Effect of temperature, salinity, and dissolved oxygen concentration upon respiratory activity of the larva of Philanisus plebeius (Trichoptera)

Records of oxygen uptake of marine larvae of Philanisus in different salinities and at different temperatures show that a maximum is reached in normal sea water at 25°C. A close relation exists between oxygen uptake and the rhythm of ventilatory movements, leading to the conclusion that changes in oxygen uptake are affected by alteration in the frequency rather than the amplitude of the ventilatory movements. Ventilation of the case is stimulated by a fall in oxygen tension but inhibited at low oxygen levels. The ventilatory efficiency of Philanisus in saturated sea water at 25°C is about 26 per cent.     

Effects of development, temperature and salinity on metabolism in eggs and yolk-sac larvae of milkfish, Chanos chanos (Forsskål)

Oxygen uptake rates and yolk-inclusive dry weiGhts were measured during the egg and yolk-sac larval stages of milkfish, Chanos chanos (Forsskal). Oxygen uptake by eggs and yolk-sac larvae was measured to assess the effects of four salinities (20,25,30,35 ppt) at 28°C. The effects of three temperatures (23,28,33°C) on oxygen uptake by yolk-sac larvae were determined at a salinity of 35 ppt. Dry weights were measured throughout embryonic development at 28°C and the yolk-sac stage at 23.28 and 33°C.
Oxygen uptake rates of eggs increased more than fivefold during embryogenesis (0.07±0.03 to 0.40 ± 03 μl O₂ egg ⁻¹ h ⁻¹;blastula to prehatch stage). Larval oxygen uptake did not change with age but was affected by rearing temperature (0.33 ± 0.08, 0.44 ± 0.07 and 0.63 ± 0.13 μl O₂ larva ⁻¹ h⁻¹ at 23, 28 and 33°C, respectively; Q₁₀= 1.93). Acute temperature changes from 28 to 33°C caused significant increases in oxygen uptake by embryos (Q ₁₀= 1.69–3.58) and yolk-sac larvae (Q ₁₀=2.55). Salinity did not affect metabolic rates.
Dry weight of eggs incubated at 28°C decreased 13% from fertilization to hatching. Incubation temperatures from 23–33°C did not affect dry weights at hatching. Rearing temperatures significantly affected the rate of larval yolk absorption (Q ₁₀= 2.25).     

Temperature-related fluctuations in the timing of emergence and pupation of Windermere alder-flies over 30 years

1. From 1966 to 1995, dates were recorded when adult alder-flies, Sialis lutaria L., were first seen (30-year range: 23 April – 25 May), 50% of the maximum density occurred (4 May – 4 June), and maximum density occurred (11 May – 17 June) along 200 m of Windermere shore. These emergence dates occurred at similar temperatures, estimated by mean values for both the emergence date and the week prior to emergence. The latter was the least variable at 10.1 °C (95% CL ± 0.37) for start of emergence, 11.2 °C (± 0.49) for 50% maximum density, 14.2 °C (± 0.51) for maximum density.
2. Final-instar larvae pupated in damp soil just above the water line. As laboratory temperatures were increased slowly from an initial 5 °C, the cumulative number of larvae leaving the water to pupate increased. A quadratic equation described this relationship from a threshold temperature of 7.2 °C to completion at 14.0 °C (50% point, 9.3 °C). The relationship between successful pupations and constant temperatures in the laboratory was well described by a quadratic equation with an optimum 14.9 °C (over 90% success) and no success outside the range 7–23 °C. A negative power-function described the relationship between days required for pupation and temperature, ranging from c . 28 days at 8.2 °C to c . 4 days at 22.1 °C.
3. Dates for larvae leaving the lake to pupate were back-calculated from dates for adult emergence, using the power-function for pupation time. Mean temperatures for estimated dates on which larvae left the lake to pupate were less variable than those for adult emergence, being 7.5 °C (± 0.20) for the start of pupation, 9.4 °C (± 0.16) for 50% maximum density, 13.7 °C (± 0.16) for maximum density. These values are similar to those obtained in the laboratory and can be used to predict pupation and adult emergence for different temperature regimes.     

