Temperature selection and critical thermal maxima of the fantail darter,Etheostoma flabellare,and johnny darter,E. nigrum,related to habitat and season

Synopsis Riffle dwelling fantail darters (Etheostoma flabellare) selected lower temperatures in winter (19.3°C) compared to pool dwelling johnny darters (E. nigrum; 22.0°C. A similar trend was evident in summer tests (fantail darters, 20.3°C; johnny darters, 22.9°C). Summer tested animals selected higher temperatures than winter tested animals maintained at the same acclimation temperature and photoperiod. When tested together in the same gradient, both species appeared not to thermoregulate, but tended to avoid each other. Critical thermal maxima (CTMax) did not differ between seasons for either species (fantail darters, 31.1°C winter, 31.3°C summer; johnny darters, 30.9°C winter, 30.5°C summer). Differences in the thermal responses of these darters correlated with differences in their respective habitats.     

Thermal maxima for juvenile shortnose sturgeon acclimated to different temperatures

Many populations of shortnose sturgeon, Acipenser brevirostrum, in the southeastern United States continue to suffer from poor juvenile recruitment. High summer water temperatures, which may be exacerbated by anthropogenic activities, are thought to affect recruitment by limiting available summer habitat. However, information regarding temperature thresholds of shortnose sturgeon is limited. In this study, the thermal maximum method and a heating rate of 0.1°C min⁻¹ was used to determine critical and lethal thermal maxima for young-of-the-year (YOY) shortnose sturgeon acclimated to temperatures of 19.5 and 24.1°C. Fish used in the experiment were 0.6 to 35.0 g in weight and 64 to 140 days post hatch (dph) in age. Critical thermal maxima were 33.7°C (±0.3) and 35.1°C (±0.2) for fish acclimated to 19.5 and 24.1°C, respectively. Critical thermal maxima significantly increased with an increase in acclimation temperature (p < 0.0001). Lethal thermal maxima were 34.8°C (±0.1) and 36.1°C (±0.1) for fish acclimated to 19.5 and 24.1°C, respectively. Lethal thermal maxima were significantly affected by acclimation temperature, the log₁₀ (fish weight), and the interaction between log₁₀(fish weight) and acclimation temperature (p < 0.0001). Thermal maxima were used to estimate upper limits of safe temperature, thermal preferences, and optimal growth temperatures of YOY shortnose sturgeon. Upper limits of safe temperature were similar to previous temperature tolerance information and indicate that summer temperatures in southeastern rivers may be lethal to YOY shortnose sturgeon if suitable thermal refuge cannot be found.     

The influence of thermal history on upper thermal limits of two species of riverine insects: the stonefly, <Emphasis Type="Italic">Aphanicerca capensis</Emphasis>, and the mayfly, <Emphasis Type="Italic">Lestagella penicillata</Emphasis>

The upper thermal limits of two cold-water stenotherms: the mayfly, Lestagella penicillata (Teloganodidae), and the stonefly, Aphanicerca capensis (Notonemouridae), were determined from six rivers in the Western Cape, South Africa. Limits were estimated using the Critical Thermal Method (expressed as Critical Thermal maximum) and the Incipient Lethal Temperature method (expressed as Incipient Lethal Upper Limit). Hourly water temperatures recorded in these rivers were used to characterise thermal signatures. Median CT_max and 96 h ILUT varied significantly amongst rivers for both species (≤5.7°C for CT_max and ≤4.0°C for 96 h ILUT) and variation was similar for both species. Differences in water temperature amongst rivers during the experimental period (spring) were insufficient (<2.0°C) to confirm the relationship between upper thermal limits and thermal history, expressed as an averaging statistic derived from in situ water temperatures. Greatest thermal range was over the warm summer period (>8.0°C) and it is likely that this is when thermal history may influence thermal limits. Maximum Weekly Allowable Temperature thresholds averaged for all rivers were lower for A. capensis (17.0°C) compared to L. penicillata (19.0°C). Both species have life cycles that allow them to avoid the thermally stressful summer period.     

