Increasing ocean temperatures reduce activity patterns of a large commercially important coral reef fish

Large‐bodied fish are critical for sustaining coral reef fisheries, but little is known about the vulnerability of these fish to global warming. This study examined the effects of elevated temperatures on the movement and activity patterns of the common coral trout Plectropomus leopardus (Serranidae), which is an important fishery species in tropical Australia and throughout the Indo West‐Pacific. Adult fish were collected from two locations on Australia's Great Barrier Reef (23°S and 14°S) and maintained at one of four temperatures (24, 27, 30, 33 °C). Following >4 weeks acclimation, the spontaneous swimming speeds and activity patterns of individuals were recorded over a period of 12 days. At 24–27 °C, spontaneous swimming speeds of common coral trout were 0.43–0.45 body lengths per second (bls^?1), but dropped sharply to 0.29 bls^?1 at 30 °C and 0.25 bls^?1 at 33 °C. Concurrently, individuals spent 9.3–10.6% of their time resting motionless on the bottom at 24–27 °C, but this behaviour increased to 14.0% at 30 °C and 20.0% of the time at 33 °C (mean ± SE). The impact of temperature was greatest for smaller individuals (<45 cm TL), showing significant changes to swimming speeds across every temperature tested, while medium (45–55 cm TL) and large individuals (>55 cm TL) were first affected by 30 °C and 33 °C, respectively. Importantly, there was some indication that populations can adapt to elevated temperature if presented with adequate time, as the high‐latitude population decreased significantly in swimming speeds at both 30 °C and 33 °C, while the low‐latitude population only showed significant reductions at 33 °C. Given that movement and activity patterns of large mobile species are directly related to prey encounter rates, ability to capture prey and avoid predators, any reductions in activity patterns are likely to reduce overall foraging and energy intake, limit the energy available for growth and reproduction, and affect the fitness and survival of individuals and populations.     

Effects of acute temperature change on the metabolism and swimming ability of juvenile sterlet sturgeon (Acipenser ruthenus,Linnaeus 1758)

The objective of this study was to provide information on changes in the metabolism and swimming ability of juvenile sterlet sturgeon, Acipenser ruthenus, caused by acutely low or high temperatures. Changes in critical swimming speed (U_crit), oxygen consumption rate (MO₂), tail beat frequency (TBF) and tail beat amplitude (TBA) were observed with a Steffensen‐type swimming respirometer, an oxygen electrode and a camera at different swimming speeds at three temperatures: 5°C, 15°C, and 25°C. Fish tested at 5°C and 25°C were maintained at 15°C (near optimal) for one week to simulate conditions below a dam. The U_crit value decreased significantly during acute temperature changes at 5°C and 25°C; U_crit was highest near the optimal temperature. Oxygen consumption rate (MO₂) increased with the swimming speed at 15°C; however, at 25°C and 5°C, the MO₂ decreased with the swimming speed. Both TBA and TBF decreased at 5°C and 25°C compared to values at 15°C. The slopes of the regression lines (TBF/U) at 5°C and 25°C seemed lower compared to 15°C.     

Effects of acute temperature changes on the swimming abilities and oxygen consumption of Ptychobarbus kaznakovi from the Lancang River

Water temperature is known to be a particularly important environmental factor that affects fish swimming performance, but it is unknow how acute temperature changes affect the fish performance of Ptychobarbus kaznakovi. P. kaznakovi in the Lancang River have declined quickly in recent years, and this species was used to examine the effects of acute temperature changes on swimming abilities and oxygen consumption in a Brett‐type swimming tunnel respirometer. The standard metabolic rate (SMR) and routine metabolic rate (RMR) showed 216% and 134% increases, respectively, at 22°C (an acute increase from 17 to 22°C) compared to those at 12°C (an acute decrease from 17 to 12°C). Moreover, the RMR was approximately 1.7, 1.6 and 1.3 times the value of the SMR at 12°C, 17°C and 22°C, respectively. The critical swimming speed (U_crit) of P. kaznakovi at 22°C was 5.45 ± 0.45BL/S, which was 45% higher than that at 12°C (3.77 ± 0.92BL/S). The oxygen consumption rates (MO₂) reached their maximum values at swimming speeds near the U_crit for all the temperature treatments. The maximum metabolic rate (MMR) values at 12°C, 17°C and 22°C were 274.53 ± 142.60 (mgO₂ kg^?1 hr^?1), 412.85 ± 216.34 (mgO₂ kg^?1 hr^?1) and 1,095.73 ± 52.50 (mgO₂ kg^?1 hr^?1), respectively. Moreover, there was a narrow aerobic scope at 12°C compared to that at 17°C and 22°C. The effect of acute temperature changes on the swimming abilities and oxygen consumption of P. kaznakovi indicated that water temperature changes caused by dam construction could directly affect energy consumption during the upstream migration of fish.     