The relative importance of temperature and diet to larval development and adult size of the winter stonefly, Soyedina carolinensis (Piecoptera: Nemouridae)

SUMMARY. 1. Soyedina carolinensis Claassen, a leaf shredding stonefly, was reared in a series of three laboratory experiments from early instar to adult on different species of deciduous leaves and at various constant and fluctuating temperature regimes.
2. Experiment 1, which involved rearing larvae on fourteen different leaf diets at ambient stream temperatures, showed that diet significantly affected larval growth and adult size but did not affect overall developmental time.
3. Experiment 2, which involved rearing larvae on five different leaf diets at each of three fluctuating temperature regimes (viz ambient White Clay Creek (WCC), ambient WCC+3°C, and ambient WCC+6°C), showed that: (i) adding 6°C to the normal temperature regime of WCC was lethal to 99% of the larvae regardless of diet; and (ii) warming WCC by 3°C did not affect developmental time but did significantly reduce adult size relative to adults reared at WCC temperatures on certain diets.
4. Experiment 3, which involved rearing larvae on five different leaf diets at each of five constant temperatures (viz 5, 10, 15, 20, 25°C), showed that: (i) temperature significantly affected the mortality, growth, and development time of larvae whereas diet only affected larval growth and mortality; (ii) temperatures at or near 10°C yielded maximum larval growth and survival for most diets; (iii) at 5°C, larval mortality was high and growth was low resulting in a few small adults for most diets; (iv) larval mortality was at or near 100% at 15°C regardless of diet; and (v) no larvae survived at 20 and 25°C.     

Natural thermal stress and heat-shock protein expression in Drosophila larvae and pupae

1. Whether Drosophila larvae and pupae naturally experience temperatures that can cause heat damage or death is poorly understood, but bears directly on numerous investigations of the thermal biology and heat-shock response in Drosophila . Accordingly, the temperatures of necrotic fruit, which Drosophila larvae and pupae inhabit, the temperatures of larvae and pupae outside the laboratory, and the levels of the heat-shock protein hsp 70 expressed by larvae in nature were examined.
2. When necrotic fruit was sunlit, internal temperatures rose to levels that can harm indwelling insects. Fruit size and evaporative water loss affected these temperatures. Temperatures of larvae and pupae in the field commonly exceeded 35 °C, with living larvae recorded at >44°C and pupae at >41°C. Natural mortality was evident, presumably because of heat.
3. In the laboratory, these temperatures kill larvae rapidly, with LT₅₀s (time taken for half the sample to be killed) of 30 min at 39 °C, 15 min at 40 °C and 8·5 min at 41 °C. Gradual transfer from 25°C to these temperatures resulted in no lesser mortality than did direct transfer.
4. Hsp 70 levels in lysates of whole larvae were measured by ELISA (enzyme-link immunosorbent assay) with an hsp 70-specific antibody. For larvae within necrotic apples experimentally transferred from shade to sun and within necrotic fruit in situ , hsp 70 levels equalled or exceeded levels detected in parallel laboratory studies of whole larvae or cells in culture.
5. These data provide an ecological context for studies of thermal stress and the heat-shock response in Drosophila that has heretofore been lacking.     

Consumption and gut evacuation rate of laboratory‐reared spotted seatrout (Sciaenidae) larvae and juveniles

The temperature and mass dependence of maximum consumption rate was measured for larval and early juvenile spotted seatrout Cynoscion nebulosus . Maximum consumption ( C _MAX) estimates were obtained from feeding and gut evacuation experiments on larvae (3·8–19 mm standard length, L _S) at three temperatures (24, 28 and 32° C), and maximum consumption experiments on juveniles at three temperatures (20, 26 and 32° C). Feeding levels were determined for larvae fed live prey ( Brachionus plicatilis and Artemia salina ) ad libitum . The midgut and total evacuation times were estimated for fish feeding continuously and discontinuously using alternate meals of tagged and untagged live prey. Temperature and fish size had significant effects on gut evacuation and consumption. The gut evacuation time increased with increasing fish size, and decreased with increasing temperatures. Mass‐specific midgut contents increased for small larvae <0·156 mg dry mass ( M _D)( c . 4 mm L _S), and decreased for larger larvae and juveniles. Maximum consumption was modelled by fitting a polynomial function to a reduced dataset of individuals feeding at high levels. The C _MAX model predicted an initial increase in specific feeding rate from 70 to 155% M _D day⁻¹ for small larvae, before declining for larger larvae and juveniles.     