Thermal ecology of allopatric lizards (Sphenomorphus) in southeast Australia

Summary The Sphenomorphus quoyi species complex (Lacertilia: Scincidae) of southeast Australia consists of three lizard species, distributed as continuous but largely allopatric populations, and a fourth species which has a disjunct distribution at high altitudes within the range of the other three. The four species have similar Voluntary temperatures (range of body temperatures within which normal activity occurs) despite the fact that they occupy different geographical areas.Altitudinal zonation is shown in the distribution pattern of the four species with S. quoyi and S. tympanum (warm temperate) restricted to the lower altitudes. The level of the mean daily minimum and maximum temperatures are different in each of the four species distribution areas. Similarly, the area occupied by each species is characterized by different daily sunlit and shade surface temperatures and different duration of ground surface subzero temperatures. Floristic composition of the four areas and the basking sites utilized by each species are also dissimilar.The lower temperature tolerances and the acclimation range of the Critical Minimum temperatures of S. quoyi and S. tympanum (warm temperate) exclude these species from the higher altitudes with the relatively lower environmental temperature levels. The Critical temperatures of the species which are found at high altitudes, do not explain why sympatry is not found with the lowland species.     

Thermal tolerance of Litopenaeus vannamei (Crustacea: Penaeidae) acclimated to four temperatures

Critical thermal minima (CTMin) and maxima (CTMax) values were determined for the Pacific white shrimp Litopenaeus vannamei post-larvae and juveniles at four different acclimation temperatures (15, 20, 25, and 30 °C). The CTMin of shrimp at these acclimation temperatures were 7.82, 8.95, 9.80, and 10.96 °C for post-larvae and 7.50, 8.20, 10.20, and 10.80 °C for juveniles, respectively, at 1 °C h⁻¹ cooling rate. The CTMax values were 35.65, 38.13, 39.91, and 42.00 °C for post-larvae and 35.94, 38.65, 40.30, and 42.20 °C for juveniles at the respective acclimation temperatures. Both acclimation temperature and size of the shrimp affected CTMin values of L. vannamei (P<0.01). Overall, juveniles displayed significantly lower CTMin values than the post-larvae (P<0.0001). However, the CTMax response by post-larvae and juveniles were not significantly different from each other and no interaction was determined between the acclimation temperature and development stage (P>0.01). The area of the thermal tolerance polygon over four acclimation temperatures (15, 20, 25, and 30 °C) for the post-larvae of L. vannamei was calculated to be 434.94 °C². The acclimation response ratio (ARR) values were high ranging from 0.35 to 0.44 for both post-larvae and juveniles. L. vannamei appears to be more sensitive to low temperatures than other penaeid species and its cold tolerance zone ranged from 7.5 to 11 °C. In successful aquaculture temperature must never fall below 12 °C to prevent mortalities. Upper thermal tolerance is less of a problem as in most subtropical regions maximum water temperature rarely exceeds 34 °C, but care should be given if shallow ponds with low water renewal rate are being used.     

Capillarisation,oxygen diffusion distances and mitochondrial content of carp muscles following acclimation to summer and winter temperatures

Summary Many species of fish show a partial or complete thermal compensation of metabolic rate on acclimation from summer to winter temperatures. In the present study Crucian carp (Carassius carassius L.) were acclimated for two months to either 2° C or 28° C and the effects of temperature acclimation on mitochondrial content and capillary supply to myotomal muscles determined.Mitochondria occupy 31.4% and 14.7% of slow fibre volume in 2°C- and 28° C-acclimated fish, respectively. Fast muscles of coldbut not warm-acclimated fish show a marked heterogeneity in mitochondrial volume. For example, only 5 % of fast fibres in 28° C-acclimated fish contain 5 % mitochondria compared to 34 % in 2° C-acclimated fish. The mean mitochondrial volume in fast fibres is 6.1 % and 1.6 % for coldand warm-acclimated fish, respectively.Increases in the mitochondrial compartment with cold acclimation were accompanied by an increase in the capillary supply to both fast (1.4 to 2.9 capillaries/fibre) and slow (2.2 to 4.8 capillaries/fibre) muscles. The percentage of slow fibre surface vascularised is 13.6 in 28° C-acclimated fish and 32.1 in 2° C-acclimated fish. Corresponding values for fast muscle are 2.3 and 6.6 % for warm and cold-acclimated fish, respectively. Maximum hypothetical diffusion distances are reduced by approximately 23–30 % in the muscles of 2° C-compared to 28° C-acclimated fish. However, the capillary surface supplying 1 ³ of mitochondria is similar at both temperatures.Factors regulating thermal compensation of aerobic metabolism and the plasticity of fish muscle to environmental change are briefly discussed.     