The effect of temperature on energy distribution during the last-larval stadium of the female house cricket, Acheta domesticus

The distribution of energy during the last stadium of the house cricket at two temperatures was the main theme of this study. Food consumption, growth, and oxygen consumption were greater in the first half of the stadium at both 25 and 35°C. An RQ > 1 indicated the conversion of carbohydrates to lipids during the first half of the instar at both temperatures. The duration of the stadium increased from 6 days at 35°C to 14 days at 25°C. The same maximal weight, protein content and lipid content were attained at both 25 and 35°C. A weight loss (mostly in stored lipids) after the midstadium peak weight was greater at the lower temperature. The absorption efficiency and the production of metabolic wastes were not affected by temperature, but the metabolic efficiency was much higher at 35 than at 25°C during the first half as well as the latter half of the stadium. Although during the first half of the stadium more energy was ingested, absorbed, and made available for growth at 25 than at 35°C, only slightly more growth occurred at 25°C. During the last half of the stadium less energy was ingested at 25 than at 35°C, and much more growth occurred at 35°C because of the even greater heat loss at 25 than at 35°C. Therefore at a lower temperature cricket larvae eat slightly more and reach the same maximal weight as at a higher temperature, but they end up smaller because they waste more energy during the extended duration of the stadium at the lower temperature.     

Respiration rates of subitaneous eggs from a marine calanoid copepod: monitored by nanorespirometry

The oxygen consumption rate during embryogenesis of Acartia tonsa subitaneous eggs were measured at different temperatures (10, 15, 17, 21, 24 and 28°C) with nanorespirometry. The oxygen consumption was constant during the embryogenesis but increased rapidly at hatching time. The mean ± SD oxygen consumption rate increased exponentially with temperature and ranged from 0.09 ± 0.04 (10°C) to 0.54 ± 0.09 nmol O₂ egg⁻¹ h⁻¹ (28°C). The mean ± SD Q₁₀-value was 2.51 ± 0.15. Calculations of energy consumption during embryogenesis ranged from 1.86 to 18.28 mJ depending on temperature and development time. We conclude that the effect of temperature on oxygen consumption rate was far less important than the prolonged development time when calculating the energy consumed during embryogenesis.     

Bioenergetic model of planktivorous fish feeding, growth and metabolism: theoretical optimum swimming speed of fish larvae

The feeding activity of an individual fish larva is described by an equation which includes parameters for the area successfully searched, probability of food capture multiplied by the cross-sectional perceptive visual field, larval swimming speed and the time required to consume a unit of food energy. The proportion of ingested food energy used for metabolism increases exponentially with increasing swimming speed. The model predicts that food consumption rate increases asymptotically whereas metabolic rate increases exponentially. This results in a predicted growth rate curve that reaches a maximum at a certain swimming speed and decreases at both higher and lower speeds. The model can be used to predict the influence of type of prey, prey density, water temperature etc. on larval growth. An expression describing how many hours per day fish larvae must forage in order to grow at a certain daily body weight gain allows the limits of environmental conditions for positive, zero and negative growth rate to be set. Results of simulations demonstrated that the optimum swimming speed for maximum growth of coregonid larvae increased with an increase in food density, decrease in water temperature or decrease of prey vulnerability. At optimum ‘theoretical’ swimming speed an increase in water temperature from 5 to 17° C required the food density to be increased from 20 to 80 copepods l^?1 in order to maintain a daily growth increment of 2%. The minimum Artemia density required for maintenance metabolism increased from 10 to 30 items 1¹ over the same temperature increase from 5 to 17° C, and food densities required for 8% growth rates were 26 and 56 Artemia nauplii l^?1 at 5 and 17° C, respectively. Contrary to previous findings, results of the present study suggest that metabolic rates of actively feeding fish larvae may be from 5 to 50 times the standard metabolic rate: earlier studies suggested that a factor of 2–3 may be generally applicable.     