Oxygen uptake and local Po2 profiles in submerged larvae of phaeoxantha klugii (Coleoptera: Cicindelidae), as well as their metabolic rate in air

We studied whether oxygen uptake from the surrounding water might enhance survival in submerged third instar larvae of Phaeoxantha klugii, a tiger beetle from the central Amazonian floodplains. Local oxygen partial pressures (Po(2)) were measured with microcoaxial needle electrodes close to larvae submerged in initially air-saturated still water. The Po(2) profiles showed that the larvae exploit oxygen from the aquatic medium. Metabolism in the air of more or less resting larvae was determined by measuring the rate of CO(2) production (sV dot co2) with an infrared gas analyzer at 29 degrees C. The sV dot co2 was around 1.8 mu L g(-1) min(-1), equivalent to an oxygen consumption rate (sV dot o2) of 1.8-2.6 mu L g(-1) min(-1). Oxygen consumption (V dot o2) of individually submerged larvae measured in closed respiration chambers at 19-10.3 kPa Po(2) (initially air saturated, 29 degrees C) ranged between 0.05 and 0.2 mu L min(-1) and was not correlated with body mass. The sV dot o2 ranged between 0.1 and 0.4 mu L min(-1), that is, 4%-22% of the metabolic rate measured in air. Mean V dot o2 decreased with declining Po(2); however, some individuals showed contrary patterns. V dot o2 was additionally measured in dormant larvae, in larvae submerged for 1-2 d in open water or for 30-49 d within sediment, as well as in larvae exposed to anoxia before the measurements. The range of V dot o2 was similar in all groups, indicating that the larvae exploit oxygen from the water whenever available. Similar V dot o2 across the whole range of body mass investigated (0.31-0.76 g) suggests that oxygen uptake occurs by spiracular uptake. Assuming that larvae survive for some time at rates comparable to depressed metabolic rates reported for other insect species, it can be concluded that oxygen uptake from water can sustain aerobic metabolism even under quite severe hypoxia. It might therefore play an important role for survival during inundation periods.     

Cold shock and cold tolerance in larvae and pupae of the blow fly, Lucilia sericata

Abstract.  Understanding the effects of low winter temperatures on mortality is essential in the development of a full understanding of the long-term population dynamics of any insect. The present study aims to examine the survival of pupae and larvae of the blow fly, Lucilia sericata , at overwintering temperatures. Groups of pupae and diapausing and nondiapausing third-stage larvae of L. sericata are maintained in cooled incubators at either 3 °C and 6 °C. Groups are removed from the incubators at 3–4-day intervals and transferred either to−8 °C or to 25 °C. After 1 h in the freezer, the larvae and pupae exposed to this cold-shock are also transferred to 25 °C. Larvae and pupae are then allowed to continue development and the number of adults emerging from each group is counted. The results demonstrate that survival decreases linearly with the period of exposure at both 3 °C and 6 °C. Mortality is higher at 3 °C than at 6 °C and, in groups that receive the cold shock, cold-shock reduces emergence by over 50%. However, there is no consistent tendency for diapausing larvae to survive prolonged cold or cold shock better than other life-cycle stages. The results suggest that the facultative development of an overwintering diapause stage in L. sericata does not appear to be an adaptation to enhance cold tolerance or resistance to cold shock. It is concluded that the survival of overwintering L. sericata is likely to be relatively less affected by low temperatures than it is by, for example, biotic factors, particularly given the buffered soil environment and short time-scales over which periods of cold act.     