Habitat temperature and potential locomotor activity of the continental Antarctic mite,Maudheimia petronia Wallwork (Acari: Oribatei)

Microhabitat recordings suggest that the continental Antarctic mite Maudheimia petronia Wall-work experiences temperatures above 0°C for 60% of the time during summer (about 2 months). Summer daily maximum temperatures are, however, often relatively high (the highest recorded temperature was 27.7°C). Because the locomotor activity of this mite is suppressed at freezing temperatures, the time available for activity, and probably also feeding, is restricted. Temperature relations of potential locomotor activity rate suggest alleviation of this time constraint through the maximization of the rate. The locomotor activity rate of M. petronia is positively sensitive to the entire range of above-zero temperatures that it naturally experiences, being particularly accelerated at lower temperatures (Q_100°–5°C values were above 13, whereas Q_{1025°–30°C} values were below 2). Also, comparisons between mites acclimated at -15°C and 10°C suggest an inverse temperature acclimation of this rate. We hypothesize that potential feeding rate is similarly related to temperature. A relative enhancement of food intake would seem important, not only for the maintenance of a daily positive energy balance in summer, but also for the building up of energy reserves for the relatively long winter, when feeding is impossible.     

A note on the upper lethal temperature of juvenile Haemulon flavolineatum from the Virgin Islands

Lethal temperature relations of a sample of juvenile French grunts, Haemulon flavolineatum (Desmarest), were studied. The Critical Thermal Maximum (CTM) and resistance times at four elevated temperatures were determined. Exposure time is considered to be of prime importance in studies of thermal tolerance.     

Thermopreference,tolerance and metabolic rate of early stages juvenile Octopus maya acclimated to different temperatures

Thermopreference, tolerance and oxygen consumption rates of early juveniles Octopus maya (O. maya; weight range 0.38–0.78 g) were determined after acclimating the octopuses to temperatures (18, 22, 26, and 30 °C) for 20 days. The results indicated a direct relationship between preferred temperature (PT) and acclimated temperature, the PT was 23.4 °C. Critical Thermal Maxima, (CTMax; 31.8±1.2, 32.7±0.9, 34.8±1.4 and 36.5±1.0) and Critical Thermal Minima, (CTMin; 11.6±0.2, 12.8±0.6, 13.7±1.0, 19.00±0.9) increased significantly (P<0.05) with increasing acclimation temperatures. The endpoint for CTMax was ink release and for CTMin was tentacles curled, respectively. A thermal tolerance polygon over the range of 18–30 °C resulted in a calculated area of 210.0 °C². The oxygen consumption rate increased significantly α=0.05 with increasing acclimation temperatures between 18 and 30 °C. Maximum and minimum temperature quotients (Q₁₀) were observed between 26–30 °C and 22–26 °C as 3.03 and 1.71, respectively. These results suggest that O. maya has an increased capability for adapting to moderate temperatures, and suggest increased culture potential in subtropical regions southeast of México.     

Exogenous Abscisic Acid Mimics Cold Acclimation for Cacti Differing in Freezing Tolerance

The responses to low temperature were determined for two species of cacti sensitive to freezing, Ferocactus viridescens and Opuntia ficus-indica, and a cold hardy species, Opuntia fragilis. Fourteen days after shifting the plants from day/night air temperatures of 30/20[deg]C to 10/0[deg]C, the chlorenchyma water content decreased only for O. fragilis. This temperature shift caused the freezing tolerance (measured by vital stain uptake) of chlorenchyma cells to be enhanced only by about 2.0[deg]C for F. viridescens and O. ficus-indica but by 14.6[deg]C for O. fragilis. Also, maintenance of high water content by injection of water into plants at 10/0[deg]C reversed the acclimation. The endogenous abscisic acid (ABA) concentration was below 0.4 pmol g-1 fresh weight at 30/20[deg]C, but after 14 d at 10/0[deg]C it increased to 84 pmol g-1 fresh weight for O. ficus-indica and to 49 pmol g-1 fresh weight for O. fragilis. Four days after plants were sprayed with 7.5 x 10-5 M ABA at 30/20[deg]C, freezing tolerance was enhanced by 0.5[deg]C for F. viridescens, 4.1[deg]C for O. ficus-indica, and 23.4[deg]C for O. fragilis. Moreover, the time course for the change in freezing tolerance over 14 d was similar for plants shifted to low temperatures as for plants treated with exogenous ABA at moderate temperatures. Decreases in plant water content and increases in ABA concentration may be important for low-temperature acclimation by cacti, especially O. fragilis, which is widely distributed in Canada and the United States.     