Respirometry and swimming dynamics of the giant australian cuttlefish,sepia apama (mollusca,cephalopoda)

Swimming dynamics of the giant Australian cuttlefish, Sepia apama, were investigated using swimtunnel respirometry. Relationships between jet pressure, fin frequency, swimming speed and oxygen consumption were defined. Laboratory calibration of swimming parameters is necessary to allow estimates of swimming costs in the field.

Jet pressure was the best predictor of oxygen consumption with an averaged equation of MO₂?=?722 (jet pressure)?+?107?r ²?=?0.51. Individually, fin frequency and jet pressure correlated highly to swimming speed, but due to the complicated usage of finning and jetting, the correlation between swimming speed and oxygen consumption was weaker. Cuttlefish were not optimal swimtunnel subjects and could not swim at high speeds for extended periods. At 15°C and a swimming speed of 0.06?m?s^?1, the gross cost of transport was calculated to be 10.1?kg^?1?m?^?1, with a net cost of 4.1?kg^?1?m^?1.     

The Effect of Storage Temperature on Shoot Growth, Flowering, and Carbohydrate Metabolism in Tulip Bulbs

Dry bulbs of the cvs. ‘Apeldoorn’ and ‘Paul Richter’ at stage G of flower development were stored at 5° or 21°C for 2, 4, 6, 8, 10, 12, and 14 weeks, respectively before being planted and forced at 18°C. Samples from each treatment were taken for carbohydrate analysis. The low temperature treatment (5°C) was necessary to obtain satisfactory shoot growth and flowering after planting. The rate of shoot growth and the percentage of flowering bulbs increased with increasing duration of the 5°C treatment. Time of flowering was also precipitated. 12–14 weeks of low temperature treatment seemed optimal. High temperature (21°C), or a short period at 5°C (2–6 weeks), resulted in many non-flowering bulbs, and a very slow shoot elongation when flowering occurred. In the latter case the tips or large areas of the perianths became white, the red pigmentation being prevented. Paper chromatographic analysis of oligosaccharides revealed a substantially increased content of sucrose and fructosyl sucrose (DP ≤ 5) during the first 2–4 weeks of cooling. At the end of 12 weeks at 5°C, the content of oligosaccharides decreased. The increase in the oligosaccharide content was accompanied by a corresponding starch decrease. High temperature storage (21°) led to comparatively slight changes in the sucrose and fructosyl sucrose content of the bulbs. The significance of carbohydrate metabolism in relation to shoot elongation and flowering is discussed.     

The combined effects of temperature,salinity, and declining oxygen tension on oxygen consumption in the marine pulmonate Amphibola crenata (Gmelin, 1791)

Oxygen consumption of Amphibola crenata (Gmelin) was measured in various salinity-temperature combinations (< 0.1‰ to 41‰ salinity and 5 to 30°C) in air, and following exposure to declining oxygen tensions. In all experimental conditions, respiration varied with the 0.44 power of the body weight (sd = 0.14). The aquatic rate was consistently higher than the aerial rate of oxygen consumption, although at 30 °C the two rates were similar. Oxygen consumption increased with temperature up to 25 °C in all salinities; the lowest values were recorded at temperatures below 10 °C and at 30 °C in the most dilute medium. At all exposure temperatures, the oxygen consumption of Amphibola decreased regularly with salinity down to 0.1 ‰, and following exposure to concentrated sea water (41‰). Salinity had the least effect at 15 °C which was the acclimation temperature. In general, all of the temperature coefficients (Q₁₀ values) were low, < 1.65. However, Q₁₀ values above 2.8 were recorded at a salinity of 17.8‰ between 10 and 15 °C. Oxygen consumption of all size classes of Amphibola was more temperature dependent in air than in water and small individuals show a greater difference between their aerial and aquatic rates than larger snails. The rates of oxygen consumption in declining oxygen tensions were expressed as fractions of the rates in air saturated sea water at each experimental salinity-temperature combination. The quadratic coefficient B₂ becomes increasingly more negative with both decreasing salinity and temperatures up to 20 °C. At higher temperatures (25 and 30 °C) the response is reversed such that O₂ uptake in snails becomes increasingly independent of declining oxygen tensions at higher salinities. On exposure to a salinity of 4‰, Amphibola showed no systematic response to declining oxygen tension with respect to temperature. The ability of Amphibola to maintain its rate of oxygen consumption in a wide range of environmental conditions is discussed in relation to its potential for invading terrestrial habitats and its widespread distribution on New Zealand's intertidal mudflats.     

