and of low values. Both groups show a distinct seasonal change. Adults and juveniles differ only slightly. 0. cincta has lower supercooling points than T. minor. This is in accordance with the fact that the former species lives more exposed than the latter. Frost induces gut evacuation in 0. cincta, which is considered a cold hardiness mechanism. Measurements on both ionized and the total osmotic fraction reveal that changes of the osmotic value of the haemolymph during winter are not caused by release of osmotically active cryoprotectants but by dehydration.

Extreme Supercooling as an Overwintering Strategy in Three Species of Willow Gall Insects from Interior Alaska

(1) Seasonal cold-hardiness was studied in insect larvae associated with three different types of willow galls. (2) Mean supercooling points in summer were unusually low, ranging from -25.5°C to -29.4°C. Winter supercooling points were the lowest that have been recorded for any insects and ranged from -56°C to -58°C, with a number of individuals of each larval species exhibiting supercooling points of -61° to -64°C. (3) Low supercooling points in winter were associated with accumulation of glycerol averaging between 4 and 6 molal in the three species. Melting points of body fluids were greatly depressed and averaged -14° and -18°C in two species. (4) None of the willow gall larvae were freezing-tolerant, and all relied on freezing avoidance by extreme supercooling in order to survive low winter habitat temperatures. (5) Injection of winter larvae with efficient ice-nucleators raised the supercooling point approximately 25°C but did not confer freezing-tolerance.

Cold-Hardiness in the Antarctic Tick, Ixodes uriae

Ixodes uriae White (Ixodidae, Acarina) is the predominant tick on the Antarctic peninsula. This species has a circumpolar distribution in both hemispheres and is associated with or known to parasitize 48 species of seabirds. Large colonies of 1,000 or more individuals of all life stages were found beneath rocks on the periphery of Adelie penguin rookeries near Palmer Station, Anvers Island. All life stages (egg, larva, nymph, and adult) were intolerant of freezing. Engorged nymphs and larvae had supercooling points between -18 and -20 C. Eggs had the lowest supercooling points (-28.7 C), while adults had the highest values (from -7 to -13 C). Acclimation to temperatures between -12 and +25 C for 2 wk had no effect on the supercooling point of engorged immobile nymphs. Desiccation of engorged nymphs to 80% of their initial weight resulted in no change in supercooling points or glycerol levels. In January, engorged nymphs enter a state of apolysis and lose mobility. Correlated with this change is an increas...

Effects of ingestion of liquids on the cold tolerance of an Antarctic mite

Samples of a cryptostigmatid mite, Alaskozetes antarcticus, were collected during summer and winter on Signy Island, South Orkney Islands, in the maritime Antarctic. In four experiments, adult mites were maintained at 4°C and 100% r.h. for periods of 14, 28 and 32 days. In two of these experiments the mites received cold-hardening pre-treatments at −15 and −20°C (56 and 21 days respectively). The experiments compared: (1) The effects of acclimation with and without access to distilled water, (2) the effects of liquid glucose (10% solution) and algal diets, in terms of cold hardiness (supercooling points and cryoprotectant levels). In one of the experiments, changes in live weight and body water content were determined. For cold-hardy mites, with high glycerol levels and low supercooling points, the distilled water and glucose treatments produced an extreme loss (about 20–25°C) of supercooling ability. When no liquid was available, only a small (about 4°C) loss occurred. Glycerol concentrations decayed in both cases. Non cold-hardy mites, with low glycerol levels and a wide range of supercooling points, did not show differing responses when acclimated at 4°C with and without distilled water, but exposure to glucose solution did result in extreme supercooling point elevations. These results are related to seasonal changes in Alaskozetes cold hardiness in the field, and are discussed in terms of hypotheses advocating external (bacterial and mineral) and internal (organic) sources of ice-nucleating agents.

Cold tolerance in diapausing and non‐diapausing stages of the flesh fly, Sarcophaga crassipalpis

ABSTRACT. Supercooling points (SCP) and low temperature tolerance were determined for larval, pupal and adult stages of Sarcophaga crassipalpis Macquart (Diptera: Sarcophagidae). No stage tolerates tissue‐freezing. Ontogenetic changes in SCP profiles are similar for comparable developmental stages of diapause and non‐diapause groups. Feeding larvae have SCPs near ‐7°C which decrease to ‐11°C in the postfeeding wandering phase of the final larval instar. The lowest SCPs are recorded for pupae at ‐23°C. The capacity to survive at ‐17°C varies with age of the diapausing pupae: 10‐day‐old pupae are less cold tolerant than pupae that have been in diapause for 45–80 days. Although the SCP of non‐diapausing pupae is as low as in diapausing pupae, non‐diapausing pupae are extremely sensitive to low temperature exposure and do not survive to adult eclosion when exposed to ‐17°C for as little as 20 min. The use of hexane to break pupal diapause has no effect on SCPs or low temperature tolerance.