Some effects of giant Andean stem-rosettes on ground microclimate,and their ecological significance

The effect of giant Andean stem-rosettes (Coespeletia lutescens) on air and soil temperatures was studied in the Páramo de Piedras Blancas (Venezuela) at 4265 and 4385 m altitude during the dry season, which is the coldest season in this tropical mountain area. Maximum air temperatures beneath a plant canopy were only slightly higher than in the open. Minimum temperatures below the stem-rosettes were 4.7° to 7.0°C higher than in the open. This substantially reduced the intensity of nightly freezing. Soil temperature minima at 20 cm depth were 2.4° to 4.2°C higher below plants, but maxima were somewhat lower than in bare soil. These microclimatic alterations are ecologically significant for stemprosette seedlings, which should have a higher probability of survival due to the reduced frequency of frost and needle ice formation below large plants. Warmer soils at night should also result in greater water uptake by seedlings during the early morning hours, thus reducing dry-season mortality.     

Upper-lethal-temperature relations of the nymphs of the stonefly,paragnetina media

Summary Continuous water flow and static test apparatus were used in evaluating the influence of acclimation temperature, size, sex, season, life stage, current velocity, and testing method upon the upper-lethal temperature of the nymphal stage of the stonefly, Paragnetina media Walker.Lethal temperature was raised by acclimation to higher temperatures throughout the thermal range examined. The rate of gain of heat resistance was approximately 5°C per day. Acclimation to colder temperatures was much slower.Body size had no significant effect on upper-lethal temperature in summer or autumn, whereas in winter and spring larger nymphs were significantly less tolerant than smaller nymphs. This difference was attributed to sex, not body size per se.Tolerance was significantly less in static waters than in flowing water, faster current significantly increasing heat resistance at all lethal temperatures examined.Upper-lethal temperatures showed seasonal differences independent of acclimation, with nymphs least tolerant in spring, when temperature resistance was influenced by sex, molting condition, and proximity of emergence. The most temperature-sensitive stage was the period immediately following egg hatching.The direct effect of upper-lethal temperature is apparently not a limiting factor for P. media in the environment in which it is found. Temperature increases do, however, effect final stages of nymphal development, emergence patterns, and survival after hatching.Contribution No. 213, W. K. Kellogg Biological Station of Michigan State University. This investigation was supported in part by Research Grant WP 01178 from the Federal Water Pollution Control Administration.     

Seasonal variation in the physical properties of agar and biomass of Gracilaria sp. (chorda type) from Tosa Bay,southern Japan

Plants of Gracilaria sp.(chorda type), which grow along the coast of Uranouchi Inlet in Tosa Bay, southern Japan, showed the highest biomass in the summer (26 °C to 31 °C) and spring season (15.1 °C to 24.9 °C). Maximum biomass was 6952 g m^–2 in July, but gradually decreased in the autumn (30.5 °C in September to 20 °C in November) and winter (19.5 °C in December to 14.9 °C in February). Variation in yields and gel strength of the agars, were shown to depend on the time in the season. After alkali treatment (5% NaOH, 2 h) at three different temperatures (70, 80, and 90 °C), the agars showed gel strengths essentially that of commercial grade agars, with the best gel obtained at 80 °C. Maximum gel strength (1455 g cm^–2 of 1.5% agar gel) occurred in winter when the biomass and agar yield were low. Minimum gel strength was in spring. Gel strength was inversely correlated with agar yield, but was positively correlated with apparent viscosity. Maximum viscosity was 40 cP. in December. Gelling temperatures, pH of 1.5% agar gel, and moisture content in agars showed little variation.     