Nahrungsaufnahme,Stoffumsatz und Energiehaushalt des marinen HydroidpolypenClava multicornis

Clava multicornis Forskål (Cnidaria, Hydrozoa) from the North Sea was cultured under a variety of environmental conditions, and quantitative aspects of the following processes examined: food intake, growth, oxygen consumption, losses of material, and food conversion. The experiments were conducted in sea water (salinity 32 ‰) at different constant temperature levels (6°, 11° and 16° C) and different daily food rations. The polyps were fed living larvae of the brine shrimpArtemia salina. Daily rations ranged from 2.3 % (6° C) to 19.0 % (16° C) of the dry weight of the polyp colonies. The food ration essential for minimum growth increased with the test temperature. The calorific value of theArtemia larvae was 5854 cal per g organic dry substance. The calorific values of the colonies ofClava multicornis increased at all 3 test temperatures with ascending daily food rations; they ranged from 5367 to 6003 cal per g organic dry substance. Colony growth was determined in 3 different ways: by measuring the increase in polyp number, the length increase of all polyps of a given colony, and the increase of the dry weight of the organic substance of a given colony. Growth was exponential in all 3 cases. The lowest test temperature, or small daily rations, caused slow growth; the highest temperature, or large daily rations, resulted in rapid growth. Oxygen consumption of individual colonies was measured at 16° C and 3 different daily rations; the colonies showed the same intensity of respiration at all 3 daily rations. A colony of 1.5 mg organic dry substance respired 0.107 ml oxygen per 24 hours, a colony of 5.0 mg, 0.269 ml oxygen. At 11° and 16° C gonophores developed well and were counted; at 6° C no gonophores were observed. The amount of the excrement discharged byC. multicornis at 16° C increased from 26.0 % of the food eaten (minimum daily ration) to 39.3% (maximum daily ration). Gross efficiency increased with falling temperature and rising daily ration. At 16° C, net efficiency increased with rising daily ration. On the basis of the data obtained for gross efficiency, oxygen consumption and excrementation, an energy budget was made up.     

Critical swimming speed of sterlet (Acipenser ruthenus): Does intraspecific hybridization affect swimming performance?

We studied the effect of intraspecific hybridization on swimming performance in sterlet, hypothesizing that such hybridization increases the performance by inducing the hybrid vigor. A total of 12 purebred and hybrid crosses were reproduced from Danube (D) and Volga (V) populations of Acipenser ruthenus. Within each cross, one group of fish was exposed to temperature challenges mimicking the temperature variation in the natural environment during summer. Temperature challenges comprised a constant increase from 19°C to 24°C and then return to 19°C within 12 hr (dT<1°C/hr), and were carried out every third day over the experimental period of 20 days. As a control, fish from each cross were kept at a constant temperature of 19°C. Critical swimming speed (U_crit) was assessed on day 0 (29 days post hatch, dph), 10 (39 dph) and 20 (49 dph). The critical swimming speeds ranged from 5.12 cm/s (1.63 TL/s) to 16.44 cm/s (2.4 TL/s) during the experimental period (29–49 dph). There were no significant differences observed in U_crit between repeatedly temperature challenged and control groups, indicating that the temperature challenge did not alter the swimming performance. The critical swimming speed showed positive relationship with total body length. Comparing intraspecific hybrid crosses with purebred crosses, no significant difference in swimming performance was observed. It is thus concluded that swimming performance is a family specific trait. There is no indication that intraspecific hybridization affects swimming performance nor that close‐to‐natural temperature regimes increase swimming performance.     