The metabolic and biochemical responses of tropical whitespotted bamboo shark Chiloscyllium plagiosum to alterations in environmental temperature

The capacity of tropical whitespotted bamboo sharks Chiloscyllium plagiosum to metabolically compensate, at both the whole‐animal and biochemical levels, to prolonged exposure to temperatures higher (30° C) and lower (20 and 15° C) than their native temperature (24·5° C) was examined. As expected, whitespotted bamboo shark oxygen consumption increased upon exposure to 30° C and decreased at 20 and 15° C. Initial changes in oxygen consumption were maintained even after months at the experimental temperature, indicating that whitespotted bamboo sharks did not compensate metabolically to the experimental temperatures. Maximal activities and thermal sensitivity of citrate synthase and lactate dehydrogenase from whitespotted bamboo shark white locomotor muscle were similar between control animals maintained at 24·5° C and those maintained at 15° C, indicating that cold‐exposed animals did not compensate at the biochemical level. Similarly, lactate dehydrogenase activity did not change following prolonged exposure to 30° C. White muscle from whitespotted bamboo sharks maintained at 30° C had significantly lower citrate synthase activity than did control animals. This result was surprising given the lack of metabolic compensation at the whole‐animal level. Overall, whole‐animal oxygen consumption measurements supported the hypothesis that animals from thermally stable environments lacked the capacity to metabolically compensate to altered temperatures. Enzymatic results, however, suggested that the metabolic potential of muscle could change following temperature acclimation even in the absence of metabolic compensation at the whole‐animal level.     

Elevated temperature reduces the respiratory scope of coral reef fishes

The capacity for marine fishes to perform aerobically (aerobic scope) is predicted to control their thermal tolerance and, thus, the impact that rapid climate change will have on their populations. We tested the effect of increased water temperatures on the resting and maximum rates of oxygen consumption in five common coral reef fishes at Lizard Island on the northern Great Barrier Reef, Australia. All species exhibited a decline in aerobic capacity at elevated water temperatures (31, 32 or 33 °C) compared with controls (29 °C); however, the response was much stronger in two cardinalfishes, Ostorhinchus cyanosoma and O. doederleini , compared with three damselfishes, Dascyllus anuarus, Chromis atripectoralis and Acanthochromis polyacanthus . Aerobic scope of the two cardinalfishes was reduced by nearly half at 31 °C compared with 29 °C, and virtually all capacity for additional oxygen uptake was exhausted by 33 °C. In contrast, the three damselfishes retained over half their aerobic scope at 33 °C. Such differences in thermal tolerance between species, and possibly families, suggest that the community structure of reef fish assemblages might change significantly as ocean temperatures increase. Populations of thermally tolerant species are likely to persist at higher temperatures, but populations of thermally sensitive species could decline on low-latitude reefs if individual performance falls below levels needed to sustain viable populations.     

Thermal acclimation of swimming performance in newt larvae: the influence of diel temperature fluctuations during embryogenesis

1.  Thermal acclimation is one of the basic strategies by which organisms cope with thermal heterogeneity of the environment. Under predictable variation in environmental temperatures, theory predicts that selection favours acclimation of thermal performance curves over fixed phenotypes.
2.  We examined the influence of diel fluctuations in developmental temperatures on the thermal sensitivity of the maximal swimming capacity in larvae of the alpine newt, Triturus alpestris .
3.  We incubated newt eggs under three thermal regimes with varying daily amplitudes (1, 5 and 9 °C) and similar means (17·6–17·9 °C), and accordingly we measured the swimming speed of hatched larvae at three experimental temperatures (12, 17 and 22 °C), which they would normally experience in their natural habitat.
4.  Embryonic development under low and middle temperature fluctuations produced larvae with similar swimming speeds across experimental temperatures. In contrast, the most fluctuating regime induced development of phenotypes, which at 12 °C swam faster than larvae developed under moderate diel fluctuations.
5.  Our results provide evidence that diel temperature fluctuations induce acclimation of thermal dependence of locomotor performance. In ectotherms experiencing diel cycles in environmental temperatures, this plastic response may act as an important pacemaker in the evolution of thermal sensitivity.     

Survival of the first stage larva of the metastrongyloid nematode Elaphostrongylus rangiferi under various conditions of temperature and humidity

First-stage larvae of E. rangiferi kept in water at 50°C died within 80 minutes, while at 6° the last larvae died between day 180 and 210. The time it took to reach 1_x= 0.5 (half of the larvae dead) at various temperatures between 6° and 50° was well described by the exponential function y = 614.6e^−0.15x, giving a value of 615 days to reach 1_x= 0.5 at 0°C. There was no clear decrease in the survival of larvae frozen at −20° in faeces and in water, and at −80° in faeces after 360 days. When subjected to repealed freezing and thawing, all larvae died within 77 days. When kept in air at RH = 20% and 22°C, all larvae died within 11 days, while when frozen (−20°C) in air at RH approx. 0%, 1_x stayed at approx. 0.5 from day 5 to day 16.     