Temperature responses of growth and photosynthetic CO2 exchange rates in coastal and desert races of Atriplex lentiformis

Summary Comparative measurements of CO₂ exchange and growth rates were made on Atriplex lentiformis (Torr.) Wats. plants from populations native to coastal as well as desert habitats in southern California. While both had similar CO₂ exchange rates at moderate growth temperatures, the desert plants had a substantially greater capacity to acclimate to high growth temperatures indicating that clear ecotypic differences in acclimation capacity are present in this species. This large capacity for photosynthetic acclimation resulted in nearly equal CO₂ exchange rates of the desert plants under the different day temperatures characteristic of the desert habitat during the summer and winter months. In contrast, the photosynthetic CO₂ exchange rates of the coastal plants was markedly reduced by high growth temperatures. The large acclimation capacity of the desert plants may function to maintain high productivities during both the winter and summer months but would not be required in the coastal plants because of the moderate temperatures throughout the year in their native habitat.Relative growth rates (RGR) of the coastal and desert plants were similar at 23°C day/18°C night and 33°C day/25°C night growth temperatures. At 43°C day/30°C night temperatures, however, the RGR of the desert plants was higher than that of the coastal plants. Thus, the larger acclimation capacity of the desert plants is related to a greater ability to maintain high growth rates over a wide range of temperatures as compared to the coastal plants. Small differences in allocation patterns could account for differences in the comparative photosynthetic responses and growth rates in each temperature regime.Supported by National Science Foundation grant # GB 36311     

Thermal tolerance of European Sea Bass (Dicentrarchus labrax) juveniles acclimated to three temperature levels

This study was carried out to determine upper (CTMax) and lower (CTMin) thermal tolerance, acclimation response ratio (ARR) and thermal tolerance polygon of the European sea bass inhabiting the Iskenderun Bay, the most southeasterly part of the Mediterranean Sea, at three acclimation temperatures (15, 20, 25 °C). Acclimation temperature significantly affected the CTMin and CTMax values of the fish. At 0.3 °C min⁻¹ cooling or heating rate, CTMin ranged from 4.10 to 6.77 °C and CTMax ranged from 33.23 to 35.95 °C in three acclimation temperatures from 15 to 25 °C. Thermal tolerance polygon for the juveniles at the tested acclimation temperatures was calculated to be 296.14 °C². In general, the current data show that our sea bass population possesses acclimation response ratio (ARR) values (0.25-0.27) similar to some tropical species. The cold tolerance values attained for this species ranged from 4.10 to 6.77 °C, suggesting that cold winter temperatures may not pose danger during the culture of European sea bass in deep ponds or high water exchange rate systems. Upper thermal tolerance is more of a problem in the southern part of the Mediterranean as maximum water temperature in ponds may sometimes exceed 33-34 °C, during which underground cool-water should be used to lower ambient water temperature in the mid-summer. For successful culture of sea bass in ponds, temperature should be maintained around 25 °C throughout the year and this can be managed under greenhousing systems using underground well-waters, commonly available in the region.     

Thermal preference,tolerance and oxygen consumption of adult white shrimp Litopenaeus vannamei (Boone) exposed to different acclimation temperatures

Final temperature preferendum of white shrimp adults were determined with acute and gravitation methods. The final preferendum was similar, independent of method (26.2–25.6 °C). A direct relationship was determined between the critical thermal maxima values and the acclimation temperatures (P<0.05). The end point of Critical Thermal Maxima (CTMax) for adults was defined as the loss of righting response (LRR). The acclimation response ratio (ARR) for adults of white shrimp had an interval of 0.36–0.76, values that agreed with others obtained for crustaceans from tropical and subtropical climates. The oxygen consumption rates increased significantly (P<0.05) from 39.6 up to 90.0 mg O₂ kg⁻¹ h⁻¹ wet weight (w.w.) as the acclimation temperature increased from 20 to 32 °C. The range of temperature coefficient (Q₁₀) of the white shrimp between 23 and 26 °C was the lower 1.60. The results obtained in this work are discussed in relation to the species importance in the reproductive scope and maintenance of breeders.     