Thermal influence on metabolic rates and a bioenergetic budget for Notophthalmus viridescens from southwestern Massachusetts

Notophthalmus viridescens has been reported to overwinter on land in southwestern Massachusetts, whereas these newts hibernate in water in southwestern Ohio. Aquatic and terrestrial metabolic rates of newts from Massachusetts were measured at different exercise speeds and acclimation temperatures in order to better understand their seasonal energetic budgets. Oxygen uptake at 25°C increased with increased swimming and walking speeds and reached a plateau at speeds of 60 and 90 cm/min, whereas at 5°C, oxygen consumption linearly increased with swimming speeds. Aerobic transport costs of the newts thus decreased with increased locomotor speeds at 25°C but remained unchanged when the newts were exercised in water at 5°C. Anaerobic metabolic rates of the newts on land were little affected by acclimation temperature but also increased linearly with walking speeds at both 5°C and 25°C. Anaerobiosis contributed most of the energy for the locomotion of the newts. These newts stored an average of 12 mg lipd/g body mass, which could apparently support their survival at 5°C for 46 days without food on land but only for 18 days in water. These calculations, based on measured metabolic rates and energy reserves, support field observations of red-spotted newts hibernating on land in Massachusetts.     

Thermoregulation on the air–water interface—II: Foot conductance,activity metabolism and a two-dimensional heat transfer model

We used a quasi-adiabatic calorimeter and respirometry apparatus to measure heat loss from the feet of 3- to 4-d-old mallard ducklings (Anas platyrhynchos). We found that, at cool (<20 °C) operative temperatures, foot conductance increased in proportion to operative temperature, T_e, rather than water temperature. We combined these results with those of an earlier study to develop a heat transfer model for swimming ducklings. This model includes separate thermal conductances to air (0.027 W/°C-animal), to water through the down (0.035[1+2.05×10⁻⁷T_e⁴]) W/°C-animal, and to water through the feet (2.01×10⁻⁸T_e⁴ W/°C-animal). The overall conductance by all three routes is only 21% greater when swimming compared to standing in air at the same operative temperature. Interestingly, ducklings can maintain body temperature >39 °C while swimming in 5 °C water, but not when restrained in a calorimeter with 5 °C water. Peak oxygen consumption is greater when swimming, and apparently exercise metabolism substitutes almost completely for thermoregulatory heat production.     

Adaptive variation in energy acquisition and allocation among latitudinal populations of the Atlantic silverside

Understanding the evolution of growth rate requires knowledge of the physiology of growth. This study explored the physiological basis of countergradient variation (CnGV) in somatic growth across latitudinal populations of the Atlantic silverside, Menidia menidia. Energetics of northern (Nova Scotia, Canada) and southern (South Carolina, USA) genotypes were compared across resource levels, temperatures, and fish sizes to identify trade-offs to rapid growth. Offered unlimited resources, genotypes differed in both energy acquisition and allocation. Food consumption, growth, and efficiency of northern genotypes were consistently higher than in southern genotypes, across temperatures and body sizes. Feeding metabolism (specific dynamic action; SDA) was proportional to meal size, differing between genotypes to the extent that food consumption differed. Given limited resources, northern and southern genotypes displayed similar growth, efficiency, routine activity, and SDA across temperatures and fish sizes. Routine metabolism was equal at 17°C and 22°C, yet was significantly higher in northern fish at 28°C. Growth rates in M. menidia do not appear to trade off across environments or body sizes, i.e., at no temperature, ration, or size do southern fish outgrow northern conspecifics. Nor does submaximal growth result from increased costs of maintenance, tissue synthesis, or routine activity. Based on our findings, we propose that CnGV consumption and growth in M. menidia likely result from trade-offs with other energetic components, namely sustained and burst swimming. Received: 26 January 1999 / Accepted: 14 September 1999     

Growth and reproduction of the mosquitofish,Gambusia affinis,in relation to temperature and ration level: consequences for life history

