Effects Of Acute Temperature Change Research Articles

Effects of acute temperature change on California moray prey manipulation and transport behavior

California moray eels, Gymnothorax mordax, are benthic predatory residents of southern California kelp forest ecosystems. California morays around Catalina Island move vertically through the water column to feed, exposing them to a wide range of temperatures. For a predatory fish, morays have a relatively large prey handling repertoire that enable them to manipulate their prey before swallowing. Prey manipulation behaviors include shaking, spinning, knotting, and ramming prey against other objects. Morays also have observable transport mechanics where they protract and retract their pharyngeal jaws to swallow prey. We examined prey manipulation and transport behaviors at four temperature treatments that simulated the range of environmental temperatures morays encounter in the wild. We hypothesized that higher temperatures will increase the prevalence, duration, and rate of whole body prey manipulation behaviors and decrease the duration of prey transport time. Previous temperature studies focused on fishes occupying intermediate trophic levels. Therefore, understanding how acute temperature affects feeding behavior of the California moray eel, an abundant predatory fish, is especially important, as changes in environmental temperature may have disproportionate effects in their marine community. Five morays were acutely exposed to 15, 18, 21, 24 °C temperatures and their subsequent feeding behaviors were filmed and quantified. Individuals were offered the same relative prey mass (15 %) in relation to their body mass throughout the study. We compared the number of times each prey manipulation behavior occurred, the mean time morays employed each behavior, and the rate (number of times per second) each behavior was performed across different temperatures. Our data demonstrates that absolute time spent knotting varies significantly across temperature. Knotting, often used to remove pieces from larger prey, was most frequent at 21 and 24 °C. The average duration of knotting also increased with temperature. The rates of prey manipulation behaviors did not vary significantly with temperature. Finally, transport behavior did not vary across treatments. Our study shows that knotting behavior in the California moray is responsive to environmental temperatures and that morays may be able to manipulate larger prey in warmer waters. These behavioral data may have important implications for predator-prey relationships under dynamic and future ocean conditions.

Effects of Acute Temperature Change Associated with Handling Practices on Metabolic Rate Stabilization in Two Centrarchids

AbstractSportfishing and hatchery practices routinely subject fish to acute temperature changes through placement of fish in live wells and normal handling and transportation procedures. Acute temperature changes alter metabolic rate in ectotherms; however, the rapidity of the response to reach a new homeostatic state is not well known. Therefore, the response duration in metabolic rate after acute temperature change was measured in two centrarchid species, the Largemouth Bass Micropterus salmoides and Redear Sunfish Lepomis microlophus, which are representative of two different body shapes and are both commonly pursued in recreational fishing and reared in hatcheries. Largemouth Bass were acclimated to either 20°C or 30°C, and Redear Sunfish were acclimated to 24°C. Aerobic metabolic rate was measured immediately after acute temperature change (−4, +0, or +4°C) and was measured repeatedly in cycles of 5.5 or 10.0 min, respectively, until the metabolic rate stabilized. In Largemouth Bass, the metabolic rate stabilized similarly or more slowly following a moderate high‐temperature shock (+4°C; 44 min) compared to transfer to conditions with no temperature change (+0°C) or a moderate low‐temperature shock (−4°C; 16–48 min). In contrast, the metabolic rate in Redear Sunfish stabilized faster after transfer to +4°C (15 min) than after transfer to −4°C or +0°C (both 31 min), possibly because the elevated metabolic rate after transfer was sustained. Notably, for both species, metabolic rates stabilized at a generally lower level after transfer to −4°C than after transfer to +0°C or +4°C. Therefore, the duration until stabilization of metabolic rate after acute temperature change may depend upon species and acclimation temperature, although for both species examined, the energy savings in reduced metabolic rates after moderate cold shock may be beneficial for recovery from sportfishing or hatchery practices.