Cold Hardiness and Overwintering Survival of the Sugarbeet Root Maggot (Diptera: Otitidae) in Southern Alberta

Mature third instar larvae of the sugarbeet root maggot, Tetanops myopaeformis (Roder), were exposed to constant temperatures of −15, −10, −5, 0.5, 2.5, and 5°C for 6 months. Larval survival and pupation were greatest at 5°C and significantly less survival was observed at temperatures below 0.5°C. Supercooling point determination indicated that although larvae can supercool to −11°C, mortality may occur at temperatures above the supercooling point, especially under extended periods (6 months) of low temperatures. There were significant differences in the vertical distribution of larvae in the soil; the majority of larvae were observed to occur at a depth of 10–20 cm in September, 5–15 cm in January and February, and 0–15 cm in April. Survival and pupation of larvae averaged 87.1 and 74.1%, respectively, and there were no significant differences in larval survival at soil depths of 5–30 cm. High overwintering survival of the larvae is attributed to their low supercooling points, freezing tolerance, and the ability of larvae to move within the soil to take advantage of the thermal damping properties of soil throughout the season.

Seasonal changes of glycogen/trehalose contents, supercooling points and survival rate in mature larvae of the overwintering soybean pod borer Leguminivora glycinivorella

The mature larvae of the soybean pod borer Leguminivora glycinivorella, spend over 9 months (October-next August) in the inactive state until pupation down to 3 cm below the surface in soil. Trehalose content of inactive larvae increases in early winter, attaining a maximum (ca 30 mg/g), and decreases in spring, with a concomitant decrease and increase of glycogen. The median supercooling points seasonally change from −19.8°C (October) to −25.0°C (February), and to −17.0°C (June). The lower supercooling points in winter are in part due to the absence of unusually high values (> −18°C). The increase in trehalose does not seem to be effective in depressing the supercooling points. The larvae are freeze-intolerant, but ambient temperatures in outdoor conditions are always above the supercooling points. The survival rates are very high throughout the inactive period.

Supercooling points of insects and mites on the Antarctic Peninsula

Abstract. 1. Mean supercooling points of eleven species of arthropods (three Collembola, seven Acari and one Diptera) ranged from ‐6.2 to ‐9.4°C (high group), and from ‐17.7 to ‐31.0°C (low group). The majority of individuals in the high group had food in their gut systems.2. Freezing was lethal to all species examined except larval Belgica antarctica Jacobs (Chironomidae).3. Glucose, glycerol and mannitol were found in low concentrations in extracts of Ctyptopygus antarcticus Willem (Collembola) and larvae of B. antarcrica; it is udikely that these substances had a major effect on the supercooling of either species.4. Two Collembola species possessed significantly (P&lt; 0.05) lower supercooling points at locations on the Antarctic Pensinsula than at Signy Island, South Orkney Islands. The converse was observed for two species of Acari.5. It is suggested that whilst gross climatic and also micro‐habitat conditions may influence the cold hardiness of such arthropods, especially seasonally, their full supercooling ability is rarely tested.

Freezing-tolerant insects with low supercooling points

1. 1. Pytho deplanatus [Coleoptera: Pythidae (Salpingidae)] is an alpine species that overwinters as a larva under the bark of fallen spruce in the Rocky Mountains. It belongs to a small group of insects which not only is tolerant of freezing but also develops the capacity to supercool to low sub-zero temperatures (−54°C), indeed in this case the lowest ever recorded for this category. 2. 2. The freezing tolerance profile of P. deplunatus is similar to that of many other insects in that glycerol is accumulated to moderately high levels during low temperature acclimation, while water content and glycogen concentrations are considerably reduced. Blood sugar levels, mainly trehalose. also accumulate during this period. 3. 3. The most feasible explanation for the co-existence of freezing tolerance and low supercooling points is that P. deplanatus is physiologically incapable of synthesizing haemolymph nucleating agents and that nucleators in the gut and other fluid compartments are absent in the overwintering larvae. The adaptive advantage of this strategy is that larvae would normally overwinter in a supercooled state, but if freezing did occur (e.g. by inoculation from contact water in the hibernaculum) then the antifreeze function of glycerol and blood sugars would assume a cryoprotective role. 4. 4. The freezing tolerance mechanisms of P. deplanatus larvae are compared and contrasted with those of (a) the congeneric P. americanus which also overwinters under the bark of fallen trees but has both an alpine and arctic distribution, and (b) Xylophagus sp. (Diptera: Xylophagidae) which has a different phylogenetic background but occupies a similar niche in the Arctic.

Cold-hardiness strategies of some adult and immature insects overwintering in interior Alaska

1. 1. A variety of adult and immature insects, most of which occupy highly exposed habitats. successfully overwinter in interior Alaska. 2. 2. A number of adult beetles are freezing-tolerant. All exhibit relatively high supercooling points and synthesize large quantities of polyhydric alcohols in response to cold. 3. 3. At least four other orders are represented by adult insects that tolerate freezing, but in contrast to adult beetles, all exhibit relatively low supercooling points associated with the build-up of glycerol. 4. 4. At least three species of larvae that overwinter in galls undergo a remarkable increase in supercooling capability (to ca. −60°C) associated with synthesis of large quantities of glycerol in winter. 5. 5. None of the larvae tested could survive freezing in spite of their high glycerol levels.