The allocation of energy to growth and reproduction, in relation to temperature and food availability, was investigated in laboratory experiments with the mosquitofish,Gambusia affinis. At constant temperature of 20, 25 and 30°C and ad libitum feeding, specific growth rates increased with increasing temperature at 1.7, 3.1 and 3.4% dry mass day⁻¹, respectively. Growth rates in a cycling temperature regime (20–30°C, ) were faster than in a 25°C constant temperature. As temperature increased from 20 to 30°C, mean age at first reproduction decreased from 191 to 56 days and brood size and mass of offspring increased significantly. Interbrood interval was also temperature dependent; estimates at 25 and 30°C for females >1000 mg were 22.6 and 18.6 days, respectively. Interbrood interval could not be calculated at 20°C. Although fitness was highest at 30°C, females at 25°C invested a greater proportion of surplus energy (growth and reproduction) to reproduction (38%) than at 20 (17%) or 30°C (36%) during the 32-week study. Fish at cooler temperatures began reproduction at a smaller size. Where rations were controlled at low, medium, and ad libitum levels, somatic and gonadal growth increased with increasing temperatures and food availability. The proportion of energy invested in reproduction was highest at 25°C for each comparable ration level. Calculated energy budgets indicated that over the 10-week study, 17–22% of the food energy was invested in growth, 0–7% in reproduction, and 75–83% in respiration and excretory losses, depending on feeding and temperature conditions.     

Functional models for growth and food consumption of Atlantic salmon parr, Salmo salar, from a Norwegian river

1. The chief objectives were to analyse and model experimental data for maximum growth and food consumption of Atlantic salmon parr (Salmo salar) collected from a cold glacier fed river in western Norway. The growth and feeding models were also applied to groups of Atlantic salmon growing and feeding at rates below the maximum. The growth models were validated by comparing their predictions with observed growth in the river supplying the experimental fish.
2. Two different models were fitted, one originally developed for British salmon and the other based on a model for bacterial growth. Both gave estimates for optimum temperature for growth at 18–19 °C, somewhat higher than for Atlantic salmon from Britain. Higher optimal temperature for growth in salmon from a cold Norwegian river than from British rivers does not concur with predictions from the thermal adaptation hypothesis.
3. Model parameter estimates differed among growth groups in that the lower critical temperature for growth increased from fast to slow growing individuals. In contrast to findings for brown trout (Salmo trutta), the optimum temperature for growth did not decrease with decreasing levels of food consumption.
4. A new and simple model showed that food consumption (expressed in energy terms) peaked at 19.5–19.8 °C, which is similar to the optimal temperature for growth. Feeding began at a temperature 1.5 °C below the lower temperature for growth and ended about 1 °C above the maximum temperature for growth. Model parameter estimates for consumption differed among growth groups in a manner similar to the growth models. Maximum consumption was lower for Atlantic salmon than for brown trout, except at temperatures above 18 °C.
5. By combining the growth and food consumption models, growth efficiency was estimated and reached a maximum at about 14 °C for fast growing individuals, increasing to nearly 17 °C for slow growing ones, although it was lower overall for the latter group. Efficiency also declined with increasing fish size. Growth efficiency was generally higher for Atlantic salmon than for brown trout, particularly at high temperature.     

Physiological flexibility: the key to success and survival for Antarctic fairy shrimps in highly fluctuating extreme environments

1. The anostracan fairy shrimp Branchinecta gaini inhabits one of the most hostile environments on earth, living in pools and lakes in Antarctica. Between January 2002 and January 2003 temperatures in two pools where B. gaini are extremely abundant on Adelaide Island ranged from ?18.6 to ?15.7 °C in winter, to 19.4 to 17.1 °C in summer, whilst air temperatures ranged from ?34 to 6.3 °C. 2. Branchinecta gaini survives winter as cysts, but endures large summer temperature fluctuations as adults. Cysts froze between ?24.4 and ?25.7 °C. In experiments adults survived 0–10 °C with no mortality for 1 week, 25 °C for nearly 48 h with 50% mortality, and at 32 °C complete mortality occurred in <1 h. 3. Oxygen consumption (M?O₂) in B. gaini approximately doubled for every 10 °C temperature rise (Q₁₀ = 2.04) up to 20 °C where it reached a peak. Females had, on average 19% higher M?O₂ than males. Females also had greater metabolic scopes, (maximum–minimum M?O₂ across temperatures was ×3.6 for females, ×3.1 for males). 4. Ventilation frequency increased linearly with temperature, and did not decline at 25 °C, indicating animals were ‘trying’ progressively harder to supply oxygen to tissues, and oxygen deficiency was the probable cause of death. Females had a higher ventilation frequency than males (8.6–17.1% higher) and they also exhibited greater scope to raise ventilation frequency (×2.4 for females versus ×1.5 for males). 5. Great metabolic flexibility allows B. gaini to exploit extreme, highly fluctuating environments, and larger ventilatory and respiratory scopes allow females to survive higher temperatures than males. Because of this flexibility their prospects for coping with physical environmental change are high.     