Gene expression profile of the taimen Hucho taimen in response to acute temperature changes

The endangered cold-water fish species taimen (Hucho taimen) suffer acute temperature changes in culture and wild conditions. Understanding the effects of acute temperature changes on physiological processes of this species is essential for aquaculture practices and conservation. Liver transcriptomic profiles of the taimen (n = 24) exposed to acute temperature decrease (from 20 °C to 10 °C) and acute temperature increase (from 10 °C to 20 °C) was evaluated using high-throughput RNA-Sequencing. Samples were collected at day 0, 1, 7 and 35 in both treatments. Compared to day 0, the total numbers of differentially expressed genes (DEGs) in the taimen after acute temperature decrease were 173, 226 and 42 at day 1, 7 and 35, respectively, and the total numbers of DEGs following acute temperature increase were 260, 253 and 282 at day 1, 7 and 35, respectively. Particularly, 14 key regulatory genes were commonly found between both acute temperature treatments. Functional analysis based on the commonly identified DEGs revealed important metabolic pathways related to metabolism and immune function, suggesting a specific response mechanism of taimen against cold and heat shock. The results may assist in developing management strategies for stress mediation caused by acute temperature changes in the taimen and other cold water fish.

Mitochondrial Costs of Being Hot: Effects of Acute Thermal Change on Liver Bioenergetics in Toads (Bufo bufo).

Global climatic warming is predicted to drive extreme thermal events, especially in temperate terrestrial environments. Hence, describing how physiological parameters are affected by acute temperature changes would allow us to understand the energy management of organisms facing such non-predictable and constraining events. As mitochondria play a key role in the conversion of energy from food into ATP but also produce harmful reactive oxygen species, the understanding of its functioning is crucial to determine the proximal causes of potential decline in an animal’s performance. Here we studied the effects of acute temperature changes (between 20 and 30°C) on mitochondrial respiration, ATP synthesis rate, oxidative phosphorylation efficiency (ATP/O), and H2O2 generation in isolated liver mitochondria of a terrestrial ectotherm, the common toad (Bufo bufo). Using succinate as the respiratory substrate, we found that the mitochondrial rates of oxygen consumption, ATP synthesis, and H2O2 generation increased as the temperature increased, being 65, 52, and 66% higher at 30°C than at 20°C, respectively. We also found that the mitochondrial coupling efficiency (ATP/O) decreased, while the oxidative cost of ATP production (H2O2/ATP ratio) increased. The present results further indicate that between 40 and 60% of temperature effects on mitochondrial ATP production and H2O2 generation was at minima driven by an action on the oxidative capacity of the mitochondria. These results suggest that B. bufo may need to allocate extra energy to maintain ATP production and protect cells from oxidative stress, reducing the energy allocable performances.

Metabolic scope and hypoxia tolerance of Atlantic croaker (Micropogonias undulatus Linnaeus, 1766) and spot (Leiostomus xanthurus Lacepède, 1802), with insights into the effects of acute temperature change

Dynamic conditions in estuaries result in fish experiencing acute changes in temperature and oxygen levels, the magnitude of which are predicted to increase due to directional climate change. Acute changes in temperature impose physiological stress on individuals through alterations in metabolism (often quantified as aerobic metabolic scope) that affect growth, reproduction, movement, and hypoxia tolerance; and their magnitude can thus have population-level consequences. Furthermore, increases in the magnitude of acute changes in temperature and oxygen levels in estuaries may reduce the availability of suitable habitat. We used intermittent-flow respirometry to determine the effects of acute temperature changes on the metabolic scope and hypoxia tolerance of Atlantic croaker and spot; two economically and ecologically important species in Chesapeake Bay. For Atlantic croaker, metabolic scope increased from 15 to 25 °C but did not change from 25 to 30 °C, whereas metabolic scope increased from 15 to 30 °C for spot. The metabolic scope of Atlantic croaker and spot was comparable at all temperatures examined. Hypoxia tolerance, and the effects of temperature on hypoxia tolerances, did not differ by species. Our results indicate that Atlantic croaker and spot are well-adapted to the conditions they currently experience in Chesapeake Bay. Decreased availability of suitable habitat as environmental conditions continue to change will, however, result in increased competition for resources. Our results suggest that under these conditions, spot will have a competitive advantage over Atlantic croaker which may alter the dynamics of the Chesapeake Bay ecosystem.

Effects of acute temperature changes on the swimming abilities and oxygen consumption ofPtychobarbus kaznakovifrom 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 (Ucᵣᵢₜ) 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 Ucᵣᵢₜ 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.

Acute temperature effects on function of the chick embryonic heart.