Differential responses of thermal tolerance to acclimation in the sub-Antarctic rove beetle Halmaeusa atriceps

Abstract. Investigations of the responses to acclimation of upper and lower lethal limits and limits to activity in insects have focused primarily on Drosophila. In the present study, Halmaeusa atriceps (Staphylinidae) is examined for thermal tolerance responses to acclimation, and seasonal acclimatization. In summer and winter, lower lethal temperatures of adults and larvae are approximately −7.6 ± 0.03 and −11.1 ± 0.06 °C, respectively. Supercooling points (SCPs) are more variable, with winter SCPs of −5.4 ± 0.4 °C in larvae and −6.3 ± 0.8 °C in adults. The species appears to be chill susceptible in summer and moderately freeze tolerant in winter, thus showing seasonal acclimatization. Similar changes cannot be induced solely by acclimation to low temperatures in the laboratory. Upper lethal temperatures show a weaker response to acclimation. There are also significant responses to acclimation of critical thermal limits. Critical thermal minima vary between −3.6 ± 0.2 and −0.6 ± 0.2 °C in larvae, and from −4.1 ± 0.1 to −0.8 ± 0.2 °C in adults. By contrast, critical thermal maxima vary much less within adults and larvae. These findings are in keeping with the general pattern found in insects, although this species differs in several respects from others found on Marion Island.     

Seasonal modulation of plasma antifreeze protein levels in Atlantic (Anarhichas lupus) and spotted wolffish (A. minor)

The Atlantic and spotted wolffish (Anarhichas lupus and A. minor, respectively) inhabit the cold waters of the northeast Atlantic Ocean. Although both species experience subzero water temperatures during winter, the Atlantic wolffish, which occupies shallower waters than the spotted wolffish, faces the greater threat of coming into contact with ice and freezing. This laboratory study was designed to determine whether these species differed in their abilities to resist freezing by examining the seasonal changes in blood plasma freezing points, antifreeze protein (AFP) activity and Na⁺ and Cl⁻ concentrations when exposed to seasonally cycling water temperatures and photoperiod. The plasma of both species showed distinct seasonal cycles in all parameters with the highest values occurring during the winter. However, of the two species, only the Atlantic wolffish produced sufficient AFP to protect the fish down to the freezing point of seawater (− 1.80 °C). The levels of AFP in the spotted wolffish were too low to impart any significant improvement in their resistance to freezing (approximately − 0.8 °C).When wolffish were maintained in warm water under a seasonally changing photoperiod, the amplitude of the seasonal cycle in AFP activity was greatly reduced, indicating that low water temperatures are necessary to maximize plasma AFP levels. However, despite being maintained in warm water, plasma levels of AFP activity began to increase over summer values at the same time of year as did the fish exposed to seasonally changing water temperatures. This suggests that photoperiod plays a major role in the timing of the annual AFP cycle.     

Freezing survival, body ice content and blood composition of the freeze-tolerant European common lizard, Lacerta vivipara

To investigate the freeze tolerance of the European common lizard, Lacerta vivipara, we froze 17 individuals to body temperatures as low as -4 degrees C under controlled laboratory conditions. The data show that this species tolerates the freezing of 50% of total body water and can survive freezing exposures of at least 24-h duration. Currently, this represents the best known development of freeze tolerance among squamate reptiles. Freezing stimulated a significant increase in blood glucose levels (16.15+/- 1.73 micromol x ml(-1) for controls versus 25.06 +/- 2.92 micromol x ml(-1) after thawing) but this increase had no significant effect on serum osmolality which was unchanged between control and freeze-exposed lizards (506.0 +/- 23.8 mosmol x l(-1) versus 501.0 +/- 25.3 mosmol x l(-1), respectively). Tests that assessed the possible presence of antifreeze proteins in lizard blood were negative. Recovery at 5 degrees C after freezing was assessed by measurements of the mean time for the return of breathing (5.9 +/- 0.5 h) and of the righting reflex (44.8 +/- 4.5 h). Because this species hibernates in wet substrates inoculative freezing may frequently occur in nature and the substantial freeze tolerance of this lizard should play a key role in its winter survival.