Influence of rearing temperature on triacylglycerol storage in the pea aphid,Acyrthosiphon pisum

Total fatty acids in the pea aphid reared at low temperatures increased significantly compared to that at high rearing temperatures. This change is reflected in a large increase of myristic acid, which occurs exclusively in triacylglycerols. When aphids were moved from 25°C to a lower rearing temperature at 10°C, saturated fatty acids accumulated over time, reaching a maximum at 16th day. When aphids were moved to 4°C, a temperature below the developmental threshold, those aphids did not accumulate saturated fatty acids. Similar results were observed when aphids were exposed to sequential decrease in rearing temperature. However, both total fatty acids and myristic acid in the aphids from the treatments of sequential decreasing rearing temperature were significantly higher compared to those in the aphids from the treatments of sudden decreasing rearing temperature. This result, therefore, supports the hypothesis that cold‐adapted aphids can survive under threshold temperature for a longer period of time than noncold‐adapted aphids. Acetyl‐CoA carboxylase activity in the aphids at 25°C was twofold higher than that in the aphids at 10°C, whereas fatty acid synthase activities in the aphids reared at 25 and 10°C are similar. Aphids reared at 10°C showed a threefold reduction in reproduction rates. This reduced production of new nymphs reduces energy demand and would allow for accumulation of energy in the form of triacylglycerols. Therefore, the increased level of saturated fatty acids in aphids reared at low temperature is probably related to lower utilization of fatty acids rather than increased rates of biosynthesis.     

Interaction of Growth Retardants and Temperature in Growth, Flowering, Regeneration, and Auxin Activity of Begonia × cheimantha Everett

Soil application of CCC reduced stem and leaf growth in Begonia plants. This effect was evident with all concentrations tested at 18°C, whereas at 21 and 24°C no growth–retarding effect was observed with 2 × 10^?2 M CCC, and with 5 × 10^?3 M growth was even stimulated. Flowering was promoted by CCC in long day and neur–critical temperature, particularly under low light intensity in the winter. The formation of adventitious buds in leaves of plants grown at 21 and 24°C was stimulated when the plants received 5 × 10^?2 and 2 × 10^?2 M CCC, while 8 7times; 10^?2 M was inhibitory. In plants grown at 18°C bud formation was inhibited by all CCC concentrations. Root formation in the the leaves was usually stimulated by high CCC concentrations, while root elongation was reduced. The level of ether–extractable. acidic auxin (presumably IAA) in the leaves was lowered by CCC treatment of the plants, hut this required higher CCC concentrations at higt than at low temperature. When applied to detached leaves CCC stimulated bud formation at concentrations ranging from 10^?4 to 10^?2 M in leaves planted at 18 and 21°C. At 24°C budding was inhibited by 10^?2 M CCC, the lower concentrations being stimulatory also at this temperature. Root formation and growth were not much affected by CCC treatment of the leaves, but increased with the temperature. Soil application of Phosfon (4 × 10^?4 M) had no effect on growth and flowering, nov did it affect the subsequent regeneration of buds and roots in the leaves. In detached leaves Phosfon stimulated bud formation with au optimum at 10^?6 M. Root formation was stimulated by Phosfon at all temperatures, the optimal concentration being 10^?5 M, whereas root length was conversely affected. Foliar application of B-995 to intact plants and treatment of detached leaves greatly inhibited the formation of buds and had little effect on root formation. B-99D reduced the growth and delayed flowering in the plants.