We analysed the effects of acute temperature change on the beating rate, conduction properties and calcium transients in the chick embryonic heart invitro and in ovo. The effects of temperature change (34, 37 and 40°C) on calcium dynamics in isolated ED4 chick hearts invitro were investigated by high-speed calcium optical imaging. For comparison and validation of invitro measurements, experiments were also performed in ovo using videomicroscopy. Artificial stimulation experiments were performed invitro and inovo to uncover conduction limits of heart segments. Decrease in temperature from 37 to 34°C invitro led to a 22% drop in heart rate and unchanged amplitude of Ca(2+) transients, compared to a 25% heart rate decrease in ovo. Increase in temperature from 37 to 40°C invitro and in ovo led to 20 and 23% increases in heart rate, respectively, and a significant decrease in amplitude of Ca(2+) transients (atrium -35%, ventricle -38%). We observed a wide spectrum of arrhythmias invitro, of which the most common was atrioventricular (AV) block (57%). There was variability of AV block locations. Pacing experiments invitro and in ovo suggested that the AV blocks were likely caused by relative tissue hypoxia and not by the tachycardia itself. The pacemaker and AV canal are the most temperature-sensitive segments of the embryonic heart. We suggest that the critical point for conduction is the connection of the ventricular trabecular network to the AV canal.

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 (Ucrit), 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 Ucrit value decreased significantly during acute temperature changes at 5°C and 25°C; Ucrit 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.

The effect of water temperature on routine swimming behaviour of new born guppies (Poecilia reticulata).

Guppies have successfully established populations in places with thermal regimes very different from the Tropical conditions in their native range. This indicates a remarkable capacity for thermal adaptation. Given their vulnerability to predation as juveniles, acute changes in temperature, which can alter predator-prey relationships, can impact juvenile survival and have amplified consequences at the population level. To understand how temperature may impact juvenile survival and gain insight into their success as an invasive species, we researched the effect of acute temperature changes on the routine swimming behaviour of juvenile guppies. Using a novel 3-dimensional tracking technique, we calculated 4 routine swimming parameters, speed, depth, and variation in speed or depth, at 6 different test temperatures (17, 20, 23, 26, 29, or 32°C). These temperatures cover their natural thermal range and also extended past it in order to include upper and lower thermal limits. Using model selection, we found that body length and temperature had a significant positive relationship with speed. Variation in speed decreased with rising temperatures and fish swam slightly closer to the bottom at higher temperatures. All juveniles increased variation in depth at higher temperatures, though larger individuals maintained slightly more consistent depths. Our results indicate that guppies have a large thermal range and show substantial plasticity in routine swimming behaviours, which may account for their success as an invasive species.

Feeling the heat: the effect of acute temperature changes on predator-prey interactions in coral reef fish.

Recent studies demonstrate that the elevated temperatures predicted to occur by the end of the century can affect the physiological performance and behaviour of larval and juvenile fishes; however, little is known of the effect of these temperatures on ecological processes, such as predator-prey interactions. Here, we show that exposure to elevated temperatures significantly affected the predator-prey interactions of a pair of common reef fish, the planktivorous damselfish (Pomacentrus wardi) and the piscivorous dottyback (Pseudochromis fuscus). When predators exposed to elevated temperatures interacted with prey exposed in a similar manner, maximal attack speeds increased. This effect coupled with decreasing prey escape speeds and escape distances led to increased predation rates. Prey exposed to elevated temperatures also had decreased reaction distances and increased apparent looming threshold, suggesting that their sensory performance was affected. This occurred despite the increase in maximal attack speeds, which in other species has been shown to increase reaction distances. These results suggest that the escape performance of prey is sensitive to short-term increases in ambient temperature. As marine environments become more thermally variable in the future, our results demonstrate that some predators may become more successful, suggesting that there will be strong selection for the maintenance of maximal escape performance in prey. In the present era of rapid climate change, understanding how changes to individual performance influence the relationships between predators and their prey will be increasingly important in predicting the effects of climate change within ecosystems.