The effects of temperature and season on the O2 consumption of third-instar larvae of the goldenrod gall fly (Eurosta solidaginis)

Abstract. Third-instar larvae of the goldenrod gall fly ( Eurosta solidaginis Fitch) live inside ball galls on goldenrod plants from summer to the following spring.Because galls are highly exposed to the weather, larvae experience substantial variations in body temperature.This study documents the oxygen consumption of gall fly larvae with regard to the effects of ambient temperature, seasonal conditioning, and prior exposure to subzero temperature.The body mass of larvae doubles between the late summer and the autumn; it subsequently undergoes a modest decline by early winter.The O₂, consumption of field-acclimatized larvae increases with ambient temperature, especially between 0 and 10°C (Q₁₀= 2.6-3.4).The thermal sensitivity of metabolism declines at higher ambient temperatures, most notably during the autumn/early winter.After exposure to 15°C for 1 week, autumn and early winter larvae maintain much lower rates of O₂ consumption than do late summer specimens.Prior exposure to -5°C for 24 h did not influence the O₂ consumption of larvae.Low thermal sensitivity of O₂ consumption, especially at higher ambient temperatures, is an energy-sparing mechanism during seasonal inactivity.Indeed, the persistence of this metabolic pattern in larvae exposed to 15°C suggests that they have entered a state of diapause.     

Oxygen requirements of larvae of the smallmouth bass, Micropterus dolomieui Lacépède

Smallmouth bass larvae became highly sensitive to oxygen deficiency on the second day after hatching and continued so to the 10th day. During this period they could not survive exposure to 1 mg O₂ l^–1 for 3 h at 20° C, and many were killed within 1 h. At 2 mg O₂ l^–1 half the larvae survived 3 h at 20° C; at 2.5 mg l^–1 most survived, and at 3.5 mg l^–1 all survived. Resistance to oxygen deficiency was regained by the 11th day, the majority of the larvae withstanding a 3-h exposure at 1 mg O₂ l^–1. At 25° C the effects of low oxygen concentration were intensified. At 3 and 4 mg O₂ l^–1 and 20° C the normally quiescent larvae became very active, even swimming to the surface 5 or 6 cm above the substrate. Increasing the temperature increased this response. Smallmouth larvae were more sensitive than large-mouth bass larvae to oxygen deficiency.     

The effect of temperature on the ability of Tilapia mossambica Peters to enter deep water

The ability of adult Tilapia mossambica Peters to enter deep water was determined at 15, 22 and 30°C. At 30°C adults compensate to about 20m depth but at 15°C to only 7 m. Compensation is more rapid at high than at low temperatures. T. mossambica haemoglobin has a marked Root effect which is the same at 22 and 30°C. The oxygen affinity of the haemoglobin is higher at 15°C than at 30°C. There was no measurable difference in the rate of passive oxygen diffusion across the swimbladder wall in the temperature range 15–30°C. It is concluded that the ability to enter deeper water at higher temperatures is related to decreased oxygen affinity of the haemoglobin and higher rates of oxygen secretion and blood circulation.     

Temperature effects on bioconcentration of DDE by Daphnia

1. Lake temperatures vary with season, latitude, elevation and as a result of thermal pollution. In addition, lake temperatures may increase with global warming. Radiotracer experiments were conducted to determine the effects of temperature on the bioaccumulation of lipophilic organic contaminants by zooplankton. Daphnia pulex were exposed to ¹⁴C-labelled DDE, a stable metabolite of the organochlorine pesticide DDT, in particle-free water for 24 h. An increase in temperature from 5 to 25 °C resulted in a 314% increase in bioconcentration factor (the ratio of contaminant concentration in the organism to contaminant concentration in the water).
2. To mimic the fluctuating temperatures experienced by zooplankton during diel vertical migration, we conducted experiments in which animals were exposed to 25 °C for 12 h in the light, then 15 °C for 12 h in the dark. Exposure to this fluctuating temperature regime for 48 h resulted in a 27–33% increase in bioconcentration factor relative to a constant 20 °C control.
3. Live animals accumulated more than twice the amount of DDE than freshly killed animals, indicating that the activity of the organism is important in bioconcentration. This finding sheds light on the possible mechanisms for the increase in bioconcentration at higher constant temperatures. Daphnia pump more water through their branchial chambers at higher temperatures. Thus, if the thoracic limbs are an important site of contaminant uptake, then animals are exposed to more contaminant molecules at higher temperatures. Other possible mechanisms include changes in the thickness of the diffusive boundary layer and changes in cell membrane permeability.     