Effects of acute temperature changes on gut physiology in two species of sculpin from the west coast of Greenland

For a fish to thrive, the gut must function efficiently. This is achieved through a range of processes, including controlled patterns of gut motility and modifications in gut blood flow. The knowledge of how gut functions in fish are affected by environmental temperature is sparse, and in order to understand how changes in climate may affect fish populations, we need to understand how gut blood flow and gut motility are affected by changes in temperature. By simultaneous recording of gut blood flow, gut motility, cardiac output, heart rate and cardiac stroke volume, in vivo at 4, 9 and 14 °C, the acute thermal sensitivity of a thermal generalist (shorthorn sculpin Myoxocephalu scorpius) was compared to the more strictly Arctic species (Arctic sculpin M. scorpioides). Temperature effects on gut motility were further explored in vitro, using isolated smooth muscles. Elevated water temperatures increased gut blood flow and contractile activity. Contraction frequency increased nearly threefold and gut blood flow almost doubled with the 10 °C increase. Both cardiac output and heart rate increased with temperature, while cardiac stroke volume decreased. The cholinergic agonist carbachol was most potent on smooth muscles at 9 °C. There were no differences between the two species, suggesting that the gastrointestinal and cardiovascular systems of Arctic sculpin, although a more pronounced Arctic species, have similar abilities to cope with acute fluctuations in water temperature as shorthorn sculpin. The impact of increased gut activity at higher temperatures needs further investigation before the effects of climate change can be predicted.

The effects of temperature on cardiac E‐C coupling and intracellular Ca2+ buffering in trout cardiomyocytes

To investigate the effects of acute temperature change on cardiac excitation‐contraction in fish heart, atrial and ventricular myocytes were isolated from rainbow trout acclimated to 12°C and studied using voltage clamp recording while simultaneously recording [Ca2+]i at 7°C, 14°C, and 21°C. Cells were stimulated in the presence or absence of sarcoplasmic reticulum (SR) inhibitors and SR Ca2+ load and intracellular Ca2+ buffering were determined with caffeine. Atrial and ventricular cells showed increased ICa density, faster ICa inactivation, and smaller gain at 14°C and 21°C compared to 7°C. SR inhibition was most effective at 7°C, where it decreased [Ca2+]i rise slope and amplitude by 58% and 44%, respectively, and prolonged recovery of [Ca2+]i by 1.6‐fold and decreased gain by 40%. An opposite trend emerged in ventricular cells in which SR inhibition had its largest effect at 21°C, where it decreased [Ca2+]i rise slope and amplitude by 60% and 75%, respectively, resulting in a 56% decrease in gain. Bmax for Ca2+ buffering did not differ between atrium and ventricle but was higher at 7°C (1392 ± 274 μM) than at 21°C (451 ± 274 μM) while Kd was unaffected by tissue or temperature (0.27 and 0.30 μM for atrium and ventricle, respectively). Thus, atrial myocytes show a particular sensitivity to cold and increased reliance on the SR to maintain [Ca2+]i in the face of reduce ICa, while ventricular myocytes do not. Maintained [Ca2+]i at cold temperatures in both cell types is maintained by a larger SR Ca2+ load.

Effects of rapid temperature changes on HK, PK and HSP70 of Litopenaeus vannamei in different seasons

Activities of hexokinase (HK), pyruvate kinase (PK) and levels of HSP70 were measured to evaluate the response of Litopenaeus vannamei to rapid temperature changes under controlled laboratory conditions. Shrimps were subjected to a quick temperature change from 27°C to 17°C for the summer case (Cold temperature treatment), or from 17°C to 27°C for the winter case (Warm temperature treatment). After 0.5, 1, 3, 6, 12, 24, 48, and 72 h of exposure time, shrimps were sampled and prepared for further analysis. The results showed that the effect of acute temperature changes on activities of HK was significant. Patterns of variations of the two glycolytic enzymes suggested that enzymes in the glycolysis cycle could adjust their activities to meet the acute temperature change. The HSP70 level increased in both cold and warm temperature treatments, suggesting that the rapid temperature changes activated the process of body’s self-protection. But the difference in expression peak of HSP70 might be related to the different body size and the higher thermal sensitivity to temperature increase than to temperature decrease of L. vannamei.

Grueneberg Ganglion Neurons Are Finely Tuned Cold Sensors

The Grueneberg ganglion is a newly appreciated nasal subsystem with neural connections to the olfactory forebrain, but its functional role has not been well defined. Here, we assess whether Grueneberg ganglion neurons (GGNs) function as thermosensors. By investigating the effect of acute temperature changes on the cytosolic Ca(2+) concentration of genetically labeled mouse GGNs (either gender), we demonstrate that GGNs are thermosensory neurons specialized to detect a temperature decline within a given temperature window. Furthermore, GGNs comprise a relatively homogeneous cell population with respect to temperature sensitivity. GGNs do not respond to ligands of the temperature-sensitive TRP channels TRPM8 and TRPA1, suggesting a novel mechanism for temperature sensing. One possibility is a cGMP-mediated mechanism, as GGNs express the receptor guanylyl cyclase GC-G, the cGMP-sensitive phosphodiesterase PDE2 and the cGMP-sensitive channel CNGA3. Surprisingly, Cnga3-null mice show normal cooling-induced Ca(2+) responses although cGMP-dependent Ca(2+) increases are absent in these mice. Rather, the cooling-induced Ca(2+) response of GGNs depends critically on the activity of a tetrodotoxin-sensitive voltage-gated sodium channel whereas the cGMP-dependent Ca(2+) signal does not. These findings establish the Grueneberg ganglion as a sensory organ mediating cold-evoked neural responses, possibly in conjunction with the sensing of other stress- or fear-related chemical social cues.

The effects of acute temperature change on cost of transport at maximal labriform speed in bluegill Lepomis macrochirus

The effects of acute temperature change on the cost of bluegill Lepomis macrochirus swimming were quantified. At 14 degrees C, maximum labriform swimming speed (U(lab,max)) was reduced relative to that at the acclimation temperature of 22 degrees C, but total cost of transport (T(TC)) remained unchanged. At 30 degrees C, U(lab,max) was the same as at 22 degrees C, but T(TC) was 66% greater.

Effects of acute temperature change, confinement and housing on plasma corticosterone in water snakes, Nerodia sipedon (Colubridae: Natricinae)

Body temperature affects many aspects of reptilian behavior and physiology, but its effect on hormonal secretion has been little studied, especially in snakes. Major objectives of this study were to determine if acute changes in body temperature during confinement influenced plasma corticosterone levels and if initial body temperatures upon capture in the field were related to baseline corticosterone levels in water snakes (Nerodia sipedon). Water snakes were bled upon capture in the field and after one hour of confinement in a cooled, control, or heated incubator. Since little is known about the potential metabolic changes in response to stress in reptiles, plasma triglyceride levels were also measured. Upon completion of the field study, snakes were housed for 5-8 days without food to determine the effect of chronic stress on both corticosterone and triglyceride levels. Plasma corticosterone concentrations were measured using enzyme-linked immunosorbant assay (ELISA) and plasma triglycerides were determined enzymatically. In the field, experimental alterations of body temperature during confinement had no effect on corticosterone levels. Similarly, there was no correlation between initial body temperature and baseline plasma corticosterone concentrations. However, post-confinement corticosterone levels were approximately three-times greater in females than males. Plasma triglyceride levels were not affected by temperature treatment, confinement, or sex. Compared to field values, both baseline and post-confinement corticosterone levels were elevated after the chronic stress of short-term laboratory housing but triglyceride levels decreased. Overall, these results indicate that sex but not body temperature has a major influence on the adrenocortical stress response in Nerodia sipedon.

Indicators of oxygen- and capacity-limited thermal tolerance in the lugworm Arenicola marina

Thermal tolerance windows were investigated in lugworms Arenicola marina (L.) from the North Sea, the English Channel and the Atlantic during winter and summer seasons. We adopted the concept of oxygen- and capacity-limited thermal tolerance and tested a variety of methods for their suitability to identify characteristics of the respective thermal window, such as critical, pejus (lat.: getting worse) and optimum temperatures (Tc, Tp and Topt), as well as temperature-dependent perfor- mance. First, the effect of acute temperature changes on oxygen consumption and pumping activity was examined in artificial burrows ventilated by lugworms collected in winter and summer from North Sea mudflats (acclimation temperatures 5 and 10°C). Second, the window of acutely temperature- dependent growth was evaluated by following the integration of uniformly labelled 13 C-L-phenylala- nine into proteins of the cuticulo-muscular tube, using nuclear magnetic resonance spectroscopy, possibly providing access to Tp values. Third, seasonal changes in haemoglobin half-saturation oxy- gen tension (P50) and haemoglobin oxygen status in vivo were studied in lugworms from the North Sea population. Tc values were defined by use of oxygen consumption measurements, whereas pumping activity, growth performance and tissue oxygenation allowed determination of Topt. Our results show that the thermal window of actively ventilating lugworms is narrower in winter than in summer. The acute optimum temperature of growth performance was tilted towards the lower Tc and likely shifts with acclimation. Methods were found suitable to identify the acute thermal window of oxygen-limited thermal tolerance in the lugworm. Consecutive comparison of populations during various seasons in a latitudinal cline should thus lead to a better understanding of the impacts of climate change on marine ecosystems.