Temperature effects on bioconcentration of DDE by Daphnia

1. Lake temperatures vary with season, latitude, elevation and as a result of thermal pollution. In addition, lake temperatures may increase with global warming. Radiotracer experiments were conducted to determine the effects of temperature on the bioaccumulation of lipophilic organic contaminants by zooplankton. Daphnia pulex were exposed to ¹⁴C-labelled DDE, a stable metabolite of the organochlorine pesticide DDT, in particle-free water for 24 h. An increase in temperature from 5 to 25 °C resulted in a 314% increase in bioconcentration factor (the ratio of contaminant concentration in the organism to contaminant concentration in the water).
2. To mimic the fluctuating temperatures experienced by zooplankton during diel vertical migration, we conducted experiments in which animals were exposed to 25 °C for 12 h in the light, then 15 °C for 12 h in the dark. Exposure to this fluctuating temperature regime for 48 h resulted in a 27–33% increase in bioconcentration factor relative to a constant 20 °C control.
3. Live animals accumulated more than twice the amount of DDE than freshly killed animals, indicating that the activity of the organism is important in bioconcentration. This finding sheds light on the possible mechanisms for the increase in bioconcentration at higher constant temperatures. Daphnia pump more water through their branchial chambers at higher temperatures. Thus, if the thoracic limbs are an important site of contaminant uptake, then animals are exposed to more contaminant molecules at higher temperatures. Other possible mechanisms include changes in the thickness of the diffusive boundary layer and changes in cell membrane permeability.     

Lack of metabolic thermal compensation during the early life stages of ocean pout Zoarces americanus (Bloch & Schneider) : a benthic, cold-water marine species

The present study investigated the metabolic response of young ocean pout Zoarces americanus to temperature acclimation (3 v. 11° C), and to acute changes in water temperature from 3 to 17° C. The Q ₁₀ value for standard metabolic rate between acclimation temperatures was 5·3, warm-acclimated fish displayed higher rates of oxygen uptake at all temperatures during the acute thermal challenge, and changes in whole-body citrate synthase activity were qualitatively similar to those seen for metabolism. These results indicate that, in contrast to temperate species, young ocean pout from Newfoundland do not show thermal compensation in response to long-term temperature changes.     

THE EFFECT OF TEMPERATURE ON EGGS AND IMMATURE STAGES OF CULEX ANNULIROSTRIS SKUSE (DIPTERA: CULICIDAE)

Abstract
No immature stages of Culex annulirostris were found during field sampling in 1979–1980 when the average water temperature was < 17 °C; they reappeared when the average water temperature was 19 °C and reached the peak density (mean 107 immatures/cylinder) at 26.5 °C.
The effect of 6 temperatures (15–40°C) on egg hatching, development and survival of the immature stages of Cx annulirostris in the laboratory showed that at 15 and 40°C, eggs failed to hatch and larvae died in the first instars. The optimum temperatures for egg hatching and the survival of immature stages were 25 and 30°C. At these temperatures, 85 and 82% respectively of egg rafts hatched, the mean number of larvae per raft was 258 ± 9.8 and 260 ± 11.4 with immature survival of 83.5 and 79.0% respectively. Mean time to hatch at 20–35°C ranged from 1.2 d (35°C) to 2.9 d (20 °C). Developmental times from first instar to adult ranged from 7.1 d (35 °C) to 25.2 d (20 °C). The threshold for development of the immatures was 15.6 ± 2.5°C and the thermal constant was 142.9 ± 26.5 day—degrees (incubation temperatures 20–35°C). At less suitable temperatures of 20 and 35 °C, hatching (57.5 and 45%), number larvae per raft (mean 139.8 ± 9.8 and 102.6 ± 14.2) and survival were low.