The effects of acute temperature change on swimming performance in bluegill sunfishLepomis macrochirus

Many fish change gait within their aerobically supported range of swimming speeds. The effects of acute temperature change on this type of locomotor behavior are poorly understood. Bluegill sunfish swim in the labriform mode at low speeds and switch to undulatory swimming as their swimming speed increases. Maximum aerobic swimming speed (U(max)), labriform-undulatory gait transition speed (U(trans)) and the relationships between fin beat frequency and speed were measured at 14, 18, 22, 26 and 30 degrees C in bluegill acclimated to 22 degrees C. At temperatures below the acclimation temperature (T(a)), U(max), U(trans) and the caudal and pectoral fin beat frequencies at these speeds were reduced relative to the acclimation level. At temperatures above T(a) there was no change in these variables relative to the acclimation level. Supplementation of oxygen levels at 30 degrees C had no effect on swimming performance. The mechanical power output of the abductor superficialis, a pectoral fin abductor muscle, was measured in vitro at the same temperatures used for the swimming experiments. At and below T(a), maximal power output was produced at a cycle frequency approximately matching the in vivo pectoral fin beat frequency. At temperatures above T(a) muscle power output and cycle frequency could be increased above the in vivo levels at U(trans). Our data suggest that the factors triggering the labriform-undulatory gait transition change with temperature. Muscle mechanical performance limited labriform swimming speed at T(a) and below, but other mechanical or energetic factors limited labriform swimming speed at temperatures above T(a).

Stress responses to rapid temperature changes of the juvenile sea cucumber (Apostichopus japonicus Selenka)

Activities of hexokinase (HK), pyruvate kinase (PK), superoxide dismutase (SOD) and catalase (CAT) and Hsp70 level were measured to evaluate the response of the commercially important sea cucumber (Apostichopus japonicus Selenka) to rapid temperature changes in laboratory. Animals were subjected to a higher temperature (from 10 to 20°C) (Tinc treatment) or to a lower temperature (from 20 to 10°C) (Tdec treatment) for 72h. At 1, 3, 12, 24, 72h of exposure, animals were removed and prepared for further analysis. Results showed that the effect of acute temperature changes on enzyme activities was significant. In Tinc treatment, activities of SOD and CAT increased immediately. The significant enhancement of SOD and CAT activities suggested that oxidative stress increases significantly when ambient temperature increasing from 10 to 20°C. The up-regulation of Hsp70 in Tinc and Tdec treatments indicated that Hsp70 was a bioindicator of thermal stress in the sea cucumber, and the expression pattern depended on the thermal treatment.

The Effects of Acute Temperature Change on Prey Capture Kinematics in Largemouth Bass, Micropterus Salmoides

The effects of temperature on prey capture kinematics were investigated in the Largemouth Bass, Micropterus salmoides. Five individuals were first acclimated to 22 C and then acutely exposed to temperatures of 15, 20, 25, and 30 C. At each temperature, feeding events were recorded using high-speed video at 500 frames s−1. An analysis of variance on the five fastest feeding events from each individual at each temperature resulted in a significant trend for the fastest feeding events to occur at 25 C. This effect confirmed the expectation of thermal dependence of mouth opening movements, which was based on an inverse relationship between water viscosity and temperature and the assumption that temperatures outside optimum decrease muscular power and contraction rates. However, the Q10 value between 15–25 C was only 1.28, well below the minimum expected value of 2.0. Thus, we suggest the possibility that Largemouth Bass partially compensate for the effects of acute temperature changes by recruiting additional motor units at lower temperatures. The capacity of Largemouth Bass to mitigate the impact of acute temperature change on muscle physiology and the physical properties of water may represent a physiological adaptation to a predatory lifestyle in a thermally variable environment.